Incidence and risk factors for post-penetrating keratoplasty glaucoma: A systematic review and meta-analysis

OBJECTIVES To establish the incidence and risk factors for post penetrating keratoplasty glaucoma (PKKG). METHODS Studies published between 1947 and 2016 regarding penetrating keratoplasty (PK) were identified using an electronic search and reviewed. For search purpose, PKKG was defined as ocular hypertension (> 21mmHg) after PK. The incidence and risk factors of PKKG were extracted for all studies. Pooled incidence, odd ratios (ORs) and 95% confidence intervals (CIs) were calculated. RESULTS Thirty studies reporting on 27146 patients were included in the analysis of the incidence and risk factors for PKKG. Exact PKKG definitions used in the literature could be classified in to three subgroups: I, ocular hypertension (> 21mmHg) after PK; II, I plus > 4 weeks medical treatment required; III, II plus treatment escalation among patients with preexisting glaucoma. Overall (Definition I) pooled incidence in all studies was 21.5% (95% CI 17.8%, 25.7%). The incidence varied according to different definitions. The highest incidence value was found when only studies using Goldmann tonometer were included (22.5%), while the lowest incidence was found when a strict definition was used and steroid-induced PPKG was excluded (12.1%). The incidence was higher in patients with preexisting glaucoma, bullous keratopathy (BK), aphakia, pseudophakia, failed graft, and surgical indication of trauma. A triple procedure (combined PK with extra capsular cataract extraction and intraocular lens implantation) was not identified as being associated with the increased risk for PKKG. CONCLUSIONS The overall pooled incidence of PKKG was 21.5%, but it varied according to the criteria used to define the presence of PPKG. Strong risk factors for PKKG included preexisting glaucoma and aphakia, while modest predictors included pseudophakia, regrafting, and preoperative diagnosis like BK and trauma. There may not be sufficient evidence to identify a significant association between a triple procedure and PKKG.