WHY DO RETINITIS PIGMENTOSA PATIENTS LOSE THEIR BLUE COLOR VISION FIRST?

POSTER PRESENTATIONS

Objective. We explored whether history of vision loss or current visual function status may predict which retinitis pigmentosa (RP) patients are susceptible to loss of short wavelength cones (i.e., s-cones for blue-violet colors). Background. Previous studies reported that some RP patients initially lose s-cones prior to longer wavelength cone function, but it is unknown how this relates to scotopic night vision loss. Methods. At two visits within a month, 22 RP subjects with visual acuity (VA) better than 20/400 completed the PC-based Innova Rabin Cone Contrast Test (CCT) and AdaptDx dark-adaptation in each eye. Results. Of 22 RP patients tested, 15 (68%) had measurable CCT results and they had VA better than 0.5 logMAR (20/60). All of the subjects who did not have any measurable rod function with the AdaptDx (n=10) had the greatest CCT loss for scone sensitivity (mean score of 23 across subjects) compared to l- and m-cones (mean scores 55 and 51, respectively), while those with rod function (n=5) had either normal s-cone function or relatively equal reductions for all three cones (mean scores 87, 88 and 84 for l-, m- and s-cones, respectively). Statistically significant predictors of reduced s-cone sensitivity were reduced VA and absence of current rod function (p < 0.01). Conclusion. In the absence of functional rods, there was a greater loss of s-cone sensitivity than l- and m-cones in RP patients. Future clinical trials should measure the responsiveness of specific cone types to therapeutic approaches to help yield further valuable insight into the mechanisms involved in s-cone loss. Grants. NIH funding to AKB: R21 award EY023720