Quantitative Phenotyping of Chromatic Dysfunction in Best Macular Dystrophy

Objectives: To quantify chromatic dysfunction in Best disease to reassess the classic categorization of macular chromaticdamageandtoinvestigatepsychophysicaland clinical correlations. Methods: Color-contrast discrimination was measured using 2 different psychophysical strategies in agematched control (n=41) and patient (n=34) eyes. The first strategy measured performance along 3 main confusionlines(testingconefunction),andthesecondevaluated discrimination ellipses (modified Cambridge Color Test). The main outcome measures were chromatic discriminationvariables(confusionlinelength,ellipselength, angle, and axis ratio) and visual acuity (VA). Results: Significant loss of performance was seen in all color axes in our patients, and it increased monotonicallywithstaging,becomingsignificantinFishmanstages 2 and 3. The classically assumed preferential type I redgreen deficit was true only for stage 4. Substantial chromatic dysfunction occurred even with relatively preserved VA despite that negative correlations between all testvariablesandVAreachedstatisticalsignificance.Partial correlation analysis showed that protan/deutan loss was related to VA independent of tritan loss. Statisticallysignificantpositivecorrelationswerealsofoundbetween lesion size and chromatic dysfunction. Conclusions: Chromatic discrimination is often impaired in Best disease, even when VA is still spared. Our quantitativepsychophysicalapproachshowsthattheclassiccategorizationasatypeIred-greendeficitisvalidonly for disease stage 4.