Abstract
Purpose: :
Contrast sensitivity (CS) was reported to be impaired in glaucomatous neuropathy. In this study we used a simple computerized rapid test for foveal CS to demonstrate difference between glaucomatous and non–glaucomatous patients under photopic and mesopic conditions.
Methods: :
Glaucoma patients (eyes=33) and age matched controls (eyes= 22) with visual acuity of 20/30 or better participated. Each subject underwent a comprehensive ocular examination, including perimetry. Foveal CS was measured by a computerized algorithm, using two procedures of a psychophysical testing: transient presentation of the target in a two temporal alternative forced–choice procedure; and a static method in four spatial force choice procedure. The targets were Gabor patches with spatial frequencies of 1.5 to 9 cpd. The test was carried out monocularly, first under photopic conditions, followed by dark adaptation for 1 minute, and then mesopic conditions. The mesopic testing was conducted in a completely darkened room, with the monitor covered with neutral density filter, allowing luminance of only 0.03 cd/m2.
Results: :
Significantly lower foveal CS was found in glaucomatous patients under both photopic (35–45% lower) and mesopic conditions (30–40% lower), in all spatial frequencies (p<0.05). The difference between photopic and mesopic CS values were lower in the glaucoma group than the controls, corresponding to difficulty in night vision in glaucomatous patients.
No correlation was found between contrast sensitivity and visual field (mean deviation).Both the transient and static methods yielded similar results and were significantly correlated (p<0.05); the static method was faster and more convenient for the patients.
Conclusions: :
The results indicate that disruption of central visual function may occur in glaucoma, despite good visual acuity. The similarity between the results of the two testing methods implies that the static method, which is the shorter and easier out of the two, may be used in future research. Further research is necessary in order to establish CS testing role in the screening and monitoring of glaucoma.
Keywords: contrast sensitivity • optic disc • intraocular pressure