This paper serves a twofold purpose. Some of the effects of blur of the retinal image upon perimetric thresholds are considered, and a clinical procedure is presented which utilizes these characteristics in order to provide a quantitative estimate of retinal contour. The method does not provide a measure of the true contour, but rather provides a precise reference or relative contour which may be compared with that obtained in other portions of the retina, or which may be compared with a similar set of determinations obtained at a different time. The procedure is based upon the assumption that the contrast or luminous increment threshold is lowest when the perimetric test target, imaged upon its corresponding retinal area, is focused upon the retina. The clinical method permits quantitative determination of shifts in a fore-and-aft direction of the retinal receptors in that part of the visual field usually studied with a
FANKHAUSER F, ENOCH JM. The Effects of Blur upon Perimetric Thresholds: A Method for Determining a Quantitative Estimate of Retinal Contour. Arch Ophthalmol. 1962;68(2):240–251. doi:10.1001/archopht.1962.00960030244016
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