Water-drinking test in primary angle-closure suspect before and after laser peripheral iridotomy

Background: This study aimed to investigate whether performing a laser peripheral iridotomy in primary angle-closure suspects had an effect on the intraocular pressure response during the water-drinking test. Design: Prospective study in a hospital setting. Participants: Primary angle-closure suspects scheduled for a laser peripheral iridotomy. Methods: Primary angle-closure suspects were evaluated before the laser peripheral iridotomy and 2weeks after. On each visit, subjects underwent the water-drinking test. Intraocular pressure was measured every 15min within a 1-h period. Main Outcome Measures: Intraocular pressure fluctuations during the water drinking test. Results: Twenty patients were enrolled. The mean age was 58.1years (±10.2 SD), predominantly female (n=14, 70%). Average intraocular pressure range (maximum-minimum) during the water-drinking test increased significantly from 2.6±1.1mmHg before the laser peripheral iridotomy to 3.5±1.5mmHg after (P=0.04). The mean difference between peak and last intraocular pressure measurements increased after the laser peripheral iridotomy was performed, from 2.5mmHg (±1.27 SD) to 3.3mmHg (±1.66 SD), (P=0.057). There was no change in mean peak intraocular pressure (maximum-baseline) before and after the laser peripheral iridotomy (P=0.87). Conclusions: Primary angle-closure suspects who underwent the water-drinking test had a slightly more pronounced recovery of intraocular pressure after the laser peripheral iridotomy was performed, which may be attributed to increase in the area of exposed trabecular meshwork following treatment. Differences in intraocular pressure curves before and after laser peripheral iridotomy were minimal, and therefore, the water-drinking test had limited value as a provocative test in this patient population.