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I de la Fuente, JG Vizmanos, BM Matesanz, JA Aparicio; Influence of Surround Illumination on Contrast Sensitivity Measurements . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4709.
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Purpose: Contrast sensitivity measurements have acquired a great importance in clinical practice. Results depend on many parameters such as the characteristics of the test, the psychophysical procedure or the illuminating variables. The studies concerning the latter aspect mainly deal with the mean luminance of the test chart but the influence related to the surround luminance appears to be less investigated. The aim of this work is to determine whether there is a significative difference between two differently illuminated surrounds. Methods: We have measured contrast sensitivity making use of a letter test chart of a mean luminance of 200 cd/m2 and with two different surround luminance conditions: 150 cd/m2 and 0.8 cd/m2. The test was performed by 64 subjects with normal vision and ages between 20 and 65 years. The chart was placed at a testing distance of 3m and a forced choice procedure was employed. Enough time was left to allow adapting by the subject. Results: The results showed that mean contrast sensitivity values were a 26 % lower for lower surround luminances. Percentages values are as follow: 78.13 % of subjects improved their contrast sensitivity result with a higher illuminated surround, 20.31 % of them did not change their contrast sensitivity and only a 1.36 % of the observers had worse contrast sensitivity with a brighter surround. Conclusion: This variation suggests that in clinical measurements this parameter should be more taken into account than actually is. The control of lighting measurement should be carefully considered when controlling the progress, treatment and rehabilitation of pathological conditions.
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