Persistent hypotony after trabeculectomy: incidence and associated factors in the Collaborative Bleb-Related Infection Incidence and Treatment Study.

PURPOSE: To investigate the incidence of and factors associated with persistent hypotony after trabeculectomy with mitomycin C in the Collaborative Bleb-Related Infection Incidence and Treatment Study (CBIITS), a 5-year prospective multicenter study.

METHODS

A total of 955 eyes of 955 patients who underwent trabeculectomy with mitomycin C were studied. Surgical failure was defined as insufficient intraocular pressure (IOP) reduction (IOP > 21 mmHg or <20 % IOP reduction, or further glaucoma surgeries), loss of light perception, or persistent hypotony (IOP ≤ 5 mmHg persisting for >6 months). Factors associated with persistent hypotony in eyes with sufficient IOP reduction were determined by survival analysis and logistic regression analysis.

RESULTS

The cumulative probabilities of surgical success and persistent hypotony at 5 years were 62.0 ± 1.7 % (±standard error) and 7.7 ± 0.9 %, respectively. In 685 eyes with sufficient IOP reduction, preoperative IOP (mmHg), limbus-based conjunctival flap, or choroidal detachment that occurred within 6 months of the surgery were significant risk factors for persistent hypotony [Cox proportional hazards regression model: hazard ratio, 0.95, 2.27, 3.24; 95 % confidence interval (CI), 0.91-0.98, 1.21-4.23, 1.51-6.95; P = 0.005, 0.01, 0.003, respectively]. Bleb infection and final visual acuity (logarithm of the minimal angle of resolution) were significantly associated with persistent hypotony (logistic regression: odds ratio, 8.74, 1.37; 95 % CI, 1.89-40.4, 1.03-1.82; P = 0.006, 0.029, respectively).

CONCLUSIONS

In the CBIITS, eyes with successful IOP reduction, a limbus-based conjunctival flap, lower preoperative IOP, and choroidal detachment that occurred within 6 months of the surgery were identified as risk factors for persistent hypotony.