Estimating visual acuity by character counting using the Snellen visual acuity chart
نویسندگان
چکیده
منابع مشابه
[Snellen visual acuity evaluation].
PURPOSE To evaluate the visual acuity (VA) measurement by Snellen chart at three main Ophthalmology centers in Curitiba, compare these measurements with a computerized method for calibrating VA and also with the standard theory developed by Hermann Snellen. METHODS Descriptive study including 15 Ophthalmology clinics and a computerized method to measure the VA. Using a tape measure and a cali...
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A Bayesian model of Snellen visual acuity (VA) has been developed that, as far as we know, is the first one that includes the three main stages of VA: (1) optical degradations, (2) neural image representation and contrast thresholding, and (3) character recognition. The retinal image of a Snellen test chart is obtained from experimental wave-aberration data. Then a subband image decomposition w...
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SIR, -I read with great interest the paper by Wong and Kaye on a suggested chart for visual acuity screening.' However, I was surprised to find that they recommended widespread clinical use of this chart without any clinical data to confirm its suitability. The statistical argument they use is compelling, but surely a comparison with other methods of acuity testing should be undertaken to confi...
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The effect of artificially induced image defocusing on visual acuities (VAs) measured by spatial frequency sweep pattern reversal visual evoked response (SPVER) and Snellen measurement was studied in six normal subjects. The steady-state SPVER was recorded using vertical gratings of 10 different spatial frequencies ranging from 0.52 to 30.36 c/deg. The SPVER acuity was compared with Snellen acu...
متن کاملOn the statistical reliability of letter-chart visual acuity measurements.
PURPOSE To determine boundary values of test-retest reliability and sensitivity to acuity change that are unlikely to be exceeded in any clinical situation, for a popular visual acuity chart (Lighthouse/ETDRS) with three scoring methods; to discuss general methodological issues associated with statistical accuracy of optotype chart testing; and to link measures of test reliability to measures o...
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ژورنال
عنوان ژورنال: Eye
سال: 2004
ISSN: 0950-222X,1476-5454
DOI: 10.1038/sj.eye.6701583