Appendix 1 of Lutty, Mol Vis 2006; 12:532-580.


Appendix 1. Abstracts presented at the ROP Symposium

The following abstracts were selected for poster presentation, and the posters were available to Symposium attendees throughout the meeting. Authors attended posters during specified break sessions.


Poster 01:

Digital imaging in retinopathy of prematurity: Bascom Palmer Eye Institute experience 1997-2003

Audina Berrocal, Elias C. Mavrofrides, Ditte Hess, Roseanne Johnson

Bascom Palmer Eye Institute, University of Miami, Miami, FL
 

Purpose: The purpose of this project is to summarizeand share the experience of BCEI with digital imaging of premature infants at risk for ROP over the past six years employing the Retcam 120.

Methods: Infants at risk for ROP have had digital images taken as part of their routine ophthalmic examination. This practice has required close cooperation between the ophthalmologist, ophthalmic photographer and neonatal nurse.

Results: Over the six year interval some 300 hundred infants have had digital images taken with the wide angle contact camera for a total of 600 images. This practice has proven safe and effective with no complications to the eye or infant over the interval 1997 to 2003. Images are taken at the first examination and as required as the disease develops. Threshold is documented by imaging. Pre- and post-laser images are taken routinely. Examples of images of the type of lesions seen in ROP will be displayed with this poster.

Conclusions: Digital imaging has proven in the hands of an experienced team of photographer, doctor and nurse to be a useful adjunct in the management of ROP.


Poster 02:

Alleviation of oxygen-induced retinopathy in the newborn rat by retinoic acid

X. I. Couroucli, l. Kong, W. Jiang, Y. Wei, B. Moorthy

Department of Pediatrics, Baylor College of Medicine, Houston, TX
 

Supplemental oxygen administration, which is frequently encountered in the treatment of premature infants suffering from respiratory distress, contributes to the development of retinopathy of prematurity (ROP) in these patients. Retinal capillary damage caused by exposing the retina to high oxygen tensions is an early initiating event, leading to retinal vascularization and the development of proliferative retinopathy. There is accumulated evidence that vascular endothelial growth factor (VEGF) plays an important role in oxygen-mediated abnormal vessel proliferation that is observed in ROP. In this investigation, we tested the hypothesis that neonatal exposure of rats to a combination of all-trans retinoic acid (RA) and hyperoxia would alleviate retinopathy in these animals, compared to those exposed to hyperoxia only, and that modulation of VEGF expression contributes to the retinoprotective effects of RA. Newborn Fisher rats were maintained in room air or exposed to hyperoxia (greater than 95% O2) for seven days. Some animals were treated intraperitoneally with RA (0.5 mg/kg) or vehicle (saline), once daily for five days. Animals were sacrificed 1 or 30 days after termination of hyperoxia, and retinopathy was assessed by histological analysis of the retina. VEGF mRNA expression was studied by in situ hybridization. Exposure of animals to hyperoxia alone for seven days showed reduced number of retinal vessels, many of which were constricted, at 1 day compared to those breathing room air, and there were no significant differences in the retinal pathology of animals that were given RA+ hyperoxia. At this time, hyperoxia significantly upregulated retinal VEGF expression compared to those given RA+ hyperoxia. At 30 days, the oxygen-exposed animals displayed formation of new retinal vessels, whereas animals given RA+ hyperoxia showed significantly lesser extent of neovascularization. Similar to 1 day, at 30 days, VEGF expression in the hyperoxia group was much higher than that of the RA+ hyperoxia group. In conclusion, the results of our study support the hypothesis that RA protects animals from oxygen-induced retinopathy, and that downregulation of VEGF expression contributes to the retinoprotective effects of RA.


Poster 03:

Rats are not all created equal when dealing with postnatal hyperoxia

Allison Dorfman,1,2 Sandrine Joly,3 Hakima Moukhles,3 Sylvain Chemtob,1 Pierre Lachapelle2,4,5

Departments of 1Pharmacology and Therapeutics, 4Ophthalmology, and 5Neurology-Neurosurgery, McGill University, Montreal, Canada; 2Montreal Children's Hospital Research Institute, Montreal, Canada; 3Départment de Biologie, University De Montréal, Montreal, Canada
 

Purpose: In a previous study we showed that following postnatal hyperoxia the erg of pigmented Long Evans (LE) rats was more affected than that of the albino Sprague Dawley (SD) rats. This would indicate that melanin pigment might not have the protective (antioxidant) effect previously suggested. The purpose of this study was to further investigate this discrepancy.

Methods: Newborn pigmented Long-Evans (LE) and albino Sprague Dawley (SD) rats were exposed to 22.5 h of 80% O2 interrupted by 3 periods of 0.5 h at 21% O2. Scotopic (intensity: -6.3 to 0.6 log cd-s/m2; 12 h dark adaptation) and photopic (intensity: 0.9 log cd-s/m2; background: 30 cd-s/m2). ERGs were obtained at postnatal days 30 and 60. Retinal sections (enucleation at 60 days, 0.7 μm sections, toluidine blue staining) were studied as well.

Results: At 30 days of age, LE rats exposed to hyperoxia in the first week of life (0-6) showed no change in the scotopic ERG a-wave compared to a 30% reduction in the second week of life (6-14, 9-14) and 50% for exposure which included the first two weeks of life (0-14), a feature not observed in SD rats. Amplitudes were further decreased in LE rats by 30-40% (all exposure regimens) at 60 days. The rod vmax in LE rats decreased by 20% for animals exposed in the first week of life and by 85% for those exposed in the second week of life. Rod vmax amplitude in SD rats decreased only in the second week of life by 70%. No further significant changes occurred in either strain at 60 days. In contrast, the photopic b-wave, which was reduced by 85% after exposure from 0-14 at 30 days, showed an amplitude recovery (60% gain) at 60 days in le rats which was not observed in SD rats. Histological analysis at 60 days in LE rats revealed a thinning of the OPL (normal: 15.75±0.10 μm; 0-14: 2.8±1.46 μm; p<0.05); INL (normal: 32.5±0.52 μm; 0-14: 7.52±0.84 μm; p<0.05, reduced from 4.71±0.58 μm cells thick (normal) to 2.8±1.2 μm (0-14); p<0.05); IPL thickness (normal: 70.2±0.78 μm; 0-14: 26.24±1.5 μm; p<0.05). Only the OPL was reduced in SD rats (normal: 13.10±0.12; 0-14: 2.77±1.46).

Conclusions: We have previously shown that OIR in SD rats did not evolve with time, where structural and functional anomalies remained the same at 30 and 60 days. In contrast, OIR in LE rats is much more severe and shows signs of functional deterioration over time, indicative of a different pathophysiological process in the two strains. Furthermore, the structural anomaly in SD rats is limited to the OPL, whereas it is more extensive in LE rats involving the OPL in addition to the INL and IPL. Whether this difference can be attributed to a strain difference or to the presence of melanin pigment will be fully elucidated using another rat model. The above knowledge will be instrumental both for future laboratory as well as clinical studies of ROP. Funded by: CHR and Réseau Vision


Poster 04:

Screening and treatment experience at Jackson Memorial Hospital/Bascom Palmer Eye Institute 2002-2003

Elias C. Mavrofrides, Audina M. Berrocal, Timothy G. Murray, Ditte Hess, Roseanne Johnson

Bascom Palmer Eye Institute, University of Miami, Miami, FL
 

Purpose: To review the results of ROP screening at a busy neonatal intensive care unit over a 13 month period.

Methods: Retrospective chart review.

Results: We screened 224 premature infants over a 13 month period. Eighty-five (38%) of these infants developed some form of ROP. Threshold ROP requiring laser therapy occurred in 25 (29% of infants with ROP). Of the infants 25 weeks or less, 41/42 (98%) developed ROP and 20/42 (48%) reached threshold ROP requiring treatment. Infants 26-28 weeks, 36/86 (41%) developed ROP and 3/86 (3.5%) reached threshold. Infants 29 weeks or more, 8/96 (8.3%) developed ROP and 2/96 (2.1%) reached threshold. All infants undergoing laser therapy were less than 850 g at birth. Infants 750 g or less had a 42% (22/53) chance of requiring laser therapy for threshold disease. Of the infants undergoing laser therapy, 4/25 (8%) required more than one session. Two (2/25) of the treated infants progressed and required surgical intervention. In both cases laser treatment was delayed because of medical instability.

Conclusions: Advances in neonatal care have increased the survival of extremely premature and very low birth weight infants. These infants show high risk for the development of ROP and progression to threshold. Good outcomes can be achieved with aggressive screening and treatment.


Poster 05:

Persistent ridge neovascularization after laser treatment in threshold ROP

Elias C. Mavrofrides, Audina M. Berrocal, Ditte Hess, Roseanne Johnson

Bascom Palmer Eye Institute, University of Miami, Miami, FL
 

Purpose: To show by digital imaging the importance of treatment adjacent to the ridge in a case of persistent neovascularization after laser treatment.

Methods: Case report.

Results: A patient showed an area of persistent ridge neovascularization despite near confluent laser treatment. There was a localized skip area just anterior to the ridge in the area of persistent activity. Re-treatment with laser photocoagulation to this skip area resulted in prompt resolution of the neovascular process.

Conclusions: Localized skip areas can result in persistent ridge neovascularization especially if located along the anterior aspect of the ridge. Re-treatment with laser photocoagulation can effectively manage this persistent activity. Digital imaging can be useful in monitoring such cases.


Poster 06:

Retinopathy of prematurity in Denmark: has progress reached a plateau?

Hans Fledelius

Rigshospitalet Eye Department, Copenhagen, Denmark
 

Purpose: The aim is to update regarding surveillance for ROP in Denmark, and to analyze whether the continuous improvement over 20 years has come to a halt.

Methods: Three information sources were scrutinized: (1) fresh data, on a national basis (population 5.3 mio) from the compulsory register of childhood visual impairment (n=106, age 0-17 years). (2) selected premature infants who had their primary care, to include early eye exams, in the tertiary unit of the Copenhagen University Hospital 1997-2001 (n=453 survivors). (3) truly epidemiological data from Frederiksborg County 1982-2001 (n=1123 under surveillance; population now 370.000, with 4.400 liveborn annually).

