Figure 4. IOP and TID lack strong correlations. The transillumination defect (TID) does not influence intraocular pressure (IOP) in BXD murine strains when they are stratified based on the Tyrp1/Gpnmb genotype. Some strains that are wild-type at Tyrp1 and Gpnmb (green symbols) developed high IOP but showed negligible TID. However, some that are mutant at Tyrp1 and Gpnmb (red symbols) had low IOP values and high grades of TID, thus demonstrating that TID does not directly influence IOP. The n values ranged from 4 to 13 mice per BXD strain.