Outcome Measures: For both the CCT and LvCCT, an overall quantitative measure of color vision will be obtained from the calculation of achromatic area. The sensitivity of CCT and LvCCT will be examined by comparing achromatic area for IRD participants with varying levels of phenotype severity defined by measures of retinal structure and function. Secondary outcomes for this study include: 1) evaluation of sensitivity of the CCT and LvCCT to disease severity,