Results: Over 20 years prematures' ROP statistics have continuously improved. In the national visual impairment register, on average the annual number of new cases has fallen from 8 to 3.5 per year, and the share of heavy blindness (<=1/60) from 68 to 19%. Further, for those regionally with ROP there has been a steady fall in the median values for GA/BW, from 30 week/1348 g in the 1980s to a present value of 27 week/816 g, and "heavy" prematures (>1500 g) now escape developing ROP. However, we should also emphasize a possible change of events. 17 cases of the birth cohort 2001 thus had cryo/diode laser treatment in the university clinic (centralized, on a national basis), a significant rise from the usual frequency of 5-9 cases of therapy-demanding threshold stage 3 ROP. Further, in the unselected county sample there was a turn of the nice curve hitherto observed. From a bottom value of 10% among those of a GA/BW <32 week/1750 g in the previous 4-year period, the ROP frequency (any grade) returned to 31% for birth years 1998-2001, and referrals for retinal ablation therapy were 0 and 4, respectively.

Conclusions: More very small prematures now survive, but relatively less ROP is encountered. Small figures should be interpreted with caution, but the possible trend towards less positive results stresses the demand of continuous evaluation of our screening efforts.


Poster 07:

Atypical morphology in retinopathy of prematurity

Anna L. Ells, Leslie Mackeen

Institute of Maternal & Child Health, Department of Pediatrics, University of Calgary, Calgary, Alberta; Pediatric Ophthamology, Alberta Children's Hospital, Calgary, Alberta
 

Background: The diagnosis and management of retinopathy of prematurity (ROP) depends on recognition of various stages of the disease. The morphology of the ROP lesion changes with advancing stage and severity.

Methods: The Retcam-120 digital camera system equipped with an ROP lens, 80° lens, and high magnification lens was used to document atypical ROP morphology within its various stages.

Results: The following ROP lesions will be presented: Iris neovascularization, Vitreous organization, Dragging of ciliary processes, Sinusoids, Popcorn, Aggressive-posterior ROP, Notches, Lacunae, Choroidal infarcts, and Tunica vaculosa lentis.

Conclusions: We have imaged atypical ROP lesions, which may be critical to diagnosis and timing of intervention


Poster 08:

Systemic manifestation in response to mydriasis and physical examination during screening for retinopathy of prematurity

S. Rush, R. Rush, J. Nicolau, K. Chapman, M. Naqvi

Department of Pediatrics, Texas Tech University Health Sciences Center and Northwest Texas Healthcare Systems, Amarillo, TX
 

Purpose: To determine if vital sign changes during the retinopathy of prematurity (ROP) screening examination are due to: pharmacological properties of eye drops or physical manipulation of the eye.

Design: A prospective observational study in which infants weight <=1500 g or <=32 week gestational age admitted to two university affiliated hospitals were enrolled. A total of 32 infants participated in this study. Blood pressure, heart rate, temperature, respiratory rate, and oxygen saturation were recorded at different intervals during the ROP screening.

Results: Heart rate, oxygen saturation following the physical manipulation of the eye were statistically significant different from the base line. There was also a significant difference in the vital signs during the instillation of the ophthalmological drops.

Conclusions: Regardless of gesational age, the infants demonstrated significant distress during the eyelid speculum examination. Ophthalmologist should attempt to perform this part of the examination as promptly as possible using topical anesthetics.


Poster 09:

Effects of comfort care in pain response in preterm infants undergoing screening for retinopathy of prematurity

R. Rush, S. Rush, F. Ighani, B. Anderson, M. Irwin, M. Naqvi

Department of Pediatrics, Texas Tech University Health Sciences Center and Northwest Texas Healthcare Systems, Amarillo, TX
 

Purpose: The aim of the study was to determine if pain and distress during the retinopathy of prematurity (ROP) screening examination could be ameliorated by providing comfort care.

Design: A prospective, randomized, controlled trial of thirty stable preterm infants who underwent initial ROP screening examination. Fourteen study infants were swaddled, held, and given 24% sucrose solution during the examination. Sixteen controls were examined while laying in their cribs. Vital signs (i.e., Pulse rate, respiratory rate, and oxygen saturation), crying time, and the time for the vital signs to return to baseline were recorded at different intervals during the examination.

Results: The vital signs did not vary significantly between the two groups. The participants in the control group showed a trend of longer crying time, but it did not reach a level of statistical significance. The amount of time required for the vital signs to return to their baseline values also did not vary significantly.

Conclusions: ROP screening is very distressful for the preterm infant. The routine use of comfort care during the ROP screening examination may not be sufficient to reduce pain and distress in preterm infants.


Poster 10:

Screening of Norrie disease gene mutations in retinopathy of prematurity

Terri L. Young, Kelly A. Hutcheson, Graham E. Quinn, Monte D. Mills, Jamie Koh, Prasuna C. Paluru

Departments of Ophthalmology and Pediatrics, and the Duke University Eye Center, Duke University, Chapel Hill, NC
 

Purpose: Norrie disease is an x-linked recessive disorder characterized by variable hearing loss and mental retardation, and bilateral retinal detachments. Norrie disease gene (NDP) polymorphisms primarily limited to exon 3 have been associated with heritable retinal vascular disorders, and in a small subset of patients with severe retinopathy of prematurity (ROP). We sought to correlate severity of ROP disease to ndp mutations in a large cohort of premature infants performing a mutation screen of the entire 3-exon gene. Parental carrier status was also evaluated.

Methods: A total of 118 individuals of different ethnic backgrounds were consented and screened: 87 were pre-term infants and 31 were parents. Of the 87 infants, 52 had severe ROP of stages 3-5 (15 prethreshold, 33 threshold, 1 stage 4b, 3 stage 5). The mean gestational age was 28.5 week (range 23-34), and the mean birth weight was 1062.5 g (range 367-1758 g). Seven primer pairs delineating overlapping amplicons spanning NDP were optimized for denaturing high performance liquid chromatography sequence screening and direct sequencing analysis. Three amplicons covered the coding region, and the remaining four spanned the 3' untranslated (UTR) region.

Results: Two sequence alterations were found, both in the 3' UTR region of exon 3. A g->a polymorphism at mRNA position 824 was found in an African American female and male with prethreshold and threshold ROP, respectively. An a->g polymorphism at mRNA position 1103 was found in an African American male with threshold ROP and in his normal mother, who was heterozygous for the polymorphism.

Conclusions: Two novel nucleotide changes were found in the 3' UTR region of exon 3 in our cohort. This is of interest, as African American infants are generally less likely to develop severe levels of ROP. The results suggest that no association exists between NDP mutations and severity of disease in a large cohort of infants with ROP.

Support: The Blind Children's Center Fund, Research to Prevent Blindness, Inc., and the Mabel E. Leslie Funds


Poster 11:

A specific elevated cytokine profile is associated with development of severe retinopathy in very low birth weight infants

Michael D. Neufeld, Michelle A. Williams, Christine A. Gleason

Departments of Pediatrics and Epidemiology, University of Washington, Seattle, WA
 

Purpose: To test the hypothesis that elevated serum cytokine levels at birth and/or during the first several weeks of life are associated with an increased risk of developing severe retinopathy of prematurity (ROP).

Background: Elevated cytokine levels have been associated with increased risk for various neonatal diseases including respiratory distress syndrome, chronic lung disease, and brain injury. Cytokines have an important role in angiogenesis through the stimulation of VEGF production. Specific cytokine patterns have not previously been related to development of ROP, a disorder whose hallmark is abnormal angiogenesis.

Design: Pilot study with a prospective cohort of 14 infants <1500 g born at the University of Washington Medical Center (Seattle, WA). At delivery, cord blood was obtained and analyzed for stnfr(p55), IL-1b, and IL-6 and IL-8. In the neonate, plasma was obtained within 3 h of birth and at 12, 24, 48, and 72 h after birth and weekly for six weeks and analyzed similarly. Plasma was also obtained for analysis whenever infection was suspected. Data was collected regarding ROP beginning at the first retinal examination, which occurred at age six weeks.

Results: General cytokine profiles revealed a peak in stnfr(p55) levels within 3 h of birth that returned to the birth level by about 48 h. In infants that did not develop stage 3 ROP, stnfr(p55) levels continued on a gradual downward trend. However, in infants that did develop stage 3 ROP, stnfr(p55) levels had a second peak at two weeks after birth and remained elevated when compared to those infants that did not develop stage 3 ROP. The other three inflammatory cytokines (IL-1b, IL-6, and IL-8) returned to baseline after an initial early peak. However, IL-1 beta and IL-6 had similar peaks at two weeks after birth in infants that later developed stage 3 ROP whereas there was no peak at 2 weeks in infants that did not develop stage 3 ROP.

Conclusions: Our findings support the hypothesis that inflammatory cytokines at two weeks of age are associated with a greater risk of developing severe ROP. We speculate that one mechanism for this association may be the stimulation of production of VEGF in the retina by circulating inflammatory cytokines.


Poster 12:

VEGF isoforms and PEDF mRNA expression in a rat model of ROP

Janet R. McColm, Mary Elizabeth Hartnett

Department of Ophthalmology, University of North Carolina, Chapel Hill, NC
 

Purpose: To investigate the VEGF isoforms and PEDF expression in a rat model of ROP.

Methods: A well defined rat model of ROP was used that cycled oxygen between 50% and 10% every 24 h for 14 days. Newborn litters were subjected to this oxygen regime and then removed to room air. Retinas were dissected from the animals and either flat mounted and stained with Griffonia lectin to visualize the vasculature, or were placed into RNAlater for rt-PCR. VEGF isoforms (120, 164, and 188) and PEDF were detected and 18S RNA used as a control.

Results: As previously described in this model of cycled oxygen, at P14 all animals had an avascular peripheral retina (mean 30% avascular) and all animals developed neovascularization at P18, with resolution by P25. VEGF mRNA was detectable at all times and for all isoforms. In both groups VEGF164 was the predominantly expressed isoform. In controls groups VEGF164 expression remained constant, however in the experimental group at P7 (immediately after 24 h of hyperoxia) it was reduced (by a factor of 1.6), at P14 (immediately after 24 h of hypoxia) it was elevated (by a factor of 1.6) and remained so through day 18 (by a factor of 1.4). PEDF was also detectable in all samples. In the control groups its expression remained low and constant, and in the experimental group it was elevated at all times compared to controls. However the oxygen cycling affected its expression; it was elevated at P7 (after hypoxia by a factor of 2) but this dropped to a factor of 1.4 at P14 and P18.

