title: Impact of a Glaucoma Severity Index on Results of Trabectome Surgery: Larger Pressure Reduction in More Severe Glaucoma.
abstract: OBJECTIVE
  To stratify outcomes of trabectome-mediated ab interno trabeculectomy (AIT) by glaucoma severity using a simple and clinically useful glaucoma index. Based on prior data of trabectome after failed trabeculectomy, we hypothesized that more severe glaucoma might have a relatively more reduced facility compared to mild glaucoma and respond with a larger IOP reduction to trabecular meshwork ablation.
  
  
  METHODS
  Patients with primary open angle glaucoma who had undergone AIT without any other same session surgery and without any second eye surgery during the following 12 months were analyzed. Eyes of patients that had less than 12 months follow up or were diagnosed with neovascular glaucoma were excluded. A glaucoma index (GI) was created to capture glaucoma severity based on visual field, number of preoperative medications, and preoperative IOP. Visual field (VF) was separated into 3 categories: mild, moderate, and advanced (assigned 1, 2, and 3 points, respectively). Preoperative number of medications (meds) was divided into 4 categories: ≤1, 2, 3 or ≥4, and assigned with a value of 1 to 4. Baseline IOP (IOP) was divided into 3 categories: <20 mmHg, 20-29 mmHg, and greater than 30 mmHg and assigned with 1 to 3 points. GI was defined as IOP × meds × VF and separated into 4 groups: <6 (Group 1), 6-12 (Group 2), >12-18 (Group 3) and >18 (Group 4). Linear regression was used to determine if there was an association between GI group and IOP reduction after one year or age, gender, race, diagnosis, cup to disc (C/D) ratio, and Shaffer grade.
  
  
  RESULTS
  Out of 1340 patients, 843 were included in the analysis. The GI group distribution was GI1 = 164, GI2 = 202, GI3 = 260, and GI4 = 216. Mean IOP reduction after one year was 4.0±5.4, 6.4±5.8, 9.0±7.6, 12.0±8.0 mmHg for GI groups 1 to 4, respectively. Linear regression showed that IOP reduction was associated with GI group after adjusting for age, gender, race, diagnosis, cup to disc ratio, and Shaffer grade. Each GI group increase of 1 was associated with incremental IOP reductions of 2.95±0.29 mmHg. Success rate at 12 months was 90%, 77%, 77%, and 71% for GI groups 1 to 4. The log-rank test suggested significant differences between GI groups.
  
  
  CONCLUSIONS
  A simple glaucoma index, GI, was created to capture glaucoma severity and a relative resistance to treatment. A higher GI was associated with a larger IOP reduction in trabectome surgery. This indicates that there is a role for AIT beyond mild glaucoma and ocular hypertension.
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Ralitsa T
authors.initials: RT
authors.lastname: Loewen
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Pritha
authors.initials: P
authors.lastname: Roy
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Hardik A
authors.initials: HA
authors.lastname: Parikh
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Yalong
authors.initials: Y
authors.lastname: Dang
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Joel S
authors.initials: JS
authors.lastname: Schuman
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Nils A
authors.initials: NA
authors.lastname: Loewen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005901:Glaucoma / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D014130:Trabeculectomy; D014794:Visual Fields