The Incidence of Clinically Significant Hypotony after Trabeculectomy.

PRECIS

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 (≥ three weeks 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 two or more consecutive visits, at least one of them ≥ three 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 and ninety-two eyes were included. Two hundred and 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, while 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%). 34 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).

CONCLUSION

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.