Conclusions: Animals raised in a variable oxygen express VEGF164 and PEDF differently from room air raised animals, with periods of hyperoxia resulting in down-regulation of VEGF and upregulation of PEDF and periods of hypoxia resulting in the opposite effect. These growth factors are known to be important in angiogenesis and their dysregulation compared to controls in this animal model may explain at least some of the changes seen in retinal blood vessel development.


Poster 13:

Comparison of retinal outcomes after lens-sparing vitrectomy or scleral buckle for stage 4 retinopathy of prematurity

M. Elizabeth Hartnett, Srilakshmi Maguluri, Hilary Thompson

Department of Ophthalmology, University of North Carolina, Chapel Hill, NC
 

Purpose: To compare anatomic outcomes after lens-sparing vitrectomy (LSV) or scleral buckle (SB) for stage 4 retinopathy of prematurity (ROP) and to test the hypothesis that vitrectomy stops progressive stage 4 ROP.

Methods: Nonrandomized, retrospective study of infants consecutively managed for stage 4 ROP by LSV or SB. Outcomes were retinal attachment within one month of initial surgery and at the end of follow-up and number of procedures to achieve retinal attachment. Exact χ2 methods determined significance and Student's t-test compared mean post-menstrual age and birth weight between the groups.

Results: After one procedure, LSV was associated with retinal attachment more often compared to SB (p=0.0341). LSV required only one surgical procedure compared to SB (p=0.0003). There were no differences between the surgical groups by mean post-menstrual age and birthweight (Student's t-test, p>0.05), or to severity of ROP determined by zone, clock-hours of ridge elevation or quadrants of plus disease.

Conclusions: This study supports the hypothesis that vitrectomy stops progressive stage 4 ROP. LSV was associated with retinal attachment more often than SB. Further prospective analysis can determine the effects of LSV and SB on visual development in progressive stage 4 ROP.


Poster 14:

The influence of Pacific race, sex, and ability to cry at 31 week exam, on threshold ROP

Dustin Lang, Jon Blackledge, Robert W. Arnold

Department of Ophthalmology, Providence Hospital, Anchorage, AK
 

Background: African-American race affords some protection from ROP but we previously noted more ROP in another darkly pigmented race, the Alaskan native (JPOS 31:192-4, 1994).

Methods: From fall 1989 through summer 2003, all Alaskan infants with birthweight <1500 g were examined by RWA documenting mothers stated race, prenatal care, and NICU course. After 1992, at the 31 week initial ROP screening, we recorded whether the infant was able to cry (cry), did Not cry (quiet), or was intubated (vent) during indirect ophthalmoscopy With lid speculum and see-through (Storz sp7-38098) scleral depression.

Results: ROP was classified as to threshold (Stage 3, zone 1-2, plus) in 873 infants. Threshold ROP was more common in Alaska natives but also for Asians (χ2=48, p<0.0001) and there was no significant difference between Alaska natives and Asians (p=0.24). Alaskan native males had more threshold ROP (Chi square (197,1)=7.8, p=0.005). Compared to threshold non-natives, Alaskan native threshold infants had greater birthweights (t=2.9, p=0.005), required less time on ventilation (F81,4=4.2, p=0.004) and were younger at age of treatment (F89,4=3.7, p=0.008). Infants who were able to cry during their 31 week GA screening exam were less likely to progress to threshold (χ2=36, p<0.001). Using a logistic fit of threshold, the increased risk of ROP in infants unable to cry persisted independent of gestational age or birthweight.

Conclusions: The consistently increased risk of threshold ROP in Alaska Natives may be related to ancestry across the Bering Sea land bridge. Threshold Alaskan natives had similar or better prenatal and NICU variables than threshold non-natives but native males had the worst risk. Infants unable to cry during the first screening exam were at Increased risk to progress to threshold ROP.


Poster 15:

Health related quality of life at age 10 years in very-low-birth-weight children with and without threshold retinopathy of prematurity

Ge Quinn, V. Dobson, S. Saigal, D. Phelps, R. J. Hardy, B. Tung, C. G. Summers, E. Palmer, on behalf of the Cryo-ROP Cooperative Group

Department of Ophthalmology, The Children's Hospital of Philadelphia, Philadelphia, PA
 

Purpose: Describe parental perspectives on health status and health related quality of life (HRQL) at age 10 years in children with birth weights <1251 g who participated in the multicenter cryotherapy for retinopathy of prematurity (cryo-ROP) study.

Background: Retinopathy of prematurity (ROP) is a significant morbidity of extreme prematurity and can have lifelong impact on general well-being.

Methods: In 244 participants in the randomized cryo-ROP trial and 102 cryo-ROP participants who did not develop ROP, the health utilities index (HUI3) system was used to characterize health status for eight attributes: vision, hearing, speech, ambulation, dexterity, emotion, cognition, and pain. Using a utility formula, HRQL was determined for each child on a scale from 0.0 (dead) to 1.00 (perfect health).

Results: The proportion of the ROP-randomized group with limitations in <4 attributes was 20.6% compared to 2.0% for the no-ROP group. Within the ROP-randomized group, the proportion of "sighted" children with limitations in >4 attributes was 6.4% versus 46.5% in the "blind/low vision" group. Median HRQL score for ROP-randomized children was lower than for no-ROP children (0.72 versus 0.97, p<0.001); median HRQL score for sighted-randomized children was 0.87 versus 0.27 for blind/low vision children (p<0.001).

Conclusions: Threshold ROP was associated with functional limitations in health attributes and reduction in HRQL scores at age 10 years. Furthermore, among children who developed threshold ROP, a greater reduction in HRQL scores was found among children with a poor visual outcome compared to those with better sight.


Poster 16:

Does optic nerve hypoplasia exacerbate retinopathy of prematurity?

Robert W. Arnold

Department of Ophthalmology, Providence Hospital, Anchorage, AK
 

Background: The risk of progression to threshold ROP correlates with the area of avascular retina and inversely with the degree of vascular maturity. I observed asymmetric ROP progression in two infants with optic nerve hypodevelopment.

Methods: Case 1: A 23 week gestational age (GA), 590 g birthweight Asian female progressed to Threshold posterior ROP right eye by 34 week GA. The left eye was Subthreshold and more peripherally developed. There was no history of Antenatal ethanol or drug exposure. Diode laser (928 burns) was delivered to the right eye. At that time, and confirmed in subsequent Years with EUA, the right eye had marked optic nerve hypoplasia. Refractive error at age 1 was -3.00 OD and +4.00+1.00x90° OS. Case 2: A 25 week GA, 750 g birthweight Caucasian female with prenatal ethanol and the exposure progressed to asymmetric threshold by 37 week GA. She received diode laser 2013 burns OD and 1113 burns OS. The nerves were minimally pale and the right was relatively hypoplastic with diameter 75% of the left eye.

Conclusions: Two of 90 threshold ROP cases over 13 years demonstrated asymmetric progression associated with optic nerve hypoplasia. Poor development of the nerve head seems to delay retinal vascular maturity.


Poster 17:

Cellular and molecular abnormalities of retinal blood vessel development in the (Edinburgh) variable oxygen rat model of ROP

Brian Fleck,1 Jean Wade,2 Zeenat Yacoob,2 Kofi Sedowofia,2 David Giles,2 Linda Wilson,3 Steve Cunningham,2 Janet R. Mccolm,4 Neil Mcintosh2

Departments of 1Ophthalmology, 2Child Life and Health and 3Biomedical Sciences, University of Edinburgh, Edinburgh, UK; 4Department of Ophthalmology, University of North Carolina, Chapel Hill, NC
 

Purpose: The "Edinburgh" physiological oxygen variability rat model of ROP has been used to answer clinical questions [1]. We have also used the model to study cellular and molecular abnormalities of retinal blood vessel development in ROP.

Methods: Litters of newborn rats were raised in room air or in a fluctuating oxygen environment from birth to 14 days. The oxygen profile was derived from an infant who developed threshold ROP, and was translated to fluctuate around a normoxic, hypoxic and hyperoxic mean. A modification of the Penn model [2] of fluctuating oxygen was used as a positive control; 80%:20% 12 h cycles for 14 days were used. A "resuscitation" model used an initial 10 min period of 10% oxygen followed by a 10 min period of 100% oxygen, followed by 14 days fluctuating oxygen with a mean of 8 kPa. Retinal wholemounts were prepared for immunohistochemical staining [3]. Endothelial cells (g. Simplicifolia bandeiraea isolectin B4), astrocytes (GFAP), smooth muscle cells (alpha SMA), and pericytes (desmin) [4] were studied using confocal microscopy. Western blot analysis was used to quantify alpha SMA and HIF-1 alpha proteins. In situ hybridization using DIG labeled probes was used to demonstrate mRNA for VEGF, angiopoietins 1 and 2.

Results: Abnormalities of retinal blood vessel development with peripheral avascular areas and abnormal capillary branching are shown in the accompanying poster. Abnormal terminal buds were seen at the leading edge of the developing capillary network. In the resuscitation model abnormal capillary buds were seen throughout the capillary bed. The astroctye network extended to the edge of the retina in control retinas, with the capillary network terminating just posterior to this. A peripheral avascular area was seen in retinas exposed to fluctuating oxygen at a hyperoxic mean, and the astrocyte network terminated just posterior to the capillary bed. Alpha SMA expression was slightly reduced and desmin expression was markedly reduced in retinas exposed to fluctuating oxygen. VEGF mRNA was strongly expressed in the inner nuclear layer of positive control retinas, and variably expressed in retinas exposed to fluctuating oxygen at a mean of 8 kpa and 10 kpa. Expression was greatest in the anterior, avascular retina. Angiopoeitin 1 and angiopoeitin 2 mRNA were not visualized using dig labeled RNA probes. HIF-1 alpha protein was not demonstrated in Western blot analysis.

Conclusions: The "Edinburgh" physiological fluctuating oxygen rat model of ROP produces abnormalities of retinal endothelial cells, astrocytes, smooth muscle cells, pericytes, and VEGF expression.

