Does Chronic Hypotony following Trabeculectomy Represent Treatment Failure

Purpose: To measure the rate of complications from chronichypotony following trabeculectomy and clarify the definition ofpostoperative hypotony.Materials and methods: In this retrospective case-controlstudy, the rate of complications was compared between 34eyes with chronic hypotony and 34 eyes without hypotony.Chronic hypotony was defined as those eyes with an intraocularpressure (IOP) of less than 6 mm Hg on two consecutiveclinic visits at least 3 months after trabeculectomy. Cases wereidentified from a database of two glaucoma surgeons between2010 and 2013. Outcomes measured included visual acuity,presence of choroidal effusion, hypotensive maculopathy andcataract development/progression. Factors associated withthe development of hypotony were considered using analysisof variance (ANOVA) multivariate regression.Results: Maculopathy was seen in 23.5% of hypotony eyesbut not in controls (p < 0.01). No significant difference in therate of choroidal effusion or cataract was documented betweengroups. Control eyes were more likely to remain complicationfree (58.8 vs 32.4%, p < 0.03). Spontaneous recovery fromhypotony occurred in 32.4% of hypotony eyes.Conclusion: Sight threatening complications occur morefrequently in eyes with chronic hypotony following glaucomasurgery. However, not all eyes with chronic hypotony developsight threatening complications. A definition of hypotony thatcombines IOP criteria with the presence of structural and/orfunctional changes is recommended.