Rates and Patterns of Diagnostic Conversion from Anatomical Narrow Angle to Primary Angle-Closure Glaucoma in the United States

To assess rates of diagnostic conversion from anatomical narrow angle (ANA) to primary angle-closure glaucoma (PACG) in the United States and identify factors associated with diagnostic conversion.Retrospective case-control study.Patients diagnosed with ANA between the years 2007 and 2019 were identified based on International Classification of Diseases (ICD) codes in the Optum Clinformatics Data Mart Database. Inclusion was limited to newly diagnosed ANA, defined as the following: (1) continuous enrollment during a 2-year look back period and 6-year study period from index (first) date of ANA diagnosis; (2) diagnosis by an ophthalmologist or optometrist and record of gonioscopy; and (3) no history of intraocular pressure (IOP)-lowering drops, laser peripheral iridotomy (LPI), or intraocular surgery.Cox proportional hazards models were developed to assess factors associated with diagnostic conversion, defined as a change in ICD code from ANA to PACG.New diagnosis of PACG within the 6-year study period recorded after an index diagnosis of ANA.Among 3985 patients meeting inclusion criteria, 459 (11.52%) had detected diagnostic conversion to PACG within the study period. The conversion rate was stable at 3.54% per year after the first 6 months of ANA diagnosis. In the Cox proportional hazards model, age70 years and early (within 6 months of ANA diagnosis) need for LPI or IOP-lowering drops were positively associated with diagnostic conversion (hazard ratio [HR]1.59; P0.02). Cataract surgery at any time and late (after 6 months of ANA diagnosis) need for IOP-lowering drops appeared protective against diagnostic conversion (HR0.46; P0.004).Annual risk of diagnostic conversion from ANA to PACG is relatively low overall; elderly patients are at higher risk whereas patients receiving cataract surgery are at lower risk. The utility of long-term monitoring seems low for most patients with ANA, highlighting the need for improved clinical methods to identify patients at higher risk for PACG.