Intereye Difference Research Articles

Delayed visual evoked potentials in chronic alcoholism.

Pattern reversal visual evoked potentials (VEPs) were studied in 80 chronic alcoholics and in 43 normal subjects. In the patient group, P2 latencies and inter-eye differences were found above the 98% confidence limit in 30%, and above the 99.9% confidence limit in 10%. An abnormal waveform was observed in 12.5% and 7.5% of the patients. VEP abnormalities showed some statistical correlation with the gamma-type of alcoholism of Jellinek, but almost no correlation was observed with a variety of clinical and laboratory data. This suggest that VEP abnormalities are unrelated to other toxic effects of alcohol on the peripheral and central nervous systems or on metabolism.

The endothelial cell damage in acute glaucoma. On the corneal thickness response to intraocular pressure.

In order to assess a possible damage to the corneal endothelium during pressure induced abnormal hydration of the cornea, 23 patients with a previous attack of unilateral acute glaucoma were photographed with a specular microscope. As compared to the healthy side, the endothelium of the affected side showed a mean decrease in cell density of 23.1%, range --4.8 to 68% (P less than 0.001). In retrospect this cell loss was found to correlate significantly to the increase in corneal thickness measured during the acute attack on first day of admission. At present examination mean central corneal thickness was identical in the affected and unaffected eye. A large variation was, however, found in the intraocular pressure of the previously attacked eye. If the subject inter-eye difference in intraocular pressure was related to the inter-eye difference in corneal thickness is significant negative correlation appeared. It is concluded that the intraocular pressure has a dual effect on the corneal hydration: if the endothelium is intact, the intraocular pressure decreases corneal thickness, whereas an increase is seen only if the endothelium is acutely damaged.

Pattern shift visual evoked responses. Two hundred patients with optic neuritis and/or multiple sclerosis.

Fifty-one patients with clinically pure optic neuritis (ON) and 149 with possible, probable, or definite multiple sclerosis (MS) were tested with pattern shift visual evoked responses (PSVER) and compared with a group of 43 normal subjects. Attention was paid to response latency, intereye latency difference, as well as differences in amplitude or duration of the major positive peak (P100). Abnormal PSVER cannot be recorded from everyone with confirmed ON. Abnormal responses were recorded from 91% of all patients (including those with MS) who had a history of ON, 57% of all MS patients, and 36% of patients without a history of ON or an abnormal eye examination. Measurements of amplitude and duration proved to be of little value in this setting. Though abnormalities of PSVER are not "specific" for ON or MS, because they also result from other disease processes, they afford more reliable, quantitative documentation of abnormal conduction in visual pathways than any other clinical test.

Cortical and subcortical mechanisms in the conditioned avoidance response to light in the albino rat

Rats have been trained on a simple conditioned avoidance response to light after undergoing unilateral ablation of the striate cortex. On completion of training, the ability of each eye alone to mediate the response has been tested. The eye ipsilateral to the cortical ablation maintains performance well, but with the contralateral eye performance is significantly impaired. With repeated testing of each eye separately, the performance with the contralateral eye shows gradual improvement so that the inter-eye difference ultimately becomes insignificant. Performance with the contralateral eye is better preserved, to a significant extent, if it is tested immediately after the ipsilateral eye than when this order is reversed. The results have been discussed in terms of the differences in central representation of the conditioned avoidance response to light at cortical and subcortical levels.

Inter-Eye Differences in Color-Perception

This report concerns a method for determining the difference in colorsensitivity of the two eyes of an observer (0), and equations are presented to show how color-appearances to one eye may be predicted from a knowledge of what the other eye sees. The basic method dates back at least to Hering, but interest has usually centered on differences in sensitivity induced by grossly different conditions of adaptation of the two eyes.' An attempt will be made here to deal specifically with intrinsic differences in color-sensitivity when both eyes are adapted to the same illumination. The data were incidental to the results of two studies previously reported from this laboratory that concerned the effects of chromatic adaptation on colorappearance.2 A binocular septum-technique was so used in those studies that a test-color could be presented to one eye adapted to a standard illuminant while a variable matching-color could be presented to the other eye adapted to the same or a different illuminant. Intrinsic inter-eye differences were completely eliminated in those studies, as in a prior study by Hunt,3 by permitting the matches made under the standard illuminant to serve as the reference-colors against which matches made with the same eye adapted to the other illuminants were compared. The difference in color-specification between the test-color presented to one eye and the matching-color seen by the other, with both eyes adapted to the same illuminant, serves as a direct measure of the difference in color-sensitivity of the two eyes and as a basis for predicting inter-eye differences in the appearance of other colors. The usable data from the first study consisted of the results for 6 Os who matched 22 test-colors with adaptation to CIE Illuminant C but with extensive opportunity for local adaptation to the testand matching-colors during the matchingprocess. The usable data from the second study comprised the results for 4 Os who matched 12 test-colors with adaptation to the same illuminant, with controlled and very limited opportunity for local adaptation while matching. Three Os were com-