Comparison of long-term outcomes of trabeculectomy and risk factors for failure in eyes post penetrating keratoplasty or Descemet's stripping endothelial keratoplasty

Purpose: To evaluate the outcomes of trabeculectomy, graft survival, and risk factors for failure in post penetrating keratoplasty (PK) and Descemet's stripping endothelial keratoplasty (DSEK) eyes. Methods: We reviewed charts of eyes that underwent trabeculectomy for post keratoplasty glaucoma PK [25 eyes] and DSEK [14 eyes] between 1993 and 2019. The demographics, clinical features, and surgical outcomes were evaluated. Success of trabeculectomy was defined as complete when the intraocular pressure (IOP) was >5 and <= 21 mmHg without antiglaucoma medications (AGM) and qualified with AGM. Clear and compact graft was considered for graft success. Results: Median (interquartile range [IQR] preoperative IOP in post-PK eyes and post-DSEK eyes was comparable, 32 (28-38) vs. 31.5 (25-36) mmHg, P = 0.38). Median number of preoperative AGMs was comparable (P = 0.78). Median postoperative follow-up was longer in post-PK, compared with post-DSEK, 2.5 (1.3-3.3) vs. 1 (0.3-2.9) years (P = 0.05). Kaplan-Meier survival estimates for complete and qualified success of trabeculectomy at 3 years were 23.7% and 73.3%, respectively, for PK and 45.8% and 71.6%, respectively, for DSEK. Kaplan-Meier survival estimates for graft survival were 91.8% up to 3 years for PK and 100% until 2 years and 77.8% at 3 years for DSEK. Higher IOP prior to trabeculectomy was a risk factor for failure of trabeculectomy (P = 0.03) and older age was a risk factor for graft failure (P = 0.05) in PK eyes. Number of prior corneal surgeries (P = 0.05) was associated with failure of trabeculectomy and graft failure in post-DSEK eyes. Conclusion: Trabeculectomy had moderate qualified success in post-PK and DSEK eyes at 3 years. Higher pretrabeculectomy IOP and higher number of prior corneal surgeries were significantly associated with failure of trabeculectomy in PK and DSEK eyes, respectively.