This prospective interventional study assessed the effects of repeated intraocular pressure (IOP) using Goldmann applanation tonometry and applanation resonance tonometry in six volunteers. Previous literature supports IOP reduction using repeated applanation tonometry. Repeated IOP measures were taken alternately on 12 eyes for one hour using oxybuprocaine / fluorescein in the right eye and tetracaine in the left. The left eye was photographed before and repeatedly for 20 minutes after the IOP measurements. To minimise mechanical influence, the same volunteers received the same amount of anaesthetic drops for one hour but without repeated IOP measurements. A total of 120 or 132 IOP measurements were performed per eye in one hour. Side-effects included punctate corneal erosions in four eyes with tetracaine. The results indicated a significant IOP reduction with both applanation methods greater with oxybuprocaine. The reduction was for the oxybuprocaine-treated eyes, -4.4mmHg and -3.8mmHg, respectively and in tetracaine eyes, -2.1mmHg. Additionally there was a significant drop in anterior chamber volume immediately after the IOP measurements that returned to the original level after two minutes. After one hour of receiving anaesthetic eye drops (without IOP measurements), the IOP decreased significantly in the oxybuprocaine eye for both methods, -3.1 and -1.7mmHg, respectively, but not in the tetracaine eye (P=0.72). The authors postulate that the significant reduction of IOP seen with both topical anaesthetics is possibly due to the anaesthetic effect and the movement of aqueous humor due to mechanical applanation.

Effects of topical anaesthetics and repeated tonometry on intraocular pressure.
Johannesson G, Hallberg P, Eklund A, et al.
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Nana Theodorou

BMedSCi (Hons) PhD, Sheffield Teaching Hospitals NHS Foundation Trust, Clinical Research Office, 11 Broomfield Road, Sheffield, S10 2SE, UK.

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