Color Vision as a Measure for Inherited Retinal Diseases

Objective: The aims of this study are to 1) examine the sensitivity of the Cambridge Color Test (CCT) and the low vision CCT (LvCCT) to the severity of retinal disease in inherited retinal degeneration (IRD) by comparing color vision status with changes in photoreceptor structure and function, 2) examine the effects of eccentric fixation and reduction in visual acuity on color discrimination thresholds obtained with the CCT and LvCCT, and 3) establish normal ranges for the CCT and the LvCCT and determine the intra-session and inter-session variabilities for these tests.

Study Population: Up to 59 healthy volunteers and 144 IRD participants age 5 or older will be enrolled in this study.

Design: This study will be comprised of three related projects. For Aim 1, color discrimination thresholds (CCT and LvCCT) and assessments of retinal structure (imaging) and function (perimetry/microperimetry and electroretinogram) will be measured in 144 IRD participants with varying retinal phenotypes and visual acuities. IRD participants will be divided into four major categories: 1) cone & cone-rod dystrophies, 2) rod-cone dystrophies, 3) inherited maculopathies, and 4) inherited retinal dysfunction syndromes. The fourth category will be used for IRDs that do not match the description for categories 1-3 (i.e., x-linked retinoschisis, congenital stationary night blindness). Degree of severity of retinal dysfunction in IRD participants will be determined relative to the normal ranges obtained from the healthy volunteers (see Aim 3a below). For Aim 2 color discrimination thresholds (CCT and LvCCT) will be measured in one eye from 12 healthy volunteers in order to examine the effects of eccentric fixation and reduced visual acuity on color thresholds independent of retinal pathology. Between one and three study visits will be required for this aim. Aim 3 will be comprised of two parts. For Aim 3a, color thresholds will be collected from both eyes (for intraocular variability) of 35 healthy volunteers age 5 or older. For Aim 3B, color discrimination thresholds (CCT and LvCCT) will measured from 12 healthy volunteers twice in one session and then again at a second visit occurring within two months of the initial visit to determine intra-session and inter-session variability.

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,

• evaluation of the effects of decreased visual acuity and eccentricity on color discrimination thresholds (CCT and LvCCT), 3) establishment of the normal range of color discrimination thresholds (CCT and LvCCT) as a function of age, and 4) determination of intra- and inter-session variabilities of the two tests.

• INCLUSION CRITERIA:

• Participants must be 5 years of age or older.
• Participant (or legal guardian) must understand and sign the protocol s informed consent document.
• Participant must be able to cooperate with the testing required for this study.
• Participant s eyes must have clarity of ocular media and degree of pupil dilation sufficient to permit adequate fundus photography.
• For IRD Participants only:

• Participant must have IRD, defined as evidence of retinal rod- and cone-mediated

dysfunction and degeneration established by standard clinical methods including field tests, ERG, and imaging.

• Participant must have a measurable visual acuity.
• For Healthy Volunteers only:

• Participant must have visual acuity of 20/20 or better.

Exclusion criteria

• Participant is taking medications known to alter color vision, such as hydroxychloroquine (Plaquenil ), sildenafil (Viagra ), ethambutol, chloroquine amiodarone, and pamidronate disodium.
• Participant has another ocular disease that may confound the study results, such as diabetic retinopathy, vascular occlusions, retinopathy related to drug toxicity, optic neuropathy, or central serous chorioretinopathy.