Increase in anterior chamber angle depth after topical pilocarpine measured by spectral domain optical coherence tomography: A possible additional indicator for laser peripheral iridotomy in primary angle-closure suspects in an opportunistic set-up

Purpose: Indication of laser peripheral iridotomy (LPI) is often conjectural due to dependency on gonioscopy and strict dichotomous classification of occludability. Indentation gonioscopy is the gold standard but is under-utilized for various reasons. The prevalence of primary angle closure disease (PACD) in eastern India is 1.5-1.9%, with a 22% five-year progression rate. Many angle closure patients may go blind without timely diagnosis and iridotomy. General ophthalmologists need alternate, validated methods for diagnoses. Pilocarpine eye drop causes miosis, and flattens the iris, producing angle changes detectable by spectral domain optical coherence tomography (SD-OCT). We hypothesized that the amount of angle change may be a suitable indicator for iridotomy. Methods: Our prospective cross-sectional single-masked observational study evaluated pilocarpine-induced changes in angle parameters detected by SD-OCT. Out of 372 patients enrolled, 273 patients (539 eyes) remained, with a mean age of 48.6 years (SD = 10.36). All eyes were graded by the Van Herick (VH) method, gonioscopy, and anterior segment (AS) SD-OCT and reassessed after pilocarpine drops. Results: The sensitivity and specificity of tomography measurements against gonioscopy grades were 61% and 85%, respectively. The receiver operating characteristic (ROC) curve was 0.85. Pilocarpine-induced angle widening was significant in gonioscopically narrower angles. Low Van Herick grades (217 eyes), narrow gonioscopy grades (238 eyes), and a narrow OCT angle value (165 eyes) were candidates for iridotomy. Conclusion: Our study results showed that pilocarpine-induced angle widening detected by SD-OCT could be a strong objective indicator for LPI.