References:
1. Cunningham S, McColm JR, Wade J, Sedowofia K, McIntosh N, Fleck B. A novel model of retinopathy of prematurity simulating preterm oxygen variability in the rat. Invest Ophthalmol Vis Sci 2000; 41:4275-80.
2. Penn JS, Tolman BL, Lowery LA. Variable oxygen exposure causes preretinal neovascularization in the newborn rat. Invest Ophthalmol Vis Sci 1993; 34:576-85.
3. Chan-Ling T. Glial, vascular, and neuronal cytogenesis in whole-mounted cat retina. Microsc Res Tech 1997; 36:1-16.
4. Benjamin LE, Hemo I, Keshet E. A plasticity window for blood vessel remodelling is defined by pericyte coverage of the preformed endothelial network and is regulated by PDGF-B and VEGF. Development 1998; 125:1591-8.


Poster 18:

Pre-laser oxygen saturations as a predictive factor for retinopathy of prematurity (ROP) progression

Christina J. Flaxel,1,2 William J. Thomas,2 Michael Rauser,2 Jesse A. Dovich2

1Doheny Retina Institute of The Doheny Eye Institute, Los Angeles, CA; 2Department of Ophthalmology, Loma Linda University, Loma Linda, CA
 

Purpose: Evaluate differences in birthweight, gestational age and oxygen saturation of premature infants requiring laser photocoagulation versus weight-matched non-lasered premature infants.

Methods: Rretrospective chart review of all premature infants screened for retinopathy of prematurity between May 2000 and December 2001. Comparison was made between birthweight, gestational age and oxygen saturation for three weeks prior to laser in lasered infants versus these parameters in non-lasered infants before the infant reached 2500 g.

Results: As previously described, birthweight and gestational age were the most significant predictors of ROP progression. When comparing daily oxygen saturations over three weeks, we found the average oxygen saturation was less in babies that were lasered on every day prior to laser.

Conclusions: as noted in prior studies, birthweight and gestational age are the most significant predictors of ROP progression. Our data suggest that decreased oxygen saturation as early as three weeks prior to and as late as two days prior to laser in weight-matched premature infants may increase the possibility of ROP progression to the point of requiring laser photocoagulation.


Poster 19:

Telematics for ROP screening using a digital wide-angle fundus camera and custom software for data analysis

Birgit Lorenz and the Cooperative Study Group

Department of Pediatric Ophthalmology, Strabismology, and Ophthalmic Genetics, University of Regensburg, Regensburg, Germany
 

Purpose: To present the authors' experience with ROP screening using the Retcam digital wide-angle retinal camera in five neonatal intensive care units (NICUS) and as compared to the conventional assessment by a general ophthalmologist using the binocular indirect ophthalmoscope (BIO).

Methods: The study followed the tenets of the declaration of Helsinki and was approved by the ethical committee of the university of Regensburg. All infants at risk were screened according to the national guidelines. After informed consent was given, image data and BIO assessments were collected by local ophthalmologists. Encoded images were sent via telephone to the reading center and the pediatric data was sent separately via email or FAX. For standardized data evaluation software was developed allowing semi-automatic quantification of the pathologies as to zone, clock hours involved, and disease severity.

Results: Within 18 months, 249 infants were screened. All stages requiring treatment (i.e., ROP zone 2 stage 3+ and zone 1 prethreshold; 20 eyes, 10 infants) were detected from assessment of the images at the reading center. However, early or very peripheral ROP were sometimes difficult to detect from the images but these were always shown to be cases not requiring treatment.. If the screening had been conducted only from image assessment at the reading center no neonate would have been treated late. The primary issue is detection of disease requiring a detailed assessment by an on-site pediatric ophthalmologist. Measured in terms of outcomes this method of screening was shown to be 100% sensitive to "referral warranted ROP." The coding system was simple to use and reduced risks of user-related errors. The software yielded quantitative data and a graphic report of the disease stage allowing precise follow-up examinations and easy communication with the pediatricians and local ophthalmologists.

Conclusions: Screening for "referral warranted ROP" by digital imaging was demonstrated on 249 infants with 100% sensitivity. The custom software for data analysis allows a more uniform evaluation of ROP and a more precise localization and quantification of the various stages. The ease of use of the software was demonstrated.

Support: Bayerische Landesstiftung, Bayerische Sparkassenstiftung, dfg lo 457/4-1,2, the portable diode laser was generously given by Iris Medical Inc. (Mountain View, CA) and the Bayerische Sparkassenstiftung.


Poster 20:

The Edinburgh retinopathy of prematurity (ROP) model: from the NICU to the laboratory and back

Neil Mcintosh,1 Steve Cunningham,2 Janet R. Mccolm,3 Kofi Sedowofia,1 Jean Wade,1 Balasz Gellen,1 Zeenat Yaqoob,1 Brian Fleck4

1Department of Child Life and Health, University of Edinburgh, UK; 2Royal Hospital For Sick Children, Edinburgh, UK; 3Department of Ophthalmology, University of North Carolina, Chapel Hill, NC; 4Princess Alexandra Eye Pavilion, Edinburgh, UK
 

Purpose: To develop a model of oxygen variability derived from the clinical setting and to expose newborn rat pups to it. This model would allow us to examine in more detail the contributory effects of clinically relevant oxygen and carbon dioxide and to test preventative strategies and therapeutic interventions.

Background: The FiO2 breathed by preterm newborn infants is now closely controlled to maintain the PaO2 between 5-9 kPa (40-90 Torr). We do not expose babies to hyperoxia, but some still develop ROP. In a clinical case/control study [1], our group seemed to confirm Penn's data in rats [2] suggesting that oxygen variability might be more important in the production of ROP than hyperoxia and other parameters. A later clinical study using the same methodology was not able to demonstrate that the PaCO2 was important [3].

Methods: We took a minute by minute profile (recorded by computer) of tcpO2 (transcutaneous pressure of oxygen) over the first 14 days of life from a preterm infant that developed ROP. The mean level was 8 kpa (60 Torr). With Biospherix, we manufactured an incubator where we could incubate rat pups and their mothers for 14 days in exactly this oxygen environment. The rat pups developed many of the features of ROP including decreased capillary density and an immature vascular appearance, avascular areas at the periphery and tufting terminal vessels, thus validating the model. Experiments increasing the mean concentration to 10 kPa (75 Torr) yet maintaining the same variability, increased the severity of the ROP changes. Reducing the mean concentration to 6 kPa (45 Torr) while maintaining the variability almost eradicated the changes of ROP [4].

Results: A sustained 5% environmental carbon dioxide (with probably hypercapnia) with concurrent oxygen variability produced the most severe ROP of all our models with increased capillary density, increased avascularity and a higher proportion of retinas showing neovascularization.

Conclusions: Back to the NICU: Now the northern neonatal group of the UK [5] and the NICHD neonatal research network in 2002 [6] have both published epidemiological data showing that the lower units run their oxygen saturation alarms, the lower the incidence of ROP. Chow has also shown that scrupulous NICU management to reduce oxygen variability has also reduced the incidence of ROP [7].

References:
1. Cunningham S, Fleck BW, Elton RA, McIntosh N. Transcutaneous oxygen levels in retinopathy of prematurity. Lancet 1995; 346:1464-5.
2. Penn JS, Henry MM, Tolman BL. Exposure to alternating hypoxia and hyperoxia causes severe proliferative retinopathy in the newborn rat. Pediatr Res 1994; 36:724-31.
3. Gellen B, McIntosh N, McColm JR, Fleck BW. Is the partial pressure of carbon dioxide in the blood related to the development of retinopathy of prematurity? Br J Ophthalmol 2001; 85:1044-5.
4. McColm JR, Cunningham S, Wade J, Sedowofia K, Gellen B, Sharma T, McIntosh N, Fleck BW. Hypoxic oxygen fluctuations produce less severe retinopathy than hyperoxic fluctuations in a rat model of retinopathy of prematurity. Pediatr Res 2004; 55:107-13.
5. Tin W, Milligan DW, Pennefather P, Hey E. Pulse oximetry, severe retinopathy, and outcome at one year in babies of less than 28 weeks gestation. Arch Dis Child Fetal Neonatal Ed 2001; 84:F106-10.
6. Anderson CG, Benitz WE, Madan A. Retinopathy of prematurity (ROP) and pulse oximetry: a national survey of recent practices. Pediatr Res 2002; 51:367A
7. Chow LC, Wright KW, Sola A, CSMC Oxygen Administration Study Group. Can changes in clinical practice decrease the incidence of severe retinopathy of prematurity in very low birth weight infants? Pediatrics 2003; 111:339-45.


Poster 21:

Minimal anesthesia using glucose gel on a pacifier combined with oral acetaminophen for laser ablation of the avascular retina in threshold retinopathy

Khaled A. Tawansy, Melinda Hakim, Eugene De Juan

Department of Ophthalmology, Children's Hospital of Los Angeles, Los Angeles, CA
 

Purpose: Can respiratory depression in neonates attributable to use of narcotics or sedatives during retinal laser procedures be minimized by a novel anesthetic protocol that incorporates concentrated glucose, oral acetaminophen, and the suckle response?

Background: Glucose gel painted on a pacifier in combination with oral acetaminophen provides sufficient anesthesia and analgesia to allow laser ablation of the avascular retina in many neonates with threshold ROP.

Methods: This is a prospective, consecutive clinical series of 40 neonates with bilateral threshold retinopathy of prematurity managed in the NICU by the retina service at a major children's hospital. Entry criteria included absence of mechanical ventilation for the proceeding 48 h and a reliable suckle response. Ablation was performed in a near-confluent pattern between the edge of neovascularization and the ora serrata using a Diode binocular indirect laser, 28 D condensing lens, wire lid speculum, and Flynn depressor. The baby was kept fasting for five hours, and then received a pacifier painted with glucose gel and oral acetaminophen (15 mg/kg). Additional medications included topical tetracaine and oxygen by nasal cannula in all cases and topical or intravenous atropine in babies with a prominent vagal response. Pain was evaluated subjectively by a nurse observer and objectively by vital sign recordings.

Results: All 40 patients received laser ablation without the use of narcotics or sedatives. In five patients, initial treatment was limited to one eye due to the child developing restlessness or a sustained rise in heart rate greater than 200 beats/min. The second eye was treated uneventfully the following day using a similar technique. None of the neonates suffered significant respiratory depression or required mechanical ventilation during the treatment. One patient was intubated approximately 12 h after laser for RSV pneumonia. Between 450 and 1,400 laser burns were placed in each eye, with settings of 200 to 500 mW and 300 to 500 ms. Re-treatment using the same technique was required from 7 to 20 days later due to persistence or recurrence of vascular activity in 16 eyes of 14 patients with predominately zone 1 or posterior zone 2 disease. Nineteen eyes went on to stage iv and were managed with either lens-sparing vitrectomy (n=14), or scleral buckling (n=5).

