Impact of colour in the assessment of potential visual acuity in patients with age-related macular degeneration

Objective: To compare chromatic and achromatic potential visual acuity (PVA) in patients with bilateral low vision caused by age-related macular degeneration (AMD). Design: Prospective, nonrandomized, observational case series. Participants: Fifty-five patients, representing a consecutive series of patients all presenting with bilateral AMD. Methods: Best-corrected visual acuity of each eye was measured using an Early Treatment in Diabetic Retinopathy Study (ETDRS) chart with appropriate near correction. Included were cases with visual acuity of 0.4 logMAR (20/50) or worse in both eyes. Achromatic and chromatic PVA were measured in each eye using white on black and red on yellow flooding E charts at 50 cm in controlled lighting conditions. Results: One hundred and seven eyes from 55 patients were included in the analysis. Mean achromatic and chromatic PVA were 0.69 +/- 0.26 and 0.65 +/- 0.22 logMAR, respectively. Overall, patients had a significantly higher chromatic than achromatic PVA, with a median difference of 0.1 logMAR (p < 0.05). Patients with ETDRS visual acuity worse than 0.9 logMAR also had a significantly higher chromatic than achromatic PVA, with a median difference of 0.1 logMAR (p < 0.05). Patients with ETDRS visual acuity between 0.4 and 0.9 logMAR had a trend toward a higher chromatic than achromatic visual acuity that was not significant, with a median difference of 0.1 logMAR (p = 0.8539). Conclusions: Patients with low vision caused by AMD can discern smaller targets when a red on yellow colour scheme is used than when using achromatic white on black charts.