Hypotony-Associated Complications after Deep Sclerectomy: Incidence, Risk Factors, and Long-Term Outcomes

Precis: Chronic hypotony is not uncommon following deep sclerectomy (DS), but only a minor proportion of patients develop hypotony-Associated complications. Numerical hypotony does not affect the visual outcomes. This study identifies factors associated with hypotony. Purpose: To investigate the incidence and risk factors of hypotony and hypotony-Associated complications after DS. Methods: Retrospective cohort study of 1765 eyes (1385 patients) undergoing DS with or without cataract extraction between 2001 and 2020 in 2 UK centers. Chronic hypotony was defined as intraocular pressure (IOP) ≤5 mm Hg in ≥2 consecutive visits lasting >90 days or as any IOP ≤5 mm Hg associated with hypotony-related complications or requiring surgical intervention. Clinical hypotony was defined as the presence of: serous or hemorrhagic choroidal detachment, hypotony maculopathy, flat anterior chamber requiring reformation, decompression retinopathy. The incidence of hypotony was calculated with Kaplan-Meier statistics, and Cox regression was used to identify risk factors. Results: The median (interquartile range) age and follow-up were 76 (67 to 82) years and 45.4 (20.9 to 79.8) months, respectively. The incidence (95% confidence interval) of chronic and clinical hypotony at 5 years was 13.4% (11.5%-15.3%) and 5.6% (4.3%-6.9%), respectively. Sixteen eyes (15.7%) with hypotony-Associated complications had IOP >5 mm Hg. Male sex (hazard ratio [HR]: 1.89, P=0.018), non-Caucasian ethnicity (HR: 2.49, P=0.046), intraoperative bevacizumab (HR: 3.96, P=0.01), pigmentary glaucoma (HR: 3.59, P=0.048), previous vitreoretinal surgery (HR: 5.70, P=0.009), intraoperative microperforation (HR: 4.17, P<0.001) and macroperforation (HR: 20.76, P<0.001), and avascular bleb (HR: 1.80, P=0.036) were associated with clinical hypotony. Discussion: Chronic hypotony is not uncommon following DS, but clinical hypotony is infrequent. Hypotony associated-complications can occur in eyes without statistical hypotony.