Effect of phacoemulsification on intraocular pressure and bleb function in eyes with previous trabeculectomy

Abstract

AIM: To observe the intraocular pressure(IOP)control and bleb function after phacoemulsification in patients with previous history of successful/qualified success mitomycin-C augmented trabeculectomy.METHODS: This was a retrospective cohort study. Data of patients who had undergone trabeculectomy between 1st January 2013 to 31st Dec 2015 with subsequent cataract surgery were extracted from server. All patients had previous either success/qualified success trabeculectomy done. They went through uncomplicated phacoemulsification via clear corneal incision. Postoperative follow-up, review of bleb and IOP readings using Goldmann tonometer were taken. Details that were investigated include postoperative IOP control, visual improvement, number of anti-glaucoma medications, as well as the timing from trabeculectomy to phacoemulsification. Comparison with control group was made.RESULTS: Fifteen eyes from thirteen patients fulfilled the criteria for study and had undergone uncomplicated phacoemulsification on a post-trabeculectomy eye. Two of the eyes had secondary glaucoma while the other thirteen had primary glaucoma. All phacoemulsifications were done at least 6mo after trabeculectomy(mean 14.7±4.3mo). There was only 1 eye(6.7%)requiring anti-glaucoma medications before the cataract surgery. This number increased to 4(26.7%)at 1-year post-phacoemulsification. The number further increased to eight(53.3%)at 2y post-phacoemulsification. The number of anti-glaucoma drops needed after surgery at 2y ranged from 2-4. In all the 15 eyes, there was no statistically significant change in IOP control between pre-cataract surgery(mean 13.4±2.9 mmHg)compared to 1y(mean 14.1±3.2 mmHg, P=0.357)and 2y(mean 15.1±3.3 mmHg, P=0.212)post-phacoemulsification. Visual improvement after phacoemulsification however is significant, from a preoperative average visual acuity of LogMAR 1.52±1.00 to a postoperative average visual acuity of 0.53±0.54(P=0.000, paired t-test). CONCLUSION: This analysis shows significant visual improvement following cataract surgery in post-trabeculectomy patients without compromising IOP control. However, a reduced bleb function is noted following the surgery evidenced by the increase in number of anti-glaucoma drops used after surgery especially two years after the cataract surgery. Patients should be counselled regarding the possibility of restarting on anti-glaucoma medications post-phacoemulsification. The timing and sequence of cataract and glaucoma surgery should be optimized for best outcome.

Keywords

• trabeculectomy
• post-trabeculectomy phacoemulsification
• phacoemulsification
• bleb function
• intraocular pressure