Longitudinal comparison of visual acuity as measured by the ETDRS chart and by the potential acuity meter in eyes with macular edema, and its relationship with retinal thickness and sensitivity.

Abstract

To evaluate the relationship between visual acuity as measured by the Early Treatment Diabetic Retinopathy Study (ETDRS) chart and by the potential acuity meter (PAM) with retinal thickness and sensitivity measured by a combined microperimetry/optical coherence tomography system (OCT). Forty-four patients with macular edema (ME) were included in a prospective observational study. Visual acuity (VA) was assessed using the ETDRS chart (with best correction) as well as by the PAM. Retinal thickness and sensitivity was measured by an automatic fundus perimetry/tomography system. Best-corrected VA using the ETDRS chart ranged from 20/20 to 20/400 (median: 20/50). VA measured by the PAM without correction ranged from 20/20 to 20/400 (median: 20/40). The mean retinal thickness was 369.57 μm (s.d.: 140.28 μm) on spectral domain-OCT and the mean retinal sensitivity was 8.12 decibels (dB) (s.d.: 5.78 dB). The mean LogMAR value using the ETDRS chart was 0.43, whereas it was 0.38 using the PAM (P-value: 0.009). VA values measured by the PAM were statistically significantly better than those measured by the ETDRS chart in eyes with ME secondary to various retinal vascular and uveitic diseases. VA measured by the PAM may be a more sensitive predictor of macular function than that obtained by ETDRS testing in eyes with ME.