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L. Franssen, G.C. de Wit, J.E. Coppens, T.J. van den Berg; The Relation Between Binocular and Monocular Stray Light Measurements . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4075.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Retinal stray light, which is the cause of disability glare, can reliably be measured using the direct compensation method. The stray light parameter is a physically well-defined quantity, which can be used to describe light scattering in the eye, but it is also generally accepted as a measure for glare sensitivity. However, stray light is measured monocularly, whereas in real-life glare situations visual tasks are performed binocularly. In this study we investigated the usefulness of binocular stray light measurements, based on the direct compensation method, as a measure for binocular glare sensitivity. Methods: Monocular and binocular stray light values were measured for four subjects, by means of the direct compensation method, following a Four Alternative Forced Choice procedure. To simulate different stages of a unilateral cataract, subjects were provided with lenses with various light scattering properties in front of one of their eyes. Measurement results were compared to the relation between binocular and monocular contrast sensitivity, known from literature. Results: When the monocular stray light values of the two eyes of a subject are similar, the binocular stray light value is about the same. With a simulated unilateral cataract, measured binocular stray light values are always in between the monocular ‘normal' and ‘cataract' values. With increasing unilateral ‘cataract', the binocular stray light value first follows more or less the monocular ‘cataract' eye value, and then slightly declines to approach the monocular ‘normal' eye value, although it never reaches this value, at least for realistic cataract values. Conclusions: Binocular stray light, measured using the direct compensation method, has a value in between the two monocular stray light values. The weighting function shows a maximum for intermediate values of asymmetry between the two eyes. This is comparable to the behavior of binocular contrast sensitivity, although the precise functions are different.
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