Figure 2. Grading scale for β-galactosidase expression

Grading scale (0 to 5) used to evaluate the extent of β-galactosidase expression in rat eye cups. Representative eye cups are shown from the present study. Grade 5 is expression indicating confluent transduction of the entire retinal surface area. Grade 4 is expression in large confluent areas of at least half of retinal surface area. Grade 3 is expression in confluent areas with less than half the retinal surface area. Grade 2 is expression in large areas of non-confluent transduced cells. Grade 1 is expression in isolated, discrete transduced cells. Grade 0 has no detectable β-galactosidase activity.