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A.V. Sailoganathan, J. Siderov, E. Osuobeni; Letter Legibility of Hindi and Sloan Optotypes . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2782.
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Purpose: To investigate relative letter legibility of Hindi & Sloan Optotypes. Methods: In experiment 1, the influence of font type on letter legibility was studied on 8 subjects optically defocused using a +1.00 DS lens in front of one eye. Two Hindi font types used in widely read Hindi language newspapers and magazines were selected. Legibility was determined according to the method of Strong & Woo (1985). In experiment 2, a single Hindi font (selected from expt.1) was used to investigate relative letter legibility in 9 subjects who were optically defocused with a +1.00DS, +2.00D cyl, axis 180 & 90. Ten Sloan letters were selected and optically defocused on 20 subjects. The Hindi letters were modified to fit into a 5x5-grid using Coral draw and presented on a standard PC monitor at high contrast using Powerpoint. The method of Strong and Woo (1985) was used to determine relative letter legibility. Results: The results of experiment 1 showed no effect of Hindi font type on letter legibility (ANOVA, p>0.05). The results of experiment 2 were analysed as follows. ANOVA including post hoc analysis showed significant differences in legibility between individual letters under all three blur conditions (p<0.05) for both Hindi & Sloan Optotypes. In order to select optotypes with minimal relative legibility difference we plotted the percentage difference in relative legibility under cylinder blur (axes 180 & 90) against the legibility under spherical blur. We selected 14 letters in Hindi and 9 Sloan letters on the basis that the difference in relative legibility for each cyl condition was no more than 10% of the spherical blur condition value. Conclusions: Relative legibility of Hindi letters was determined resulting in the selection of 14 letters. These letters will form the basis of a new, standardised vision chart in Hindi.
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