Purchase this article with an account.
Linda Tsai, Eugenia Thomas, Janice Tarrant, Stan Bentow, Sanjeev Kasthurirangan; A Comparative Clinical Evaluation of Two Visual Acuity Testing Systems: ETDRS vs. FrACT. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3890.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Visual acuity (VA) results with physical Early Treatment of Diabetic Retinopathy Study (ETDRS) letter charts are heavily dependent upon the test administrator ability (i.e., better threshold VA with persistent encouragement, accurate recording of correctly read letters). In addition, the risk of subject memorization with physical charts requires the administrator to change charts frequently. The impact of such factors may be reduced with the use of a VA software program that automates testing by allowing the test subject to view randomized optotypes in a staircase size presentation and respond with direct input to the software program, which then determines threshold acuity. This clinical study evaluated results with both test systems.
A total of 25 subjects were evaluated for distance-corrected visual acuity at far, intermediate and near and distance defocus testing from +2.00 diopters (D) to -4.00 D, in 0.5 D increments. Each subject was tested monocularly with a retroilluminated ETDRS chart and a computer-based vision testing software, the Freiburg Visual Acuity and Contrast Test (FrACT). All results were obtained in logMAR format, and analyses were conducted in paired comparisons between the two testing systems.
Across all test distances, visual acuity results with FrACT were found to be within 0.05 logMAR of ETDRS chart results. Generally, a difference less than 0.1 logMAR (1 line of Snellen acuity) was found in 80% (20/25) of subjects. ETDRS visual acuities were frequently better than that with FrACT; there was a 0.1 logMAR difference at far and 0.06 logMAR differences at both intermediate and near. With defocus testing, there was a mean difference of 0.05 logMAR across the defocus range, with the greatest differences between -2.00 and -4.00 D (mean of 0.08 logMAR). The mean best-corrected distance VA (BCDVA) was slightly better than the mean VA with the manifest refraction (0.00 D defocus) in the defocus sequence with both ETDRS (0.02 logMAR) and FrACT (0.03 logMAR).<br />
VA test results with the FrACT system were found to be slightly worse than that with the ETDRS letter charts. However, the benefits of automated administration of VA testing with the FrACT system merit further evaluation of test factors that may affect results.
This PDF is available to Subscribers Only