Intraocular Pressure Changes in the Contralateral Eye after Glaucoma Surgery

Précis: Glaucoma surgery in 1 eye can result in significant intraocular pressure (IOP) elevation in the fellow eye in a significant percentage of subjects. This effect is more pronounced following glaucoma drainage device implantation and in subjects developing postoperative hypotony in the first eye. Purpose: The aim was to investigate the course and magnitude of IOP changes in contralateral eyes following glaucoma surgery. Patients and Methods: We studied 131 glaucoma patients undergoing surgery. IOP changes in fellow eyes and the number of glaucoma medications were recorded for 6 months. Both normal and glaucomatous fellow eyes were included. Patients on preoperative acetazolamide were analyzed separately. IOP change ≥4 mm Hg or 20% increase from baseline values was considered significant. Results: Baseline IOP in fellow eyes was 13.1±3.3 mm Hg which increased significantly at all-time points with a peak at 1 week (mean increase: 3.1±3.2 mm Hg) gradually decreasing up to 6 months (mean increase 0.9±2.1 mm Hg). The number of fellow eyes with clinically significant IOP elevation at 1 day, 1 week, and 1, 3. and 6 months was 47, 76, 47, 31, and 37 showing mean IOP rise of 4.5±2.3 (38.5%), 5.4±1.8 (48.5%), 4.8±1.6 (44.2%), 3.7±1.3 (36.5%), and 3.2±1.3 (32.6%) mm Hg, respectively. Medications were added to 18 fellow eyes (including 10 initially "normal" eyes) while 7 other fellow eyes required surgery. Significant IOP elevation in fellow eyes was associated with tube shunt surgery (P<0.008 at all-time points), a diagnosis of glaucoma following cataract surgery, IOP ≤5 mm Hg on the first postoperative day (P=0.002) and use of preoperative acetazolamide. Conclusion: Glaucoma surgery was associated with IOP elevation in fellow eyes in a significant number of subjects and suggests that IOP in the unoperated eye should also be checked at postoperative visits.