Posters

Standard ETDRS chart versus Topcon LCD screen for logMAR visual acuity measurements

Poster Details

First Author: L.Wielders THE NETHERLANDS

Co Author(s):    J. Schouten   F. van den Biggelaar   B. Winkens   R. Nuijts     

Abstract Details

Purpose:

Logarithm of the Minimum Angle of Resolution (logMAR) visual acuity charts have become the standard for visual acuity (VA) measurements in clinical research. Standardisation within and among clinical trials is of great importance, because the success of ophthalmic interventions is often represented as improvement in VA. It is well known that several factors, including luminance, contrast and test distance may influence VA. The Early Treatment Diabetic Retinopathy Study (ETDRS) protocol has been the gold standard for logMAR VA measurements for many years. However, several other charts, including the ETDRS chart displayed on Topcon LCD screens, have been designed to measure logMAR VA. The aim of this study was to compare VA measurements using a standard ETDRS chart and Topcon LCD screen.

Setting:

Hundred eyes of 50 patients with cataract in at least one eye were included in the study.

Methods:

VA was measured using a standard ETDRS chart and ETDRS illuminator cabinet and a Topcon LCD screen in all patients. The sequence of both tests was random to control for learning effects and fatigue. Patients were asked to read all letters starting from the top of the chart. Testing stopped if less than three letters on one line were identified correctly.

Results:

Mean VA was 0.22±0.21 and 0.21±0.20 logMAR using a standard ETDRS chart and 0.20±0.17 and 0.18±0.17 logMAR using the Topcon LCD screen (p = 0.14 and p = 0.04) for right and left eyes respectively. Correlation between VA measurements was 0.88 for right eyes and 0.86 for left eyes. There was no tendency for scores on one test to be higher as compared to the other test. Bland-Altman plots were constructed to assess the concordance of both measurements. Thirty-three percent of all eyes showed a difference of ≥0.1 logMAR between both measurements. This difference was moderately correlated to VA using a standard ETDRS chart (ρ 0.58, p = 0.00 and ρ 0.52, p = 0.00 for right and left eyes respectively), but not correlated to VA using an LCD screen, age or type and grade of cataract.

Conclusions:

This study found a clinically and statistically significant difference in logMAR VA measured using a standard ETDRS chart and Topcon LCD screen. FINANCIAL INTEREST: NONE