Abstract
Purpose: :
To compare the results of visual acuity (VA) measurement between Snellen and the Early Treatment Diabetic Retinopathy Study (ETDRS) charts in patients with and without macular disorders.
Methods: :
This is a prospective single masked study. Patients with and without macular disease were evaluated by a single examiner. The same room and same room illumination were used to test all patients. Patients had their best corrected visual acuity (BCVA) measured with both charts and at the same day by the same ophthalmologist who was masked to the eye condition. Patients were divided into two groups: Group I with no macular disease and Group 2 with macular disease. For the ETDRS test we used chart 1 to test the right eye and chart 2 to test the left eye. Snellen values were converted into logMAR for statistical analysis. Main exclusion criterium included VA lower than 20/200.
Results: :
Sixty eyes of 30 patients were included. Thirty eyes were in Group 1 and 30 in Group 2. Results of group 1: seven were male and 8 were female, mean age was 26 years old (range: 23 to 79 years old) and the mean ETDRS VA was 0.28 (range: 0.0 to 0.7) and the mean Snellen VA was 0.29 (range: 0.0 to 0.7) . There was no significant statistical difference between the results (right eye: p = 0.054 and left eye: p=0.164). Seven patients had cataract and the other eight had just refractional disorders.Results of Group 2: eleven were female and four were male. The mean age was 58.7 years old (range: 48 to 73 years old). Twelve patients had diabetic macular edema, one patient had myopic choroidal neovascular membrane and two had macular epiretinal membrane. The mean VA was 0.61 (0.0 to 1.0) in ETDRS and 0.62 (0.0 to 1.0) in Snellen charts. The results showed no significant statistical difference (right eye: p= 0.182 and left eye: p=0.783).
Conclusions: :
In this study the BCVA measured by the Snellen and the ETDRS charts were comparable for both patients with and without macular disease. Since the Snellen chart is commonly used in the most part of the offices all over the world and the ETDRS chart is widely used in clinical trials one can assume equivalence between the clinical trials VA results with the every-day VA measurement.
Keywords: visual acuity • macula/fovea • refraction