The effects of acetazolamide on electroretinogram B-wave amplitude in albino rabbits

Acetazolamide affects performance on the Nagel II anomaloscope

BACKGROUND

Recent reports have indicated that acetazolamide alters human electroretinograms. We wished to determine the effects of administering acetazolamide on performance on the Nagel II anomaloscope.

METHODS

We tested 15 subjects matches of blue-green light to a mixture of blue and green lights (luminance match) on a Nagel type II anomaloscope 2.5 h after ingesting 500 mg of acetazolamide or a placebo.

RESULTS

The mean of the luminance settings for the subjects was 54.4 for the placebo condition and 58.5 for the acetazolamide condition. The mean difference of 4.1 was statistically significant, indicating that following ingestion of acetazolamide subjects were less sensitive to a blue-green light. In two supplementary experiments we tested (1) a second group of four normal subjects using the Nagel type II anomaloscope and (2) the previously untreated eyes of four patients with primary open-angle glaucoma before and after placing them on acetazolamide therapy. In both groups, more blue-green light was needed to make the match after ingestion of acetazolamide.

CONCLUSIONS

Acetazolamide alters the sensitivity of one or more cone populations, probably the carbonic anhydrase-containing cones. The sensitivity loss is reversible and does not appear to be clinically significant. However, the results suggest that patients administered acetazolamide should be excluded from studies which compare the color vision of glaucomatous patients to that of normals.

The effects of acetazolamide in albino rabbits, pigmented rabbits, and humans

In three separate experiments albino rabbits, pigmented rabbits, and humans were tested following administration of acetazolamide and without acetazolamide. In all three experiments, we recorded electroretinograms (ERGs) under dark adapted and light adapted conditions and measured the b-wave amplitudes. Dark adapted ERG b-wave amplitudes were increased following administration of acetazolamide as compared to control conditions, in albino rabbits, pigmented rabbits and humans. Light adapted b-wave amplitudes showed no statistically significant changes as a function of acetazolamide administration although in all three experiments there was a trend toward light adapted b-wave amplitude reduction following administration of acetazolamide. In the human experiments, ERG a-wave amplitudes were also measured. Light adapted a-wave amplitudes were reduced following administration of acetazolamide. In the human experiments, several behavioral tests were performed, including L'Anthony desaturated D-15, Farnsworth-Munsell 100 hue, Cogan-Gunkel chromatograph, Nagel anomaloscope, Goldmann-Weekers dark adaptometry. There were no consistent changes in the human dark adaptation thresholds or color discrimination, although several measures approached significance.