This retrospective case series compares the outcomes of patients who underwent trabeculectomy with those who received glaucoma drainage devices (GDDs) to control IOP after penetrating keratoplasty (PK).
Study design
Researchers examined records from 84 eyes that had undergone penetrating keratoplasty and subsequently had incisional glaucoma surgery at a tertiary eye-care center between 1991 and 2017. Patients underwent trabeculectomy with (n=42) or without (n=12) anti-metabolites (AMs), or had a glaucoma drainage device (GDD) implanted (n=30).
The study reports the rates of IOP success (<22 mm Hg), corneal graft survival and postoperative ocular complications.
Outcomes
Almost 70% of patients achieved IOP success at 3 years. When stratified by group, success rates were 58.3% in the trabeculectomy group, 64.3% in trabeculectomy with AM group and 86.7% in the GDD group (P=0.047) at final follow-up.
There were no statistical differences between groups for corneal graft survival or ocular complications. However, the GDD group showed a trend toward reduced graft survival.
Limitations
The cumulative probability of graft survival at 2 years was reported as 61% before glaucoma surgery and may not differ significantly from survival rates after surgery. Graft failure prior to glaucoma surgery was already present in 20% of the study eyes.
The retrospective nature and non-randomized study design could introduce potential biases. The original reason for PK was not accounted for, which may affect the overall graft survival.
Clinical significance
When compared with trabeculectomy, this study suggests that GDDs are more successful than trabeculectomy at controlling IOP after PK. However, GDDs may increase the corneal graft failure rate. Trabeculectomy without AM has limited ability to control IOP after penetrating keratoplasty, despite having a similar complication rate as other incisional glaucoma surgeries.