Conclusions: In many neonates with threshold ROP and absence of major cardiopulmonary compromise, suckling of a pacifier painted with concentrated glucose in combination with oral acetaminophen appears to create a transient state of anesthesia and anelgesia sufficient to permit laser ablation of the peripheral retina at the bedside with minimal respiratory complications.


Poster 22:

Antenatal and perinatal risk factors for significant (stage 3 or 4) retinopathy of prematurity in the Australian and New Zealand neonatal network

Jolie Hutchinson,1 Brian Darlow,2 Judy Simpson,3 Deborah Donoghue,1 David Henderson-Smart,1 Nick Evans,4 on behalf of the Australian and New Zealand Neonatal Network (ANZNN)

1Centre For Perinatal Health Services Research, University of Sydney, Australia; 2Department of Paediatrics, Christchurch School of Medicine, Christchurch, New Zealand; 3School of Public Health, University of Sydney; 4RPA Women's and Babies, Sydney, Australia
 

Purpose: To identify antenatal and perinatal risk factors for significant (stage 3 or 4) retinopathy of prematurity (ROP), which may then be used to adjust for case-mix in studies of variations in the rate of significant ROP between neonatal intensive care units.

Methods: Data were collected prospectively as part of the ANZNN's ongoing audit of all high-risk infants (BW <1500 g or gestation <32 week) admitted to each of the 28 level iii NICUS in Australia and New Zealand. Twenty-three maternal, antenatal and perinatal variables up to and including 1 min of age were examined in the subset of infants born at <29 week during a two year period (1998-99), who survived to 36 weeks post-menstrual age and were examined for ROP: n=2111. Univariate analysis to detect potential risk and protective factors for stage 3 or 4 ROP was undertaken and those variables not significant at p<0.05 were eliminated. These variables were then entered in stepwise fashion into a multivariate logistic model and rejected when they lost significance at p<0.01.

Results: Four factors remained in the model after simultaneous adjustment: gestation, gender, weight less than the 10% percentile for gestational age (SGA) and APGAR at one minute <4 (apg1). However, there was a strong relationship between apg1 and gestation such that the odds ratio for gestation changed markedly when both variables were included in the model but with very little change in the predictive power. Since it appeared apg1 did not add to the model and because of the recognized subjectivity and unreliability of apg1 at very short gestations, this variable was excluded from the final model. Gestation was the dominant risk factor for ROP, with the risk of significant ROP increasing with decreasing gestation (trend, p<0.0001). A dose-response effect was also apparent in birth weight for gestation, (trend, p<0.0001) indicating the more growth restriction, the greater the risk of significant ROP. Female gender was protective.

Conclusions: The ANZNN comprises all level iii NICUS offering care to the most premature infants in both countries, hence these data are essentially population based. While gestation and gender have previously been recognized as variables significantly associated with the risk of ROP, SGA has been infrequently identified as such, most probably because earlier studies have been based on birthweight criteria. These data will be used to adjust for case-mix in future studies examining the variation in rates of significant ROP between NICUS.


Poster 23:

Should people with ROP, diabetes mellitus, or ARMD sleep with a nightlight? (The relationship of light adaptation state to retinal oxygen consumption)

Michael Gaynon

Palo Alto Medical Clinic, Palo Alto, CA
 

Purpose: To review the effect of light adaptation state on retinal oxygen consumption and to discuss the potential effect of this phenomenon on ROP, diabetes mellitus and choroidal neovascularization.

Background: The retina has a dual blood supply. Disturbance of either the retinal vascular or choriocapillaris component can potentially induce neovascularization due to excess VEGF production. Retinal neovascularization arises in the face of retinal ischemia due either to insufficiently developed retinal vessels (ROP), loss of retinal capillaries (diabetes mellitus, BRVO), or rarely due to inadequate choroidal blood supply (ocular ischemia). Choroidal neovascularization may result from a combination of mechanical factors (breaks in Bruch's membrane) and biologic factors, among them locally increased VEGF levels due to relative ischemia within the macula. Medical conditions such as atherosclerosis, pulmonary disease and sleep apnea may give rise to generalized retinal ischemia. Other factors possibly leading to macular ischemia include displacement of the neurosensory retina from the choriocapillaris by a buildup of lipofuscin, drusen and other degradation products, as well as by fluid in the case of RPE detachments and incipient CNV. Another factor might be reduced macular choroidal blood flow. It is well established in animal models that under scotopic conditions the rod photoreceptors consume more oxygen due to increased dark current activity. This can develop within 100 s after establishing dark conditions and is aborted within 100 s of turning lights back on. Avoidance of dark adaptation has been used by us for 12 years for adjunctive treatment of prethreshold ROP and has now been recommended in two papers for reducing the risk of developing diabetic retinopathy [1,2]. Two other recent studies show that choroidal blood flow in the macula is reduced under scotopic conditions, possibly due to a diversionary steal toward the rod dominant peripheral retina [3,4]. It may be that low level lighting (a nightlight) during sleep might reduce macular ischemia, thereby lowering the risk of choroidal neovascularization. Supporting evidence will be presented.

Conclusions: Dark adaptation leads to increased rod photoreceptor oxygen consumption. This, in pathologic states such as ROP and diabetes mellitus, can induce retinal ischemia, which in turn may lead to retinal neovascularization. In ARMD, choroidal blood flow may be diverted from the macula toward the periphery, which theoretically might increase the local angiogenic stimulus for choroidal neovascularization. Low level lighting may provide a safe and inexpensive method for reducing these risks.

References:
1. Arden GB. The absence of diabetic retinopathy in patients with retinitis pigmentosa: implications for pathophysiology and possible treatment. Br J Ophthalmol 2001; 85:366-70.
2. Drasdo N, Chiti Z, Owens DR, North RV. Effect of darkness on inner retinal hypoxia in diabetes. Lancet 2002; 359:2251-3.
3. Miura F, Hagiwara N, Kimura Y, Ito K, Otsubo A, Hagiwara Y, Koike T, Uehara H, Kishi S. Choroidal blood flow under light-dark adaptation. Invest Ophthalmol Vis Sci 2001; 42:S84.
4. Kergoat H, Lovasik JV, Bitton E. Reduction in choroidal blood flow in the foveal and perifoveal area during dark adaptation. ARVO Annual Meeting; 2002 May 5-10; Fort Lauderdale (FL).


Poster 24:

Posterior zone retinopathy of prematurity

Tatsuo Hirose

Schepens Eye Research Institute/Massachusetts Eye and Ear Infirmary, Boston, MA
 

Zone 1 and posterior Zone 2 disease (posterior zone) is probably the most severe type of retinopathy of prematurity. The flat extra retinal neovascularization may develop on the surface of the vascularized retina particularly on the temporal side of the fundus without going through the stages 1 and 2. This flat neovascularization may be missed. Fluorescein angiograms show profuse leakage from the flat neovascularization. Laser ablation on the avascular retina is effective to shrink the neovascularization. Retinal detachment associated with no neovascular activities with no plus disease may be dealt with closed vitrectomy with or without lensectomy or open sky vitrectomy depending upon the clinical presentations of the disease in each case. The author presents the clinical features and treatment results of stages 3 through 5 in 91 eyes of 51 patients with posterior zone ROP. Prevention of retinal detachment by laser treatment is most important for these infants to develop vision. However some eyes with totally detached retina can still be saved by vitrectomy.


Poster 25:

Association between recombinant human erythropoietin exposure and an increased risk for retinopathy of prematurity

Mark S. Brown,1 Anna E. Barón,2 Eric K. France,3 Richard F. Hamman2

1Department of Pediatrics, Presbyterian/St. Luke's Medical Center, Denver, CO; 2Department of Preventive Medicine and Biometrics, University of Colorado School of Medicine, Denver, CO; 3Department of Preventive Medicine, Kaiser Permanente, Denver, CO
 

Purpose: We hypothesized that (1) exposure to recombinant human erythropoietin (RHEPO) during the first six weeks would decrease the incidence and the severity of ROP, and (2) earlier administration of RHEPO during the first six weeks of postnatal life would decrease the incidence and the severity of ROP.

Background: Retinopathy of prematurity (ROP) is a complication of premature birth that is variable in its severity in more immature premature infants. A number of clinical characteristics, exposures, and co-morbidities have been correlated with a higher risk and severity of ROP. It has recently been suggested that exposure to recombinant human erythropoietin (RHEPO) may either increase or decrease the risk for ROP. The incidence and severity of ROP in our neonatal intensive care unit at a large referral hospital in Denver, CO changed substantially during 1995 to 1998 and created an opportunity for evaluation.

Design: Retrospective cohort study. From January 1995 through December 1998, charts of all infants <1500 g and <30 week gestation that were admitted and survived to the first eye exam at six weeks were reviewed. Primary and secondary risk factors were recorded from the first six weeks of life. 330/393 (84%) of the eligible infants had complete records and ROP exams. The risk for ROP advancement was evaluated by multivariate analysis using the continuation-ratio logistic regression model.

Results: The incidence of any ROP was 36% and of severe ROP was 9%. RHEPO exposure over the first six weeks (expressed as a total dose in international units (IU)/kg), significantly increased the adjusted risk for ROP advancement (OR=1.27 per 500 IU/kg; 95%CI: 1.04-1.55). Adjustment was made for year of birth, postnatal age of initiation of RHEPO (p=0.07), stage of ROP (p<0.001), number of transfusions (p<0.001), days of oxygen exposure (p=0.002), five minute APGAR (p=0.10), days of parenteral nutrition (p=0.09), and mg/kg of oral iron (p=0.26).

Conclusions: Contrary to our hypothesis, these findings identify an association between RHEPO exposure and an increased risk for ROP; they require further confirmation. They are consistent with the nonhematopoietic properties of erythropoietin. The use of RHEPO has been targeted to reduce transfusions in premature infants and, with or without RHEPO, reducing transfusions still remains important.


