The best thickness of cornea graft from SMILE surgery as patch graft in glaucoma drainage implant surgery

OBJECTIVE: The aim of this study was to determine the best thickness of corneal slices acquired from femtosecond laser surgery—small incision lenticule extraction (SMILE surgery) as patch graft in glaucoma drainage implantation surgery. METHODS: This study is a prospective randomized study. Patients who received glaucoma drainage implantation from September 2016 to November 2018 were observed. The patients were randomly divided into 3 groups. Group A included 102 cases (104 eyes), receiving 1 layer (120–150 μm) of allogeneic lamellar corneal tissue as the graft. Group B included 117 cases (120 eyes), receiving 2 layers of lamellar corneal tissue from one donor. Group C included 109 cases (111 eyes), using 3 layers of lamellar corneal tissue from 2 donors. The intraocular pressure, corneal graft, conjunctiva stromalysis, drainage tube exposure, and drainage plate were observed. RESULTS: Patients were followed up for 6 to 33 months. The intraocular pressure was significantly reduced after surgery in all three groups. Conjunctiva stromalysis and drainage tubes were exposed in 3 eyes (3%) in group A and 1 eye (0.8%, a special case which has nystagmus and the plate was placed infratemporally) in group B, whereas no conjunctiva stromalysis or tube exposure was reported in group C. CONCLUSIONS: The corneal graft acquired from SMILE surgery can effectively prevent drainage tube exposure and give patients a better cosmetic appearance. Two layers of lamellar corneal tissue (240–300 μm) may be the best suitable thickness because it can effectively reduce tube exposure and rejection. In some special cases, 3 layers of lamellar corneal tissue are needed.