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R.S. Harwerth, G. Barnes, W.F. Holt, E.L. Smith; Spatial Frequency Response Properties of Visual Field Defects From Glaucoma . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4667.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: A relative loss of spatial contrast sensitivity has been suggested as an early sign of optic neuropathy from glaucoma, but the effects of spatial frequency have not been studied systematically. The purpose of the present study was to investigate the alterations of spatial contrast sensitivity functions in areas with depressed visual sensitivity from glaucoma. Methods: By behavioral testing, perimetry by standard clinical procedures and by contrast sensitivity measurements were assessed over the time course of the development of visual field defects from experimental glaucoma in six rhesus monkeys. The contrast sensitivity stimuli were horizontally orientated Gabor patches (0.5 octave bandpass) with carrier frequencies of 0.25 – 2.8 c/deg, which were presented for 140 msec duration. Spatial contrast sensitivities were determined for locations at 3x3 deg, 9x9 deg and 15x15 deg in each visual field quadrant. The spatial frequency effects were evaluated via a fitted low–pass model for spatial contrast sensitivity functions. Results: The overall losses of contrast sensitivity were ordinally related to the depth of visual field defects with standard perimetry, but the losses in contrast sensitivity increased as a function of spatial frequency. With stimuli of 1 or 2 c/deg, the losses in contrast sensitivity usually preceded losses by standard perimetry and the depth of high frequency defects became unmmeasurable if the standard perimetry defect exceeded about 12 dB. Conclusions: Early visual field defects from glaucoma represent selective spatial frequency effects where the losses of contrast sensitivity at high spatial frequencies precede losses at lower spatial frequencies. Thus, in general the visual defects from glaucoma represent progressive spatial filtering, or blurring, with the magnitude of blur proportional to the depth of visual field defect.
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