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Airton L. Kronbauer, Paulo Schor, Wallace Chamon, Luciana d. Matos, Luis A. Carvalho; On a New Visual Evaluation Method using Psychophysical Tests and the Candela Unit. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1896.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a psychophysical test for easy and accurate visual evaluation using the international system of units (A), and compare the results between standardized objective and subjective methods (B).
(A) Based on concept of minimum visible threshold, a psychophysical test was developed using a calibrated digital device that is based on the principle of photometry with photodiodes. (B1) Subjective measurements of visual acuity were taken, in normal individuals, using ETDRS (logMar) standard charts and compared to the proposed logCandela method (n=126 measurements). (B2) Objective (total wavefront RMS) and subjective (ETDRS) measurements were taken between patients in pre and postoperative corneal refractive surgery and compared to the logCandela (n=48 measurements).
Correlation between ETDRS and logCandela was 84,14%, calculated by exponential correlation of Pearson and t test (p<0,001). The variability of measurements in examined volunteers and examiners was narrower logCandela method than ETDRS. Pearson linear correlation between objective (total wavefront RMS) and subjective measurements (logCandela and ETDRS) was 88% and 96%, respectively. Wavefront maps, PSF plots, total wavefront RMS, ETDRS and logCandela improved after corneal refractive surgery.
In normal eyes, there is a positive correlation between the subjective visual acuity tests performed (ETDRS and logCandela) as well as between these tests and objective measurements (total wavefront RMS). This psychophysical test of luminous intensity with logCandela unit may be used in the daily practice for visual evaluation.
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