Poster 26:

Inhibition of platelet derived growth factor promotes pericyte loss and angiogenesis in retinopathy of prematurity

Jennifer L. Wilkinson-Berka,1 Sanja Babic,1 Tanyth De Gooyer,1 Alan W. Stitt,3 Kassie Jaworski,1 Leslie G. T. Ong,1 Darren J. Kelly,2 Richard E. Gilbert2

Departments of 1Physiology and 2Medicine, The University of Melbourne, Parkville, Australia; 3Department of Ophthalmology, The Queen's University of Belfast, Northern Ireland, UK
 

We investigated whether inhibition of PDGF receptor tyrosine kinase activity would affect pericyte viability, VEGF/VEGFR-2 expression and angiogenesis in a model of retinopathy of prematurity (ROP). ROP was induced in Sprague Dawley rats by exposure to 80% oxygen from postnatal (p) days 0-11 (with 3 h/day in room air), and then room air from p12-18 (angiogenesis period). Shams were neonatal rats in room air from p0-18. Sti571, a potent inhibitor of PDGF receptor tyrosine kinase, was administered from p12-18 at 50 or 100 mg/kg/day (i.p.). Electron microscopy revealed that pericytes in the inner retina of both sham and ROP rats appeared normal; however sti571 induced a selective pericyte and vascular smooth muscle degeneration. In all groups, VEGF and VEGFR-2 gene expression was located in ganglion cells, the inner nuclear layer and retinal pigment epithelium. ROP was associated with an increase in both VEGF and VEGFR-2 gene expression and blood vessel profiles in the inner retina compared to sham rats. Sti571 at both doses increased VEGF and VEGFR-2 mRNA and exacerbated angiogenesis in ROP rats, and in sham rats at 100 mg/kg/day. In conclusion, PDGF is required for pericyte viability and the subsequent prevention of VEGF/VEGFR-2 over-expression and angiogenesis in ROP.


Poster 27:

Retinal features predictive of progressive stage 4 ROP.

M. Elizabeth Hartnett, Janet R. McColm

Department of Ophthalmology, University of North Carolina, Chapel Hill, NC
 

Purpose: To determine retinal features predictive of progressive stage 4 retinopathy of prematurity (ROP) after laser treatment for threshold ROP in order to facilitate early surgical management.

Methods: 37 consecutive infants were referred either for treatment of threshold ROP or specifically for management of stage 4 or 5 ROP. All infants had sequential examination sheets available from the diagnosis of threshold disease through laser treatment and post-laser follow-up. Retinal features were abstracted from examinations made within one week of development of stage 4a ROP or two weeks after laser in eyes with regressed threshold disease. Predictive features of progressive stage 4 ROP were determined using a generalized estimating equation (gee) model to account for within-subject variability.

Results: Gee revealed that vitreous state (p=0.0039) [OR=32.6 (95%CI: 3.1-347.8)], ridge elevation >=6 clock-hours (p=0.0248) [OR=33.6 (95%CI: 1.56-722.9)], and plus disease >=2 quadrants (p=0.0490) [OR=4.95 (95%CI: 1.01-24.34)] predicted progressive retinal detachment, whereas >=2 quadrants of neovascularization (p=0.9609) did not.

Conclusions: Progressive stage 4 ROP requiring surgical intervention was predicted by the absence of clear vitreous, ridge elevation >=6 clock-hours, and >=2 quadrants of plus disease, but not by neovascularization. These results may be useful in the management of eyes after laser for threshold ROP.


Poster 28:

Two consecutive population-based studies on the incidence of ROP

Gerd Holmström, Eva Larsson

Departments of Neuroscience and Ophthalmology, Uppsala Universitet, Uppsala, Sweden
 

Purpose: Comparison of the incidence of ROP in two consecutive studies, one decade after each other, of prematurely born infants in exactly the same geographical area in Sweden. Evaluation of current national screening guidelines, including also infants with a gestational age at birth of 32 week or less.

Background: Ophthalmic screening in the neonatal period is essential for identification of infants with ROP and for initiating treatment at the right time. Because of national variations and the continuously improving neonatal care, a screening program has to be adapted to each country and must also be revised regularly.

Methods: A population-based study on the incidence of ROP in prematurely born infants with a birth weight of 1500 g or less was performed a decade ago (1988-90) in the Stockholm area of Sweden. A new study on the incidence of ROP has been performed in 1998-2000. Infants were screened from five weeks of postnatal age until the retina was entirely vascularized. The incidences of ROP in the two consecutive studies were compared. In the recent incidence study, infants with a gestational age of 32 week or less were also included, permitting us to evaluate the current screening guidelines.

Results: In the previous study (1988-90), 260 infants were included. 40% developed ROP, 20% mild ROP and 20% severe ROP, and 11% were cryo-treated (at a slightly earlier stage than the cryo ROP study). The recent study (1998-2000) included 253 infants with a similar incidence of ROP (18% mild ROP and 18% severe ROP). Laser treatment was performed in 12%. We found a change in the distribution of ROP with an increased probability of ROP in the most immature infants. Evaluation of the screening guidelines revealed that 80% of infants with a gestational age of 32 week or less were effectively screened for ROP. No infant with a gestational age of more than 31 week developed severe ROP and no infant with a gestational age of more than 29 week was treated for ROP.

Conclusions: The incidence of ROP remained the same in the two consecutive population-based studies, one decade after each other. There was a change in the distribution of ROP, with a reduced risk in the most "mature" infants and an increased risk in the most immature ones. A change of screening criteria for ROP is recommended in our population with a lowering of one week to a gestational age at birth of 31 week or less.


Poster 29:

c-Abl is required for the retinal proliferative response to hyperoxia

I. Nunes, R. Higgins, S. Goff

Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY
 

The requirement for the non-receptor tyrosine kinase c-abl in the pathogenesis of retinopathy of prematurity (ROP) was examined using the mouse model for ROP and c-abl-deficient mice. Hyperoxia-induced retinal neovascularization was observed in wild type and heterozygous mice but animals that were homozygous null for c-abl did not develop a vasoproliferative retinopathy in response to hyperoxia. Two gene products, et-1 and VEGF, have been implicated in the pathogenesis of ROP. The mRNA expression of et-1 and VEGF was assessed in mice maintained in normoxia and in hyperoxia-exposed mice. Et-1 mRNA levels were unchanged in wild type mice throughout the hyperoxia-treatment suggesting that et-1 mRNA expression is not regulated by the increased inspired oxygen. Because differential regulation of VEGF expression is observed in the mouse model of ROP and VEGF is required for the retinal neovascular response to hyperoxia, we determined if VEGF mRNA expression was aberrantly regulated in hyperoxia-treated homozgyous null mice using RNAse protection assays. A delayed decrease in VEGF mRNA was observed in hyperoxia-treated wild type animals consistent with previous reports. However, retinal VEGF expression in hyperoxia-treated homozygous null mice did not decrease and remained at normoxia control levels. These data suggest that c-abl is required for the hyperoxia-induced loss in retinal vasculature observed during phase one of the disease. To examine the role of the c-abl kinase inhibitor Gleevec in the mouse ROP model, wild type C57BL6 mice were treated with Gleevec daily when animals were exposed to hyperoxia and when they are returned to normoxia. Preliminary findings indicate that Gleevec does not protect animals from developing the retinal proliferative response to hyperoxia. Therefore, Gleevec's failure to recapitulate the c-abl null phenotype suggests that the role of c-abl in the oxygen-induced retinal proliferative response is kinase-independent.


Poster 30:

The cost-effectiveness of the Retcam in screening for retinopathy of prematurity

J. Keenan,1 J. G. Zivin,2 J. T. Flynn1

1Harkness Eye Institute, Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, NY; 2 Mailman School of Public Health, Department of Health Policy and Management, Columbia University, New York, NY
 

Purpose: Retinopathy of prematurity (ROP) is a disease of low birth weight infants that causes significant ocular morbidity. Because there is an effective treatment for ROP, it is important to screen at-risk infants for the disease. Infants are currently screened by individual ophthalmologic exams. Recently, a digital retinal camera known as the Retcam 120 has been studied as a tool for ROP screening. Because non-ophthalmologists could conduct Retcam exams, Retcam might have lower labor costs and be cost-saving. However, because the Retcam has a lower test sensitivity than ophthalmologic exam, the Retcam might result in more false negative results, rendering it a less effective test than ophthalmologic exam. It is thus unclear if a Retcam screening approach would be as cost-effective as ophthalmologic exams only. This study compares the cost effectiveness of the Retcam with the current standard of serial ophthalmologic exams.

Methods: A decision tree analysis for ROP detection and treatment was performed comparing serial ophthalmologic exams versus a Retcam approach in which only infants testing positive to at least one of two initial Retcam exams went on to receive ophthalmologic exams. Costs and effects were estimated by using data from previous clinical trials and results were reported in cost per case of blindness prevented.

Results: Ophthalmologic exam costs US$15,054 per case of blindness prevented; whereas, Retcam costs US$15,922 per case of blindness prevented. Sensitivity analyses revealed that the Retcam would become more cost-effective than ophthalmologic exam if the cost of the Retcam camera were decreased by one-fifth, or if the Retcam specificity were increased to 98% and sensitivity to 92%.

Conclusions: The ophthalmologic exam approach is more cost effective than the Retcam approach. However, at a lower Retcam camera cost and higher Retcam test specificity and sensitivity, the Retcam approach could be more cost-effective than ophthalmologic exams only.


Poster 31:

ICROP revisited

Antonio Capone, Jr.,1 Anna L. Ells,2,3 Alistair R. Fielder,4 John T. Flynn,5 Glen Gole,6 William G. Good,7 Jonathan M. Holmes,8 Gerd Holmstrom,9 Ximena Katz,10 J. Arch Mcnamara,11 Earl A. Palmer,12 Graham E. Quinn,11 Michael Shapiro,13 Michael J. Trese,14 David K. Wallace15

1Associated Retinal Consultants, Oakland University, Rochester, MI; 2Institute of Maternal & Child Health, Department of Pediatrics, University of Calgary, Calgary, Alberta; 3Pediatric Ophthamology, Alberta Children's Hospital, Calgary, Alberta; 4Department of Ophthalmology, Imperial College, London, UK; 5Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, NY; 6Department of Ophthalmology, Royal Children's Hospital, Brisbane, Queensland, Australia; 7Smith Ketterwell Eye Institute, San Francisco, CA; 8Department of Ophthalmology, Mayo Clinic College of Medicine, Rochester, MN; 9Department of Neuroscience and Ophthalmology, Uppsala Universitet, Uppsala, Sweden; 10Vicuña Departamento de Oftalmología, Clínica Las Condes, Santiago, Chile; 11Department of Ophthalmology, Wills Eye Hospital, Philadelphia, PA; 12Departments of Ophthalmology and Pediatrics, Casey Eye Institute, Portland, OR; 11Department of Ophthalmology, The Children's Hospital of Philadelphia, Philadelphia, PA; 13Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL; 14Department of Ophthalmology, Associated Retinal Consultants, Royal Oak, MI; 15Duke University Eye Center, Chapel Hill, NC
 

The international classification of retinopathy of prematurity (ICROP) was first published in 1984 and was the consensus statement of an international group particularly interested in the disease. Having a standardized classification system has facilitated the development of large multicenter clinical treatment trials and furthered our understanding of this potentially blinding disorder. With the advent of improved imaging techniques in the nursery, we may consider a more quantitative approach to some of the characteristics described in ICROP such as the presence or absence of plus disease, anterior-posterior location of the retinopathy, and disease severity. To accomplish this, an international group of pediatric ophthalmologists and retinal specialists has developed a consensus document that revises some aspects of ICROP. These include: (1) the introduction of the concept of a more virulent form of retinopathy observed in the tiniest babies (aggressive, posterior ROP, ap-ROP), (2) judging the extent of zone 1 in clinical practice, and (3) a description of an intermediate level of plus disease between normal poster pole vessels and frank plus disease (pre-plus).


