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  • By Michael Vaphiades, DO

    The authors tested the hypothesis that treatment with carbonic anhydrase inhibitor brinzolamide (Azopt) eye drops has a beneficial effect on nystagmus. They administered the drops to a 68-year-old man with infantile nystagmus who had shown improvement with systemic acetazolamide and found that the drops resulted in improved foveation over a broad range of gaze angles, with therapeutic effects equivalent to oral carbonic anhydrase inhibitors. The authors conclude that brinzolamide eye drops could become the preferred treatment for infantile nystagmus since the therapy has no systemic side effects and is faster acting than its oral counterpart.

    The subject was given one drop of topical brinzolamide (Azopt) three times daily in each eye for three days. His eye movements were recorded using a high-speed digital video recording system twice on day one (one hour and five hours after the first administration of brinzolamide) and once on days two through five and on day 12. Nystagmus waveforms were analyzed by applying the eXpanded Nystagmus Acuity Function (NAFX) at different gaze angles and determining the longest foveation domain (LFD), and compared to previously published data from the same subject after the use of systemic acetazolamide, contact lenses and convergence and to other subjects before and after eye muscle surgery for infantile nystagmus syndrome (INS).

    The authors found that topical brinzolamide improved foveation by both a 51.9 percent increase in the peak value of NAFX function (from 0.395 to 0.600) and a 50 percent broadening of the NAFX vs. Gaze Angle curve (the longest foveation domain increased from 20° to 30°). The improvements in NAFX after topical brinzolamide were equivalent to the effects of systemic acetazolamide or eye muscle surgery and were intermediate between those of soft contact lenses or convergence. Topical brinzolamide and contact lenses had equivalent LFD improvements and were less effective than convergence.

    The authors conclude that although a prospective clinical trial is needed to prove efficacy or effectiveness in other subjects, an eyedrop-based therapy for INS may emerge as a viable addition to optical, surgical, behavioral and systemic drug therapies.