Correlation of Colour Contrast Sensitivity With Stage of Age Related Macular Degeneration

Abstract

Abstract: : Purpose: Visual function as determined by visual acuity in Age Related Macular Degeneration (AMD) is variable. Previous studies evaluating colour contrast sensitivity in AMD have suggested that the tritan thresholds may be a sensitive marker of disease progression. This study was undertaken to evaluate colour visual deficits in patients with a range of AMD grades and to identify if there was a relationship in the extent of the deficit when compared to the stage of the disease. Methods: In a prospective study, 115 eyes of 70 patients (mean age 74 years, standard deviation 8 years) with macular drusen or late AMD as defined by the Rotterdam modified international classification system were assessed using the ChromaTest©, a computerised psychophysical test of colour thresholds along protan and tritan confusion axes using optotypes. Patients with ocular co–morbidity other than AMD were excluded. Colour digital fundal images (Topcon®) centred on the fovea were used to grade the stage of the disease by an independent grader. Results: Visual acuity was 6/18 or better in all tested eyes. The colour contrast thresholds were significantly correlated with AMD grade for both protan and tritan axes using 1.5 degree optotypes (Spearman’s rank, p=0.01) and 6.5 degree optotypes (Spearman’s rank, p=0.05). Conclusions: This study demonstrates that colour contrast thresholds for protan and tritan axes correlate significantly with AMD grades ranging from early to late stage disease using both smaller and larger optotypes. Differences in colour function especially involving the tritan thresholds may therefore be useful in monitoring disease progression in patients when fundal features are stable.

Keywords: color vision • age-related macular degeneration • drusen