Poster 32:

Treatment of grade 3+ retinopathy of prematurity with 532 nm solid state green diode laser under analgosedation

E. L. Sgattoni, C. A. Zárate, E. Alda

Megavisión: Centro Privado de Oftalmología. Bahía Blanca, Buenos Aires, Argentina
 

Purpose: To report the results of applying laser photocoagulation to the avascular retina in threshold retinopathy of prematurity using a 532 nm solid state green diode laser under analgosedation.

Methods: The authors undertook a retrospective study of 58 consecutive eyes in 29 babies satisfying the criteria of having threshold retinopathy of prematurity, which were treated by photocoagulation of the peripheral avascular retina using a 532 nm solid state green diode laser under analgosedation. With a minimum of three months follow-up examinations, results of the treatment, complications during and after the treatment and the short term anatomic outcome were evaluated.

Results: Favorable anatomic outcomes resulted in 54 eyes (93%). The only intraoperational complications that occurred were difficulty seeing the laser's aiming beam in two eyes (3.4%) and oxygen desaturations quickly resolve with temporary cessation of treatment. No postoperational complications occurred. Four eyes (6.8%) required additional photocoagulation treatment, also resulting in favorable anatomic outcomes.

Conclusions: Photocoagulation treatment of threshold retinopathy of prematurity by 532 nm solid state green diode laser under analgosedation was associated with favorable vascular development. Infants exhibited good tolerance to the treatment. No complications arose during or after treatment. Analgosedation is widely accepted in neonatology as the appropriate anesthesia for said procedure.


Poster 33:

Multipotentiality of cultured retinal angioblasts

Gerard A. Lutty, Carol Merges, Rhonda Grebe, D. Scott Mcleod

Wilmer Ophthalmological Institute, Johns Hopkins Hospital, Baltimore, MD
 

We have documented vascular precursors, angioblasts, in peripheral avascular neonatal canine retina using adenosine diphosphatase (ADPase) and alpha glycerophosphate dehydrogenase (aGPDH) enzyme histochemistry. They lack von Willebrands factor and VEGF receptor 2 (KDR) but are positive for adenosine A2a receptors (A2ar) [1]. We have described their differentiation and coalescence to form the primordial capillaries in the developing inner plexus of the retinal vasculature [2]. Ashton and coworkers hypothesized that endothelial cells and pericytes had a common mesenchymal precursor and their fate was determined by their position on the basement membrane [3]. Recent studies with hemangioblasts from marrow demonstrate that they can differentiate into either endothelial cells or pericytes depending on the growth factors they are provided [4]. The purpose of this study was to culture and characterize these vascular precursors from peripheral avascular neonatal retina and determine if they have multipotentiality. Endothelial cells were established from adult (AMEC) and two day-old central vascularized retina of dog (NMEC) by the technique of Gitlin and D'Amore [5]. Pieces of two day-old avascular peripheral retina were placed under coverslips in the same medium as canine endothelial cells until sufficient cells had explanted. Primary cultures of angioblasts were maintained in the presence of alpha-amino adipic acid to inhibit growth of muller cells. Cell lines were characterized by enzyme histochemistry for AGPDH, a marker for angioblasts [6], and immunocytochemistry with anti-von Willebrands factor (vWf, a marker for endothelial cells), antibodies for the A2ar and KDR, smooth muscle actin (in pericytes and smooth muscle cells), and GFAP (a marker for astrocytes). The cells were also evaluated for uptake of acetylated LDL, a marker for vascular endothelial cells. The effects of different substratum were also evaluated by coating plates with laminin, type 1 collagen, and fibronectin. Both endothelial cell lines were positive for vWf and uptake of acLDL while angioblasts did not take up acLDL and had reduced vWf. A2ar and AGPDH were most prominent in angioblasts and the least in AMEC, while VEGFR-2 was most prominent in AMEC and least in angioblasts. None of the cell types were positive for GFAP. To determine phenotypic expression of angioblast under different culture conditions, we evaluated expression of alpha smooth muscle actin (aSMA) and uptake of acLDL in different culture conditions. Cells were plated on one of the substrata or plastic and given bFGF, VEGF, or PDGF-bb. After seven days of culture, they were stained with alpha smooth muscle actin (aSMA) and evaluated for acLDL uptake. Culture of angioblasts on laminin with bFGF resulted in most cells taking up aLDL, while PDGF-bb on this substratum resulted in very little uptake of acLDL. Culture on fibronectin with bFGF resulted in most cells endocytosing acLDL, while culture on this substratum with PDGF-bb resulted in most cells expressing aSMA. Angioblasts cultured from peripheral vascular retina had some of the characteristics of endothelial cells but did not take up acLDL. The angioblasts appear to have multiple phenotypic potential in that they can be endothelial-like on some substratum with bFGF in the medium and pericyte-like if cultured with PDGF-bb.

References:
1. Lutty GA, McLeod DS. Retinal vascular development and oxygen-induced retinopathy: a role for adenosine. Prog Retin Eye Res 2003; 22:95-111.
2. McLeod DS, Lutty GA, Wajer SD, Flower RW. Visualization of a developing vasculature. Microvasc Res 1987; 33:257-69.
3. Ashton N. Oxygen and the growth and development of retinal vessels. In vivo and in vitro studies. The XX Francis I. Proctor Lecture. Am J Ophthalmol 1966; 62:412-35.
4. Yamashita J, Itoh H, Hirashima M, Ogawa M, Nishikawa S, Yurugi T, Naito M, Nakao K, Nishikawa S. Flk1-positive cells derived from embryonic stem cells serve as vascular progenitors. Nature 2000; 408:92-6.
5. Gitlin JD, D'Amore PA. Culture of retinal capillary cells using selective growth media. Microvasc Res 1983; 26:74-80.
6. McLeod DS, Lutty GA. Menadione-dependent alpha glycerophosphate and succinate dehydrogenases in the developing canine retina. Curr Eye Res 1995; 14:819-26.


Poster 34:

Management of laser/cryotherapy treated threshold retinopathy of prematurity (ROP) infants: A Toronto experience

Edmund Chen

Department of Ophthalmology, University of Toronto, Toronto, Ontario, Canada
 

Purpose: The management of infants with threshold ROP treated with laser versus cryotherapy was assessed. Surgical outcome for stage 4b and 5 was also analyzed.

Methods: A retrospective chart review was done for 61 infants (110 eyes) treated at the hospital for sick children (HSC) for threshold ROP with laser/cryotherapy from 1991 to 2001. The time interval between diagnosis and treatment of threshold ROP was analyzed. The surgical outcome of stage 4b and 5 (successful retinal reattachment) was examined.

Results: Laser achieved a similar regression rate (69%) compared with cryotherapy (67%). When time between diagnosis and treatment of threshold ROP exceeded 72 h, regression fell from 70% to 29%. Regression for infants followed up at HSC (67%) was similar to that for referrals from peripheral hospitals (68%). For stage 4b and stage 5 eyes, retinal reattachment after surgery was 19% (3/16 eyes).

Conclusions: Laser achieved a similar anatomical regression rate as cryotherapy in threshold ROP treatment, similar to ICROP results. Delay of treatment greater than 72 h after diagnosis may adversely affect the treatment outcome. The poor outcome (19% reattachment) after surgical procedure for retinal detachment due to ROP emphasizes the need for better prevention of threshold disease.


Poster 35:

Longitudinal study of the rod function and retinal vasculature in the rat model of ROP

Miriam Youssef, Christopher Falk, Keller Liu, Anne Fulton

Department of Ophthalmology, Children's Hospital, Harvard University, Boston, MA
 

The oxygen greedy photoreceptors have been implicated in the ROP disease process. However, the relationship of the developing rods to the retinal vasculature has not been defined. We conducted a longitudinal study of the developing rods and retinal vasculature following a within subject design. Rat models of ROP and age matched controls, aged 13 to 70 days, were the subjects of the study. Vascular parameters were derived from full-field photographic images of the retinal blood vessels. To characterize the rod photoreceptors, a parameter was calculated from the ERG a-wave responses to full-field stimuli. This noninvasive approach was used to summarize the developmental course of rod photoreceptors and retinal vasculature in ROP and control rats. Both the vasculature and rod response parameters of ROP and control subjects differed significantly. At the earliest ages the photoreceptor abnormality was relatively more severe. Some degree of photoreceptor abnormality persisted even after the vascular abnormality had resolved. Thus, the oxygen demands of the photoreceptors may be among the factors instigating the vascular abnormalities of ROP. Furthermore, residual rod cell dysfunction may be the basis for subtle visual deficits.


Poster 36:

Desmin ensheathment ratio as a predictor of vessel stability: evidence in normal development and in retinopathy of prematurity (ROP)

Matthew Page,1 Suzanne Hughes,1 Louise Baxter,1 Tom Gardiner,2 Tailoi Chan-Ling1

1Department of Anatomy, University of Sydney, Australia; 2Department of Ophthalmology & Visual Science, Queen's University Belfast, Ireland
 

Purpose: To develop a new measure of the pericyte-endothelial (P/E) ratio utilizing the intermediate filament, desmin, as an indicator of pericyte ensheathment. To provide a quantitative measure of changes in the desmin ensheathment ratio (DER) during normal retinal vascular development and during various stages of kitten ROP. To demonstrate the significant role played by pericytes and smooth muscle cells in the pathogenesis of ROP, in particular Plus Disease.

