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Proceedings Paper

Visual evoked potential measurement of contrast sensitivity in a case of retinal laser injury reveals visual function loss despite normal acuity
Author(s): Randolph D. Glickman; Joseph M. Harrison; Harry Zwick; Harold G. Longbotham; Charles S. Ballentine; Bennie Pierce
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Paper Abstract

Although visual function following retinal laser injuries has traditionally been assessed by measuring visual acuity, this measure only indicates the highest spatial frequency resolvable under high-contrast viewing conditions. Another visual psychophysical parameter is contrast sensitivity (CS), which measures the minimum contrast required for detection of targets over a range of spatial frequencies, and may evaluate visual mechanisms that do not directly subserve acuity. We used the visual evoked potential (VEP) to measure CS in a population of normal subjects and in patients with ophthalmic conditions affecting retinal function, including one patient with a laser injury in the macula. In this patient, the acuity had recovered from <EQ 20/100 initially after the exposure, to 20/16 at the time of this investigation (5 months post exposure). Visual stimuli consisted of counterphasing, sinusoidally-modulated luminance gratings presented at various spatial frequencies. VEPs were recorded with a gold cup electrode on the occipital scalp, and were demodulated in real time by a lock-in amplifier referenced to the stimulus counterphase frequency. As each grating was presented, its contrast was swept logarithmically from 0% to 50% over a 12-sec epoch. The CS was scored as the reciprocal of the lowest contrast within the sweep which elicited a response synchronized to the counterphase frequency. We found a CS deficit that appeared for a 3 degree(s) test field but not for larger test fields. These data indicated that contrast sensitivity measurements may reveal alterations in visual neural processing mechanisms not detected with standard clinical tests of acuity.

Paper Details

Date Published: 1 April 1996
PDF: 8 pages
Proc. SPIE 2674, Laser-Inflicted Eye Injuries: Epidemiology, Prevention, and Treatment, (1 April 1996); doi: 10.1117/12.237516
Show Author Affiliations
Randolph D. Glickman, Univ. of Texas Health Science Ctr. at San Antonio (United States)
Joseph M. Harrison, Univ. of Texas Health Science Ctr. at San Antonio (United States)
Harry Zwick, Walter Reed Army Institute of Research (United States)
Harold G. Longbotham, Conceptual MindWorks Inc. (United States)
Charles S. Ballentine, Univ. of Texas Health Science Ctr. at San Antonio (United States)
Bennie Pierce, Conceptual MindWorks Inc. (United States)


Published in SPIE Proceedings Vol. 2674:
Laser-Inflicted Eye Injuries: Epidemiology, Prevention, and Treatment
Bruce E. Stuck; Michael Belkin, Editor(s)

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