Intraocular pressure changes in the contralateral eye after topical treatment: Does an 'ophthalmotonic consensual reaction' exist?

Background: The existence of "ophthalmotonic consensual reaction," a contralateral change in intraocular pressure in the fellow eye induced by treatment of the first eye only, was suggested in 1924. Since then, the validity of this mechanism has been controversial. Objectives: To assess intraocular pressure changes in the contralateral fellow eyes of patients treated with IOP-lowering medication in one eye, and investigate the existence of an ophthalmotonic consensual reaction. methods: The study population included 38 patients with newly diagnosed bilateral ocular hypertension or early open angle glaucoma. One eye of each patient was randomly treated with one of five compounds: prostaglandin analogues, beta-blockers, alpha-2 agonists, carbonic anhidrase inhibitors and a combination therapy: dorzolamide hydrochloridetimolol maleate (Cosopt®, Merck Sharpe & Dohme). The eye with the higher baseline IOP was selected to be the treated eye. After 3 weeks a masked examiner measured the IOP in both the treated and untreated eye. results: Mean IOP of the treated eyes at baseline was 26.1 ± 4.2 mmHg and at follow-up 20.2 ±2.9 mmHg, a reduction of IOP from baseline of -6 ± 3.8 mmHg, a mean percent reduction of -22 ± 10.1%. In the contralateral eyes, the mean IOP at baseline was 24.2 ± 3 mmHg and 23.1 ± 3.1 mmHg at follow-up; IOP reduction from baseline was -1.2 ± 1.8 mmHg, or mean percent reduction -4.7 ± 7.1%. A major contralateral IOP decrease was seen only in the beta-blockers and the combination (Cosopt®) treatment groups (-6.1 ± 8.3% and -12.3 ± 8.3% mean percent reduction, respectively, P < 0.05). The contralateral eyes in the prostaglandin analogues, CAI or α2-agonist groups showed only a small change in IOP (-2.6 ± 4.6%, -3.2 ± 2.6%, +0.7 ± 3.3%, mean percent reduction, respectively, P < 0.05). conclusions: The existence of an ophthalmotonic consensual reaction was not supported.