Methods: Retinal wholemounts from control kittens P1 (postnatal day 1), P3, P6, P17, P28, P32, and P45 were labeled with antibodies against desmin, smooth muscle actin (SMA) and Griffonia Simplicifolia (GS) isolectin B4. Experimental kittens were exposed at birth to 60-70% oxygen for four days and then returned to room air for 0, 3, 7, 10, 14, 23, 27, 34 and 40 days (dRA) and their retinae examined as for controls. Retinal images were captured by epifluorescence confocal microscopy. The relative occurrence of desmin and lectin labeling on confocal images yielded the DER ratio. Selected regions were also examined by electron microscopy.

Results: During normal development, desmin+ pericytes were found from birth throughout the vascular plexus including newly formed vessels, whereas differentiating SMA+ SMCs were present on radial vessels only. The DER ratio was between 0.3 and 0.6 in the immature vascular beds at the leading edge of vessel formation until P17 and reached 0.9 by P28. In the central retina where the vessels had undergone substantial selection and remodelling, the DER reached 0.9 much earlier, at P6. The hyperoxic stage of ROP resulted in the loss of intraretinal vessels with desmin+ pericytes and SMA+ SMCs ensheathment. During the hypoxic stage, endothelial cells of the neovasculature adopted an abnormal rounded morphology, desmin+ pericytes were present throughout the neovascular plexus and SMA+ SMCs were associated with the radial vessels mimicking normal development. Pre-retinal vascular membranes ensheathed with desmin+ mural cells were evident at 10, 14, 23 and 27 dRA. The pre-retinal vascular membranes and the intraretinal neovasculature observed within the first four weeks of return to room air were characterized by a DER ratio of between 0.2 and 0.5, which, during the recovery phase increased in parallel with regression of pathology, reaching 0.9 by 34 dRA. Electron microscopy revealed extensive pericyte coverage of the neovasculature in vessels with established lumena, downstream from active sprouts; the cells had plump somata rich in rough endoplasmic reticulum, but extremely attenuated processes.

Conclusions: We have introduced a new measure of the P/E ratio using desmin ensheathment in contrast to the previous method that considered the relative abundance of pericytes and endothelial cell bodies. Using this novel measure, we have shown that during normal development of the feline retina, vessel maturation was associated with an increase in the DER ratio, which reached a plateau of 0.9 in remodelled, mature vascular plexuses. Stabilization of the DER ratio by the fifth postnatal week was temporally coincident with the development of resistance to hyperoxia-induced vessel regression previously reported in the kitten. A reduced DER characterized the neovasculature of the hypoxic phase of ROP, whereas a stable DER of 0.9 emerged during the recovery phase. These observations lead us to suggest that a DER of 0.9 represents a vascular stability threshold and that the expression of desmin by pericytes is a good indicator of the functional maturation of these cells. This could serve as an effective measure of pericyte loss in disease states, such as diabetic retinopathy. Further, we have shown the significant role played by mural cells in the pathogenesis of ROP, in particular, Plus Disease.


Poster 37:

Age of oxygen exposure is an important determinant for long-term complications in mouse models of oxygen-induced proliferative retinopathy

John D. Ash

University of Oklahoma Health Sciences Center and The Dean A. Mcgee Eye Institute, Oklahoma City, OK
 

Purpose: The current rodent models of oxygen-induced proliferative retinopathy have been used with success to evaluate compounds that inhibit neovascularization. However, these models have only a transient disease state, so that after only a few days of neovascular growth, vascular tuffs in the vitreous are spontaneously and rapidly reabsorbed as the development of apparently normal retinal vasculature resumes. Unlike humans, these rodent models have very little long-term disease, which suggest that older mouse retinas have an endogenous mechanism of self-repair and protection from proliferative retinopathy. In humans the risk for developing long-term disease is highest in infants born at younger ages. Our purpose is to determine if mice exposed to oxygen at younger ages develop a more sever disease with long-term complications, and to determine the molecular mechanisms for the increased severity.

Methods: To evaluate age-specific effects of oxygen exposure on retinal vasculature, we exposed mice to 75% oxygen at three different ages. We collected eyes from mice at various times following return to room air. We then dissected and stained the retinal vasculature using GS lectin, and stained retinal astrocytes using antibodies to GFAP or s100. The stained retinas were flat mounted and analyzed by microscopy.

Results: We have observed that mice exposed to oxygen at younger ages will develop more severe disease with lasting complications, than mice exposed at ages described in current models.

Conclusions: Like humans, the ages of oxygen exposure is an important determinant for disease severity and the risk of long-term complications. We are now using the younger-exposed models to determine the molecular cause for this increased risk at younger ages and the mechanism of self protection at older ages.


Poster 38:

Peculiarities of threshold ROP in Vilnius county (Lithuania)

Rasa Bagdoniene, Rasa Sirtautiene

Department of Ophthalmology, Vilnius University Hospital, Vilnius, Lithuania
 

Purpose: To describe the main tendencies of threshold ROP in Vilnius County during eight years (1995-2002).

Background: After the crash of soviet empire the ophthalmologists from former communistic countries started to follow western diagnostic and treatment standards. Because of the lack of knowledge and equipment the earliest stages of ROP was unknown disease for soviet specialists. We just knew "retrolental fibroplasia", the end stage of ROP. Lithuania was one of the first postSoviet countries where screening and treatment for ROP was started in 1994.

Methods: Retrospective review of BW and GA of 286 infants who reached threshold ROP (according international classification of ROP) and underwent treatment in Vilnius University Hospital. All screening and treatment procedures were performed by the same two ophthalmologists (the authors of the presentation).

Results: The mean birth weight dropped over the period from 1558 g to 999 g (p<0.01). The gestational age decreased from 30.7 week to 28.1 week (p<0.01). The trend of an increasing number of more immature infants, as reflected by birth weight and gestational age distribution, is obvious in the present analysis.

Conclusions: (1) At the very beginning insufficient experience in neonatal care was the reason for ROP in "old" and "heavy" infants. (2) BW and GA is decreasing in threshold ROP. (3) With improvement of neonatal care the incidence of ROP is decreasing, but the disease still exists among the most premature infants


Poster 39:

Should fewer premature infants be screened for retinopathy of prematurity?

Rasa Sirtautiene, Rasa Bagdoniene

Department of Ophthalmology, Vilnius University Hospital, Vilnius, Lithuania
 

Purpose: To determine the possibility of restricting the inclusion criteria for screening.

Background: National guidelines of screening for ROP in Lithuania were published in 1998. The upper limits were GA of 35 week and/or BW of 2500 g.

Design: Retrospective study.

Methods: 729 infants born from January 1, 2000 till December 31, 2002 were screened for ROP by the same two ophthalmologists (the authors of the presentation).

Results: During 2000-2002 years 67 infants reached threshold ROP. All cases of threshold ROP were confined to infants with gestational ages <=33 week or birth weights <=1920 g. No ROP more than stage 1 or 2 was observed in infants with gestational ages >=34 week or birth weights >=2000 g. Restricting the inclusion criteria for screening to <=1500 g would only have reduced the total number of screenings and could have allowed us to miss seven of our threshold cases. If ROP screening is limited to infants with GA of <=28 week, 22 infants (32.8%) would not have been screened and would not have been treated in 2000-2002 years.

Conclusions: It seems appropriate to include into screening program all infants with gestational ages <=33 week and/or birth weights <=2000 g. The worldwide recommendations of screening for ROP are still not suitable enough in our county at the moment.


Poster 40:

Babies count project, the national registry for children with visual impairments, birth to three

Charles B. Boyer

American Printing House for the Blind, Louisville, KY
 

Purpose: The purpose of the Babies Count Project, the National Registry for Children with Visual Impairments, Birth to Three Years of Age, is to have a consistent process for collecting and reporting data on this special population. The American Printing House for the Blind (Louisville, KY) has been designated as the lead agency for this project.

Background: In 1995, at an International Preschool Seminar on Children with Visual Impairments, held at the Perkins School for the Blind in Watertown, MA, a decision was made that there should be a national registry. This decision grew from a discussion about how there was no consistency in collecting and reporting data across the country. A pilot project was put in place that involved nine states an a Canadian province. Dr. Deborah Hatton, a Researcher at the Frank Porter Graduate Center of the University of North Carolina (Chapel Hill, NC), volunteered to analyze the collected data. A report was submitted to the Journal of Visual Impairment and Blindness and published in June of 2001.

Methods: Participating agencies complete a survey of 43 items and submit the survey to the American Printing House for the Blind to be entered into the Babies Count database. Prior to participating in the project, staff from the American Printing House for the Blind provides training to insure the process is understood. Dr. Hatton will analyze the data and prepare a report for publication by June of 2004. One thousand surveys have been received from 11 states since January of 2001. Eight new states received training between June of 2002 and August of 2003. Fifteen states will receive training over the next twelve months.

Results: Seven hundred surveys were submitted for the pilot project, and one thousand surveys have been received since the American Printing House for the Blind accepted responsibility for the project beginning January 1, 2001. The one thousand surveys have not been entered in the new database, but a review of the surveys as they were received by the American Printing House for the Blind provided some interesting information. When combining the 700 surveys from the pilot project and the 1,000 since January 1, 2001, there seems to be consistency in the following: (1) most prevalent eye conditions: CVI-23%, ROP-17%, ONH-8%; (2) amount of vision: legally blind-53%, not legally blind-16%, Unknown-31%; (3) multiple disability risk status: VI only 45%, VIMD 33%, VIDD 23%; (4) health conditions: seizures-27%, respiratory problems-18%; and (5) referral for services sources: medical 50%, early intervention 38%. NOTE: The analysis of the data is preliminary, and a final report will be out in 2004.

Conclusions: It is the desire of the professionals in the field of blindness that there be a collaborative effort with the medical professionals to insure that children with vision problems, and those with potential vision problems, be identified and referred as early as possible to provide them the greatest opportunities to develop, grow, and learn at the same pace as their sighted peers.


Lutty, Mol Vis 2006; 12:532-580 <http://www.molvis.org/molvis/v12/a63/>
©2006 Molecular Vision <http://www.molvis.org/molvis/>
ISSN 1090-0535