Correlation of visual acuity and contrast sensitivity in visually disabled patients of moderate to severe diabetic retinopathy

Purpose: Aims of this study is to characterise the visual disability of patients of moderate to severe diabetic retinopathy in terms of logarithm of minimum angle of resolution (LogMAR) visual acuity and contrast sensitivity. Methods: A total of 30 eyes with moderate to severe diabetic retinopathy having low vision (WHO Criteria) with predefined inclusion and exclusion criteria were included as cases and 40 eyes with normal or near normal visual status correctable by refraction were included as control in the study. The visual acuity and contrast sensitivity were noted and analysed. Results: The best corrected visual acuity (BCVA) of all eyes in control group is less than 0.5 LogMAR units. Among cases, 29(96.7%) eyes have BCVA in the range of 0.5 to 1.0 LogMAR units and 1(3.3%) eye has BCVA in the range of 1.0 to 1.3 LogMAR units, satisfying the inclusion criteria significantly (p value < 0.001). In case group, direct correlation of association is observed between uncorrected visual acuity and best corrected visual acuity (r = 0.69), near visual acuity (r = 0.49), best corrected near visual acuity (r = 0.64) and inverse correlation of association with contrast sensitivity (r = -0.65) which are statistically significant (p value <0.05). Conclusions: In patients of diabetic retinopathy with visual impairment, irrespective of varying pathology of visual impairment, there is a negative correlation between contrast sensitivity and visual acuity in logMAR units. The logMAR visual acuity and contrast sensitivity is a better tool than vision assessment by snellen chart for evaluation, monitoring and prescription of low vision devices in subjects with visual impairment.