Anterior segment morphology after laser iridotomy in primary angle closure suspects.

PURPOSE: To evaluate and compare the changes in anterior segment parameters in primary angle closure suspects before and after laser peripheral iridotomy and intrasession repeatability of measurements before laser iridotomy as assessed by Scheimpflug-Placido disc topographer.

METHODS: Before laser iridotomy, 56 eyes of 56 primary angle closure suspect patients underwent anterior segment analysis with the Sirius Scheimpflug-Placido disc topographer system using glaucoma analysis mode, which was repeated a week after iridotomy. Anterior segment parameters such as central anterior chamber depth, central corneal thickness, anterior chamber volume and iridocorneal angle were analysed before and after laser iridotomy and compared with paired t-test. Three consecutive scans were obtained to assess the intrasession repeatability of measurements before iridotomy by a single examiner and intraclass correlation co-efficient was calculated. Multivariate regression analysis was performed to evaluate the predictors associated with iridocorneal angle narrowing.

RESULTS: Intraclass correlation co-efficient values ranged from 0.982 for anterior chamber volume to 0.998 for the iridocorneal angle. After laser iridotomy, mean central anterior chamber depth increased from 2.14 ± 0.29 mm to 2.21 ± 0.28 mm (p = 0.04), mean anterior chamber volume increased from 96.2 ± 16.98 mm3 to 98.14 ± 15.87 mm3 (p < 0.0001) and mean iridocorneal angle widened from 33.38 ± 3.96° to 34.82 ± 4.27° (p = 0.01), compared with pre-iridotomy status. There was no change in central corneal thickness, intraocular pressure or pupil diameter. Multivariate regression analysis model showed that at one week after iridotomy, iridocorneal angle opening was positively correlated with age (β = 0.773, p = 0.005) and anterior chamber volume (β = 1.308, p < 0.0001).

CONCLUSIONS: Laser peripheral iridotomy induces significant changes in the 3-D anterior segment morphology in primary angle closure suspect patients. The Scheimpflug-Placido disc topographer provides reproducible measurements of the iridocorneal angle and other parameters measured and hence, may become clinically useful for non-invasive detection of potentially occludable angles. Predictors of iridocorneal angle widening after iridotomy were older age and anterior chamber volume.