Laser peripheral iridotomy for dark-induced angle closure changes: A proof-of-concept study

This is a proof-of-concept study of laser peripheral iridotomy (LPI) outcomes in phakic eyes with "dark-induced angle closure (AC) changes" (DACC). DACC was diagnosed gonioscopically in the dark as presence of traces of iridotrabecular contact (ITC) and/or a Shaffer angle≤20°.

We evaluated phakic adult outpatients. We recorded the retinal nerve fiber layer (RNFL) thickness, intraocular pressure (IOP), and performed gonioscopy in the dark to assess ITC traces and the Shaffer angle value. LPI was performed in both eyes using a YAG laser.

We assessed the first treated eye of 114 patients (mean±standard deviation) age: 59.6±11.6; Caucasian: 82%, normal IOP without glaucoma: 92%; average or deep limbal anterior chamber: 78.1%. At baseline, the mean IOP was 15.6±3.4mmHg. The RNFL thickness was above the normal minimum value in 103 eyes, with, nonetheless, qualitative abnormalities/asymmetry in 107 eyes. Gonioscopy in the dark showed traces of ITC in all eyes and a Shaffer angle≤20° around the 6 o'clock meridian in 54 (47%). In all eyes, during the laser procedure, as soon as the iridotomy became wide enough, the aqueous humor from the posterior chamber burst forward into the anterior chamber, immediately deepening it. At the 12-month visit, the mean IOP had decreased by 1.7±2.0mmHg (P<0.001), and the mean RNFL had increased by 0.42±2.2μm (P=0.045). None of the 38 patients with a history of morning headaches experienced them after bilateral LPI.

LPI provided favorable outcomes in eyes with DACC, suggesting DACC to be a clinical entity of early-stage AC. If confirmed in controlled studies, this approach might help to prevent AC and AC glaucoma.