Scleral Patch Graft Melt After Tube Shunt Surgery: Grading and Identification of Risk Factors

Purpose: To identify scleral patch graft (SG) melting trends in patients after tube shunt surgery and validate a grading scale for SG health. Methods: Patients with glaucoma who underwent tube shunt surgery with a SG were enrolled consecutively at Rutgers New Jersey Medical School from September, 2016 to June, 2017. SG images that were acquired through slit-lamp photography were graded independently by 3 researchers for surface area remaining, thickness and vascularity of the conjunctiva. Interobserver correlation coefficient (kappa) was performed for these scores using our grading system. A chart review of patient records was conducted to investigate comorbid conditions and the student t test was performed with significance P<0.05 to identify associations with SG melt. Results: In total, 67 eyes (mean age 60 +/- 20 y, 65% female, 35% male) were enrolled. In total, 124 SG images were acquired, but the 67 best captured images were evaluated by 3 graders. Mean percentage of surface area remaining area were 46.2 +/- 44.1 (kappa=0.82). The average measured surface area remaining was 6.8 mm(2) from reference of 16 mm(2). For the 3 graders, mean thickness scores were 1.0 +/- 0.9 (kappa=0.79), and mean vascularity scores were 1.1 +/- 0.6 (kappa=0.83). Time from surgery at which SG were evaluated was: 17 eyes (25%) <3 months, 11 (16%) 3 to 12 months, 8 (12%) 12 to 24 months, 16 (24%) 2 to 5 years, and 15 (23%) > 5 years. At those time point: average percentage SG remaining were 72.9, 60, 31.3, 30.7, and 33.3%, respectively (P<0.05 comparing < 1 to > 1 y) and SG thickness score 1.6, 1.2, 0.6, 0.6, and 0.7, respectively (P<0.05 comparing < 3 mo to 12 to 24 mo). The rate of SG melt (measured by surface area remaining) over time was higher in patients with ocular surface disease (P<0.01). Conclusions: SG melts gradually after tube shunt surgery with the most dramatic melt occurring after 12 months postoperatively. This simple and consistent SG grading scale has high interrater agreement and can be may be used to assess and follow graft health over time.