November 1992
Volume 33, Issue 12
Free
Articles  |   November 1992
Grating, vernier, and letter acuity in retinitis pigmentosa.
Author Affiliations
  • K R Alexander
    Department of Ophthalmology and Visual Sciences, University of Illinois, Chicago College of Medicine 60612.
  • D J Derlacki
    Department of Ophthalmology and Visual Sciences, University of Illinois, Chicago College of Medicine 60612.
  • G A Fishman
    Department of Ophthalmology and Visual Sciences, University of Illinois, Chicago College of Medicine 60612.
  • J P Szlyk
    Department of Ophthalmology and Visual Sciences, University of Illinois, Chicago College of Medicine 60612.
Investigative Ophthalmology & Visual Science November 1992, Vol.33, 3400-3406. doi:
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      K R Alexander, D J Derlacki, G A Fishman, J P Szlyk; Grating, vernier, and letter acuity in retinitis pigmentosa.. Invest. Ophthalmol. Vis. Sci. 1992;33(12):3400-3406.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Grating, vernier, and letter acuities were compared in 25 patients with retinitis pigmentosa (RP), whose Snellen visual acuities were better than 20/40, to address the mechanism of visual acuity loss. For these patients with RP, all three types of visual acuity were reduced to an equivalent degree from those of a control group of 10 age-similar, visually normal subjects. The findings indicate that the visual acuity losses of these subjects with RP did not result from cone spatial undersampling (due, for example, to a random loss of foveal cones), from cone sampling irregularities (due to random alterations in foveal cone position), or from a selective loss of sensitivity to high spatial frequencies (as might result from changes in media transmission characteristics or a gain reduction in high spatial frequency mechanisms). In addition, previous studies have indicated that acuity losses in such patients with RP do not result from reductions in the quantum-catching ability of foveal cones. The most likely explanation for the equivalent losses in all three acuity types in these patients with RP appears to be an alteration in foveal spatial scale, consistent with a generalized increase in foveal intercone spacing.

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