Purchase this article with an account.
P. Tzatzala, S. Plainis, H.S. Ginis, M.K. Tsilimbaris; Evaluation of a Modified ETDRS Visual Acuity Chart Which Contains a Set of Sloan Roman Letters Used in All European Alphabets . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5360.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The logMAR visual acuity charts developed for use in the Early Treatment Diabetic Retinopathy Study (ETDRS) contain ten Sloan letters, with nearly equivalent probability of correct identification and ultimate homogeneity of difficulty per line (Ferris III et al., 1982, 1993). However, the set is composed of Roman letters, which are not used in Greek, Cyrillic and Central European alphabet. In this study we evaluate a modified logMAR chart, which contains Roman letters used in all European alphabets.
In the modified logMAR / ETDRS chart, the Roman letters C, D, R, V, S and Z were substituted with E, P, B, Y, A and T, respectively. The chart was evaluated using two procedures. First, visual acuity of 80 subjects (160 eyes) with normal vision (spherical equivalent ranged between +3.00 to –3.00D) was assessed using a set of three standard ETDRS logMAR charts and another set of three modified charts. Second, psychometric functions for the identification of the twelve letters were measured as a function of logMAR at maximum letter contrast. Letters were projected on a Sony GDM F–520 CRT monitor (background luminance of 60 cd/m2, frame rate of 120 Hz) by means of a VSG2/5 stimulus generator card, presented at a distance of 3m. Data were obtained from four subjects with normal vision.
No statistically significant difference was found in the value of visual acuity assessed with the standard and the modified ETDRS charts. Moreover, estimates of identification threshold in logMAR, derived from best–fits of psychometric functions, showed relatively little inter–letter variability in threshold logMAR for high–contrast letters.
The overall pattern of results suggests that the modified logMAR ETDRS chart forms an alternative optotype for assessing visual acuity, offering the advantage of containing letters recognisable by all European citizens.
This PDF is available to Subscribers Only