Clock position-based iris bow configuration after laser peripheral iridotomy in Chinese angle closure eyes: a swept...

To determine how many measurements should be evaluated to determine the iris bow and evaluate changes of iris bow at 12 clock positions after LPI in primary angle closure eyes.

A total of 93 primary angle closure eyes in 93 Chinese patients were enrolled. Anterior iris bowing was evaluated at 12 clock positions and 4 clock positions (3, 6, 9, and 12 o'clock) before, 1 week and 3 months after LPI using swept source optical coherence tomography.

At baseline, almost all of the eyes exhibited an iris bow when measured using 12 clock positions, consistent with results obtained from measurements at 4 clock positions (Cronbach's alpha = 0.99). LPI caused a relative unified change in all of the clock positions (Cronbach's alpha = 0.91) except the LPI site. After LPI, there was no significant difference between 12 and 4 clock position measurements for the iris bow (both p > 0.05), with ~34.1% vs. 33% of the patients remained iris bow at 1 week and 34% vs. 31.9% of the patients remained iris bow at 3 months. However, the coexisting iris bow configuration was more common when measured using 4 clock positions (16.5% vs. 3.3% at 1 week and 25.5% vs. 10.6% at 3 months).

There was excellent consistency when measuring the iris bow at 4 or 12 clock positions. LPI caused a relatively unified iris bow change at 12 clock positions, and a single LPI relieved only ~2/3 of the iris bow configurations.