Detection Of Angle-closure In Caucasians By Sequential Testing With Three Non-contact Methods

Abstract

Purpose: : To evaluate the performance of three non-contact methods for detection of narrow angles (NAs) in relatives of patients known to have angle closure.

Methods: : A hospital-based clinic was set up to examine index patients and their relatives for evidence of angle closure requiring treatment. Gonioscopic evidence of NAs, defined as Shaffer grade 0 or 1 in ≥ 2 quadrants, was the reference standard. In a prospective cross-sectional study, gonioscopy, limbal chamber depth (LCD) estimation, IOLMaster, and anterior segment optical coherence tomography (ASOCT) were performed on all subjects. Angle metrics included angle opening distance at 500μm (AOD500) and trabecular iris surface area at 750μm (TISA750) on ASOCT. Results were analyzed as if tests were performed in a sequential approach. Areas under receiver operating characteristic curves (AUC) were generated for single and combined testing.

Results: : We present findings from 236 phakic family members: 127 first degree and 109 more distant relatives. All participants were Caucasian. There were 130 female patients (55%). NAs were identified in 68 patients (29%), 51 of whom were first degree relatives. LCD estimation achieved an AUC of 0.88 (95% CI 0.83-0.92), comparable to AUC 0.82 (CI 0.76-0.86) for ACD, AUC 0.89 (CI 0.85-0.93) for AOD500, and AUC 0.88 (CI 0.83-0.92) for TISA750. At a fixed specificity of 95%, sensitivities for detecting NAs with one method were 32% for LCD (CI 22-45%; cut-off 5%), 28% for ACD (CI 18-40%; cut-off 2.6mm), 46% for TISA750 (CI 34-58%; cut-off 0.06mm) and 54% for AOD500 (CI 42-67%; cut-off 0.1mm). Combined testing of LCD and IOLMaster ACD (cut-off 25% and 2.6mm respectively) gave 99% specificity but did not improve sensitivity (28%). Best performance of sequential testing was achieved with LCD of 25% followed by TISA₇₅₀ or AOD₅₀₀ (using cut-offs of 0.1mm for either angle metrics). These provided 90-96% specificities and 50-69% sensitivities with positive predictive values of 75-85%, and negative predictive values of 83-88% in our cohort.

Conclusions: : The prevalence of NAs in our study was higher than Caucasian population estimates, especially in first degree relatives of patients with angle-closure. Combined testing that includes ASOCT gives the best combination for screening relatives who would benefit from early detection of NAs.

Keywords: clinical (human) or epidemiologic studies: risk factor assessment • detection • anterior chamber