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Investigative Ophthalmology & Visual Science, Vol 34, 1691-1701, Copyright © 1993 by Association for Research in Vision and Ophthalmology

ARTICLES AND REPORTS

Magnification perimetry

K Latham, D Whitaker, JM Wild and DB Elliott
Department of Vision Sciences, Aston University, Birmingham, United Kingdom.

PURPOSE. The authors used a method of spatial scaling to quantify the eccentricity-related decline in differential light sensitivity as a function of visual field meridian and age. METHODS. Differential light threshold at the fovea was measured in two groups of subjects of differing age (young mean age, 23.6 yr; standard deviation, 2.4 yr; elderly mean age, 69.6 yr; standard deviation, 6.2 yr) using a Goldmann size I stimulus moving across fixation at 1 degree/sec. With luminance kept constant, eccentricity thresholds for kinetic stimuli of increasing magnification were then measured. The results were analyzed in terms of the E2 value, which specifies the eccentricity at which the stimulus size must double to maintain performance equivalent to that at the fovea. RESULTS. For the young subjects, eccentricity thresholds increased linearly with an increase in stimulus diameter for most meridians. E2 varied between 5-12 degrees, depending on the meridian, and showed the same meridional trend as that of retinal ganglion cell distribution, although the magnitudes of E2 were different. For the elderly subjects, the eccentricity thresholds increased in a nonlinear manner with the stimulus diameter. CONCLUSIONS. Further factors, such as spatial summation, must also determine the eccentricity dependence of the differential light threshold because ganglion cell density decreases at a much faster rate than the differential light threshold. The most marked effects of age on differential light sensitivity occur at the fovea and beyond 20 degrees in the peripheral field, with a relative sparing in the pericentral area.


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W. H. Swanson, J. Felius, and F. Pan
Perimetric Defects and Ganglion Cell Damage: Interpreting Linear Relations Using a Two-Stage Neural Model
Invest. Ophthalmol. Vis. Sci., February 1, 2004; 45(2): 466 - 472.
[Abstract] [Full Text] [PDF]


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