Nd:YAG laser iridotomy in pigment dispersion syndrome: an ultrasound biomicroscopic study

Ultrasound biomicroscopy was used to study the shape of the iris and the iridolenticular contact in pigment dispersion syndrome (PDS) eyes, to compare them with matched normal eyes, and to assess the morphological effects of laser iridotomy in PDS eyes.

50 eyes of 50 patients suffering from PDS (group 1), and 15 normal eyes of 15 subjects matched for age and refraction (group 2), were studied by ultrasound biomicroscopy (UBM, Humphrey-Zeiss). Nd:YAG laser iridotomy was proposed to the 30 PDS patients with concave iris and 18 underwent the treatment.

The iris was concave in 27 eyes in group 1, and three more eyes showed a concave iris during accommodation. Among normals, iris concavity was present in two eyes. The height of the iris convexity was -0.15 (0.24) mm (range -0.65 to +0.21), in the eyes of group 1, whereas it was +0.07 (0.10) mm (range -0.21 to +0.16) in group 2 (p < 0.0012). Group 1 had greater iridolenticular contact than group 2: 1.55 (0.78) mm (range 0.30-2.88) and 1.07 (0.61) (range 0.30-2.50; p = 0.0304). After laser iridotomy, only one eye still had a concave iris. Pre- and post-treatment deflections were -0.35 (0.18) mm (range -0.61 to -0.05) and +0.01 (0.06) mm (range -0.12 to +0.17), respectively (p < 0.0001). Pre- and post-treatment iridolenticular contact was 2.10 (0.65) mm (range 0.70-2.88) and 0.93 (0.38) mm (range 0.4-1.75), respectively (p < 0.0001). After laser iridotomy, the treated irises were flatter than normal (p = 0.0207), whereas the iridolenticular contact was not significantly different.

Laser iridotomy can restore a normal iris shape and iridolenticular contact in eyes suffering from PDS.