The Incidence of Clinically Significant Hypotony after Trabeculectomy

PRCIS: This is a retrospective observational study investigating the congruity between numerical and clinical hypotony and the risk factors for clinical manifestations of hypotony after trabeculectomy.

PURPOSE: To identify risk factors associated with clinically meaningful hypotony after trabeculectomy.

DESIGN: Retrospective cohort study.

METHODS: Patients who underwent trabeculectomy with mitomycin-C (MMC) were included. Clinical hypotony was defined as the presence (≥ 3 wk after surgery) of choroidal detachment, hypotony keratopathy, hypotony maculopathy, or shallow anterior chamber or the need for trabeculectomy revision to resolve the hypotony at any time after surgery. Numerical hypotony was defined as intraocular pressure (IOP) ≤5 mmHg in 2 or more consecutive visits, at least one of them ≥ 3 weeks after surgery. Baseline, intraoperative, and postoperative characteristics were evaluated as potential risk factors. Univariable and multivariable analyses were conducted to assess the association between each characteristic and the presence of clinical hypotony.

RESULTS: Nine hundred ninety-two eyes were included. Two hundred eighty-four eyes (28.6%) met the criteria for numerical hypotony, 222 of which (79.9%) did not show any clinical sequelae of hypotony. 99 eyes (10%) met our criteria for clinical hypotony, whereas 42 of them (42.4%) did not have numerical hypotony. The most frequent manifestation of hypotony was serous choroidal effusion (54 eyes, 5.4%) followed by shallow anterior chamber (28 eyes, 2.8%). Thirty-four eyes (3.4%) underwent trabeculectomy revision to treat the hypotony. Asian ethnicity mitigated against the development of clinical hypotony (OR: 0.29, CI: 0.10-0.72, P =0.015) and the requirement for suture lysis postoperatively was associated with a lower risk of clinical hypotony (OR: 0.49, CI: 0.29-0.81, P =0.006).

CONCLUSIONS: A minority of eyes (20.1%) with numerical hypotony showed clinical manifestations of low IOP. Asian ethnicity and eyes that required suture lysis postoperatively tended to have less incidence of clinical sequelae of hypotony after trabeculectomy.