Graft failure after penetrating keratoplasty in eyes with Ahmed valves

Abstract

Purpose: To determine incidence and risk factors for graft failure following penetrating keratoplasty (PK) in eyes with Ahmed valves (AV).

Design: Retrospective, observational cohort study.

Methods: Patients who underwent PK after AV implantation (both performed at our institution through 2004) were studied. Intervals to graft failure (defined as either dysfunction [stromal thickening with retention of clarity] or decompensation [central microcystic edema or loss of clarity]) were analyzed using Kaplan-Meier technique. Risk factors for graft failure were analyzed using Cox proportional hazard models.

Results: Included were 77 eyes (77 patients; first procedure 1993). Following PK, 40 eyes (52%) required increased numbers of glaucoma medications; 10 eyes (13%) required additional glaucoma drainage device(s). Graft failure at 1, 2, and 3 years was 42.4% (95% confidence interval: 32.0%-54.6%), 57.1% (45.6%-69.1%), and 59.1% (47.5%-71.2%), respectively. Prior PK (HR 2.38, P = .006) and stromal vessels (HR 2.90, P = .0005) were associated with increased risk of graft failure. Use of glaucoma medications (HR 0.27, P = .009) and evidence of lower intraocular pressures (IOP) during follow-up (excluding hypotony; HR 0.92, P = .010) were associated with reduced risk of graft failure. Endothelial rejection episodes were observed in 13 eyes (17%); however, rejection was not a risk factor for graft failure (P = .98).

Conclusions: Long-term survival of corneal grafts is poor in eyes with AV. The majority of graft failures are associated with progressive loss of endothelial function, without observed immunologic rejection. Despite the presence of an AV, escalation in glaucoma therapy often follows PK; graft failure may be related to poor IOP control.