This study was a retrospective case series of consecutive patients undergoing intravitreous injection of ranibizumab with a diagnosis of PDR who were planned to take vitrectomy after IV. Records of 126 patients were retrospectively reviewed in the study from January 2015 to January 2017 in the Beijing Tongren Eye center. This study was approved by the Ethics Committee of Beijing Tongren Hospital and adhered to the tenets of the Declaration of Helsinki.
Inclusion criteria: 1) Patients diagnosed with PDR, 2) patients took an intravitreous injection of ranibizumab before vitrectomy, 3)Records with intraocular pressure (IOP) values measured before and after intravitreous injection of ranibizumab (IVR). Exclusion criteria: 1) patients failed to finish at least 1-month follow-up after vitrectomy; 2) patients with history of preexisted open-angle glaucoma, 3) patients with preexisted narrow/closed angle, 4) patients received an intravitreous or subtenon injection of corticosteroids or steroid eye drops within the latest six months, 5) uncontrolled neovascular glaucoma by at least 3 kinds of antiglaucoma medicines.
All patients underwent comprehensive ophthalmological examinations, including best-corrected visual acuity (BCVA) testing using a decimal VA chart, slit-lamp biomicroscopy, IOP measurement, dilated fundus examination with indirect ophthalmoscopy, color fundus photograph, optical biometry, optic coherent tomography (OCT)，B scan. Gonioscopy was considered when iris neovascularization was found. BCVA, the axial length, the presence of posterior vitreous detachment ( PVD, was defined as the presence of a Weiss ring and visible posterior vitreous cortex under the slit-lamp biocular biomicroscopy examination by the same surgical doctoror by B scan, PVD was confirmed by findings in triamcinolone acetonide-assisted vitrectomy ), history of diabetes mellitus, history of visual acuity decrease, use of insulin, history of retinal photocoagulation for diabetic retinopathy, sex, age, refraction, presence of iris neovascularization, intraocular lens (IOL), dense vitreous hemorrhage that obscured the view of optic disc and details of fundus, tractional retinal detachment that threatened the central vision or caused repeated vitreous hemorrhage, fibrovascular membrane involving the disk, presence of macular edema were recorded as the baseline data.
An intravitreous injection of ranibizumab 0.5 mg was performed 1-10 days before vitrectomy. All injections were performed by one surgeon. All patients underwent a 3-port pars plana 23-gauge vitrectomy under general anesthesia. Phacoemulsification surgery was performed before vitrectomy in case of necessary determined by the surgeon. The presence of PVD, a tractional retinal detachment that threatened central vision, fibrovascular membrane involving the disk were confirmed in the vitrectomy after removal of dense vitreous hemorrhage and recorded. The silicon oil tamponade and laser points during vitrectomy were recorded.
All patients underwent a complete series of IOP measurements with an air tonometer (Nidek, Tonoref 3). IOP was measured before IVR, 30min, 2h, 1d, 2d, 3d after intravitreous injection. If elevated IOP occurred, IOP was measured twice a day until the IOP was controlled. The ghost cell glaucoma was defined as the presence of both high IOP and ghost cells in the anterior chamber. Follow-up visits were scheduled at 1,2,7,14 and 30 days after the initial surgery. The examination included BCVA, IOP, slitlamp，dilated fundus examination.
Statistical analysis was performed using R version 3.20 (http://www. R-project.org). Patient characteristics were retrieved from their medical charts and recorded in Epidata EntryClientversion188.8.131.52 (http://epidata.dk). BCVA results were converted to a logMAR value for statistical analysis. Mean and standard deviation (SD) were calculated for continuous variables with a normal distribution. Median with quartiles was calculated for continuous variables with a non-normal distribution. The t-test or Mann-Whitney U test was carried out for continuous variables. The Chi-square test or Fisher’s exact test was carried out for discrete data. To explore the potential factors that might influence the occurrence of ghost cell glaucoma, we divided the patients into two groups, patients with ghost cell glaucoma and patients without ghost cell glaucoma after IVR. Several factors including duration of diabetes mellitus, onset of decrease vision, use of insulin, pre-existence of pan-retinal photocoagulation (PRP) for DR, refraction error, axial length, sex, age, presence of PVD, presence of iris neovascularization (NVI), tractional retinal detachment that threatened the central vision or caused repeated vitreous hemorrhage, IOL, fibrovascular membrane involving the disk, presence of clinical significant macular edema were compared between two groups (Table1). Variables (p <=0.4) were further enrolled in a binary backward stepwise logistic regression model. One variable was included or excluded from the model each time by comparing the Akaike information criterion (AIC) value, and the model that had the lowest AIC was chosen. The model was accessed by the receiver operating characteristic curve (ROC curve).