Frequency and Risk Factors for Neovascular Glaucoma After Vitrectomy in Eyes with Diabetic Retinopathy: An Observational Study

INTRODUCTION: Vitrectomy is one of the main treatments for proliferative diabetic retinopathy (PDR). Postoperative neovascular glaucoma, in which it is difficult to obtain satisfactory results using conventional filtering surgery, is one of the most serious complications of vitrectomy. It often requires destructive surgery, such as ciliary body photocoagulation or freezing, and the outcome with regard to visual acuity (VA) is extremely poor. The purpose of this study was to evaluate the prevalence of neovascular glaucoma (NVG) after modern vitrectomy techniques and investigate how variables assessed before and after vitrectomy are associated with patients who develop NVG after PDR surgery. METHODS: This was an observational study including the medical records of patients who underwent vitrectomy for PDR at Tianjin Eye Hospital from June 2014 to July 2016, were followed for at least 24 months postoperatively, and NVG developed within 2 years after surgery was recorded. Each patient underwent complete preoperative ophthalmic examinations in both preoperative and follow-up appointments. Factors associated with survival were determined using the Kaplan–Meier (KM) survival analysis to calculate the incidence of NVG after vitrectomy for PDR. Multivariable analysis was performed with the Cox regression proportional hazards model to verify the results of the analysis and eliminate interference factors between variables. All statistical analyses were performed using R statistical software (http://www.r-project.org) for Windows. RESULTS: In all, 238 patients (238 eyes) fulfilled the study criteria. NVG occurred in 11 of 238 eyes (4.6%). The percentages of NVG development after vitrectomy at 6, 12, and 24 months were 0.42%, 3.3%, and 4.6%, respectively. After step analysis, multivariable regression identified preoperative high intraocular pressure (IOP) combined with retinal vein occlusion (RVO), severe PDR, no postoperative intravitreal injection of ranibizumab (IVR), and higher HbA1c levels as significant predictors of NVG. CONCLUSION: Preoperative high IOP combined with RVO, severe PDR, no postoperative intravitreal injection of ranibizumab (IVR), and higher HbA1c levels are significant predictors of NVG after vitrectomy.