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R. Krishnamurthy, S. Meenakshi; Assessment of the Accuracy of Lea Symbols as a Vision Testing Tool in Amblyopes . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2584.
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Purpose: Young amblyopes require constant follow–up, usually via the measurement of visual acuity. As the ethnic and linguistic diversity of patient populations grows in the U.S., it is necessary to appropriately identify and follow non–English speaking amblyopes. This requires an accurate, reliable, standardized vision testing tool which is devoid of cultural bias. Lea symbols offer an universal method of vision testing for young preliterate or illiterate children, especially for children unfamiliar with the English alphabet. This study seeks to determine if Lea symbol acuity is comparable to Snellen acuity in its ability to detect the interocular difference of amblyopes. Methods: 14 Indian unilateral amblyopic subjects (ages 4 to 72 years, literate in English alphabet as a second language, with fewer than 2 visits to the hospital to avoid Snellen learning curve bias) had vision tested using both Lea symbols and Snellen acuity, the sequence of which was determined by a randomization scheme. Subjects who had ophthalmic pathology on fundus examination, did not possess the best optical correction in their glasses, or had vision worse than 6/60 in the amblyopic eye were excluded. The amblyopic eye was tested first, followed by the normal fellow eye. Data was calculated using Log MAR conversions of acuity. The relationship between Snellen and Lea symbol acuity was compared by performing correlation analysis of the normal and fellow eye, as well as the interocular difference as determined by each acuity measure. Results: Visual acuity testing showed that Snellen and Lea symbols were well correlated in assessing vision in the amblyopic eye, fellow eye, as well as for interocular difference. (r for amblyopic eye 0.874, r=0.957 for fellow eye and r=0.923 for interocular difference). The mean acuity measurements for the amblyopic eye were as follows: 0.564 + 0.223 for Lea symbols and 0.554 + 0.191 for Snellen acuity. The mean values for the interocular difference calculated by Lea symbols was 0.41 and 0.38 for Snellen acuity. Conclusions: Preliminary data indicates that Lea symbols are well correlated with Snellen testing in assessing vision in amblyopic and normal fellow eyes. In addition, testing with Lea symbols was able to detect the interocular difference of amblyopes, which is essential in guiding treatment decisions. Thus, Lea symbols offer an attractive alternative to assessing and following preliterate or English illiterate amblyopic patients.
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