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Editors Selection IGR 24-3
Medical Therapy: Is IOP after topical treatment centrally regulated?
Comment by Tony Realini on:
27585 Intraocular pressure changes in the contralateral eye after topical treatment: Does an 'ophthalmotonic consensual reaction' exist?, Newman H; Kurtz S; David R, Israeli Medical Association Journal, 2010; 12: 568-571
Newman et al. (2058) have conducted a small but well-designed study to explore the possibility of central regulation of intraocular pressure (IOP). They asked whether topical IOP-lowering therapy in one eye produced IOP reductions in the untreated fellow eye. Thirty-eight treatment-naïve subjects with newlydiagnosed ocular hypertension or open-angle glaucoma IOP > 22 were treated for six weeks with a variety of IOP-lowering drug classes for three weeks in the eye with the higher IOP. IOP was measured in both eyes in masked fashion both before and after therapy at approximately the same time of day on each visit. IOP in the treated eye dropped by 6 mmHg after three weeks, while IOP in the untreated eye dropped only 1.2 mmHg over the same time interval. Despite small numbers in drug class subgroups, a careful examination of subgroup responses is revealing. Nine subjects received prostaglandin analogues; in this group, the treated eye dropped 7.3 mmHg while the untreated eye dropped only 0.7 mmHg. In contrast, eleven subjects received beta-blockers; in this group, the treated eye dropped 4.9 mmHg while the untreated eye dropped 1.5 mmHg. Six more subjects received the timolol/dorzolamide fixed combination; in this group, the treated eye dropped 10.3 mmHg while the untreated eye dropped 3.2 mmHg. The investigators correctly concluded that the responses in subjects receiving a beta-blocker (alone or in fixed combination) drove the overall finding. Beta-blockers are known to have a contralateral crossover effect probably mediated by systemic absorption. Their study provides no evidence for a centrally mediated ophthalmotonic consensual reaction, as was first proposed by Belgian ophthalmologist Liege Weekers in 1922.
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