Residual colour detection abilities in age-related macular degeneration

To quantify residual abilities to identify a target's colour in cases with age-related macular degeneration (AMD).

Subjects with AMD with best corrected visual acuity (BCVA) of 20/50 to 20/400 in the better eye (test eye) and age older than 55 years were recruited. A separate matching control group was recruited with subjects with BCVA of 20/40 or better. Each subject was presented sequentially with square-shaped colour targets corresponding in size to optotype sizes used in standard Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity testing protocols, all against a white background. Four major colour hues were selected for testing: blue, yellow, green, and red. The same subjects were tested with standard ETDRS targets (black on white), and results served as control group references. The primary outcome measure selected for analysis was the minimum angle of resolution (MAR) required to correctly identify the hue presented.

Forty study subjects (14 males and 26 females) aged 55 to 95 years (mean 79.45 years, SD 8.82) were recruited. Thirty similar subjects were recruited for a control group. Red on white estimates were better than for other colours and related best to standard black on white ETDRS estimates (20/121 vs 20/132, respectively). Also, red on white estimates seem not to be affected by age. Estimates for colour detection for the control group were not different among colours tested and were not affected by age.

Ranking abilities according to the MAR required to identify a hue can serve as a quantifying measure for residual colour vision. Our findings reflect functional abilities rather than psychophysical measurements.