After obtaining institutional ethical committee approval (No: 2022 – 136), data of patients who underwent GATT surgery in our clinic were collected. The study followed the principles laid out in the Decleration of Helsinki. Written informed consent was taken from each patient before study. Routine preoperative gonioscopic examination was performed in all patients to ensure the presence of an open angle with identifiable angle landmarks in all four quadrants (nasal, temporal, superior and inferior).
Patients
The ophtahlmological findings of patients (⩾18 years old) who had diagnoses of either primary OAG (POAG) or secondary OAG (SOAG) and underwent GATT procedure were examined. During preoperative evaluation, patients underwent detailed ophthalmological examinations, including best corrected visual acuity (BCVA) assessment with a standard Snellen chart, slit-lamp biomicroscopic examination, gonioscopy with a Goldmann three mirror lens, IOP measurement with applanation tonometry, and dilated fundoscopic evaluation. Central 24-2 threshold visual field test with SITA-Fast strategy using Humphrey Field Analyzer (HFA-750 i, Carl Zeiss Meditec Inc., USA) and retinal nerve fiber analysis using spectral domain optical coherence tomography (Optovue OCT V 5.1, RTVue 100-2; Optovue, Fremont, CA, USA) were also performed. Snellen visual acuities were then converted to the logarithm of the Minimum Angle of Resolution (logMAR) for statistical analysis.
Inclusion criteria in the present study were, patients to be operated with GATT surgery because of the uncontrolled IOP despite maximum medical therapy, and/or intolerance to glaucoma medications (nonadherence to treatment or ocular allergy), and/ or glaucoma progression as tested by visul field examination. The patients were also asked to follow the criteria regularly for at least 6 months. Exclusion criteria in the study were, age of lower than 18, history of previous ocular surgery (except for trabeculectomy surgery) and/or trauma, any medical condition other than OAG (such as uveitis, cataract, ectopia lentis, aniridia, albinism, high axial myopi, romatologic disorders, diabetes), presence of PAS in the preoperative gonioscopic evaluation, and irregular follow-up shorter than 6 months.
Surgical procedure
All surgeries were performed under general anaesthesia by the same experienced surgeon (MG). Details of the GATT procedure were reported in the literature previously [5]. Briefly, after providing standard surgical aseptic condition, eye was draped and lid speculum was placed. The surgeon performed surgeries by sitting on the temporal site. Two side ports were placed either in the supero-nasal or infero-nasal quadrant with a 20-G microvitreoretinal blade. A temporal corneal incision was made with a 2.8 mm angled slit knife. Ophthalmic viscoelastic device (OVD) was injected into the anterior chamber. The tip of the 5-0 prolene suture was blunted with light cautery and inserted into the anterior chamber. The patient’s head was tilted away from the surgeon while the microscope was oriented towards the surgeon to get proper visualization of the nasal angle with a Swan- Jacob goniolens. A 2-mm nasal goniotomy was created using a 23-G microvitreoretinal blade and posterior wall of Schlemm’s canal was exposed. Microsurgical forceps was then used to grasp and introduce the blunted tip of the prolene suture into Schlemm’s canal. The suture was advanced through Schlemm’s canal 360° and distal tip of the suture was retrieved and externalized to create a 360° trabeculotomy. If suture advancement could not be made 360° where suture stopped at 180° within the canal, external part of the suture was pulled and externalized to complete a 180° trabeculotomy. The blood in the anterior chamber and OVD was then removed from the anterior chamber using bimanual irrigation aspiration. All incisions were hydrated. In cases where combined GATT and cataract surgery was needed, GATT was performed first followed by clear corneal phacoemulsification with IOL implantation surgery.
Postoperatively, patients were ordered with topical moxifloxacin and dexamethasone 8 times a day and topical nepafenac 6 times a day during first week. Moxifloxacin was tapered to 4 times a day after one week and stopped at two weeks. Dexamethasone was tapered gradually after first week and stopped at 3 weeks. Nepafenac was tapered to 4 times a day over two weeks and stopped at 1 month. Patients were examined on the first day, first week, first month, third month and six months postoperatively. At each visit, visual acuity, IOP, complications and the number of antiglaucoma medications used were recorded.
Complete success was defined as IOP of 21 mm Hg or lower without use of topical antiglaucoma medication and a decrease in IOP of 20% or more from the baseline IOP. Qualified success was defined as an IOP of 21mmHg or lower with use of topical antiglaucoma medication.
Assessment of postoperative PAS formation
Peripheral anterior synechia formation after surgery was evaluated at months 1, 3 and 6. Following routine ophthalmological examination, presence of PAS was assessed with a Goldmann three mirror lens in each patient under dim room light conditions. After application of topical anesthetic eye drop (0.5% proparacaine HCl) on ocular surface, concave surface of the lens was filled with a carbomer gel (Viscotears jell, Novartis, Turkey). Lens was then carefully inserted onto the patient’s cornea while the patient was looking upwards. Lens was rotated with the eye in primary position to examine the total circumference of the angle. If present, presence of PAS was noted in a quadrant base manner (nasal, temporal, superior and inferior). The extent of PAS was expressed by dividing each quadrant into three clock hours. Figure 1 shows a representative image demonstrating PAS evaluation in the study.
Statistical analysis
All data obtained from the participants were evaluated in the computer package program SPSS 13.0.1 (SPSS, Chicago, IL; license number: 9069728, KTU Trabzon). Nominal data were presented as percentages, and metric data were presented as mean ± standard deviation. The suitability of numerical data to normal distribution was evaluated with the one-sample Kolmogorov-Smirnov test. Repeated-measures analysis of variance was used to compare repeated measurements. The statistical significance level was accepted as p <0.05.