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Claire Iscar, Veronique Promelle, Emilie Haritchabalet, Solange Milazzo; Comparison of two angular eye charts for assessment of visual acuity in amblyopia : Thibaudet and Snellen tests. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3092.
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© ARVO (1962-2015); The Authors (2016-present)
Visual acuity is dependent on the eye discrimination power. Among existing tests, Thibaudet and Snellen tests are two angular eye charts, validated for distance visual acuity evaluation. Amblyopic patients suffer from a weakening of their visual acuity and largely from a perturbation of their overall visual experience. The main objective of this study is to determine if Thibaudet and Snellen are equivalent in evaluating visual acuity in those amblyopic patients.
All amblyopic patients under 40 years who consulted at Amiens University Hospital between August 2014 and March 2015 were included prospectively. They presented a difference between two eyes of two lines or more on morphoscopic projected tests. The minimum age depended on the feasibility of the tests. The best corrected visual acuity (BCVA) was determined for each eye in a randomly chosen order, using a Thibaudet test and a Snellen test. The evaluation began with the same test for both eyes, under standardized conditions of room management, light and the presenting distance. For each included eye, the BCVA obtained with one test was compared to the BCVA obtained with the other
The study included 140 eyes of 70 patients, from 2 years and 11 months to 37 years and 6 months. 34 were female. 20% had bilateral amblyopia. 16% suffered of organic amblyopia and 53% of functional amblyopia, while 31% had a mixed amblyopia. For a presenting distance of less than 5 meters, the mean BCVA was not different between two tests (0.27 lines weaker with Thibaudet compared to Snellen test). Conversely, for a presenting distance of more than 5 meters, the mean BCVA was 4.1 lines better with Thibaudet compared to Snellen test
The Thibaudet test seems to overestimate visual acuity compared to Snellen Test. The presentation distance is a major factor of reliability of those tests in the assessment of visual acuity. With a mean variability of 4 lines in the measured BCVA, Thibaudet test might ignore a mild to moderate relative amblyopia, so it should not be used to detect amblyopia. This easy-to-use test can prove useful in evaluation of children while in addition to others available tests.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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