Increase in iris-lens contact after laser iridotomy for pupillary block angle closure

PURPOSE: To quantitate changes in anterior ocular segment anatomy after laser iridotomy for pupillary block angle closure. METHODS: We prospectively performed ultrasound biomicroscopy and A-scan biometry in 13 eyes of 13 consecutive untreated patients with relative pupillary block and appositional angle closure, without peripheral anterior synechiae on indentation gonioscopy. A radial, perpendicular image in the horizontal temporal meridian was obtained with ultrasound biomicroscopy before and one week after laser iridotomy in each eye. RESULTS: Mean age of the 13 patients was 69.3 +/- 1.8 (S.E.) years, mean refractive error was +1.37 +/- 0.39 diopters, and mean axial length was 22.54 +/- 0.20 mm. In 13 eyes, before and after laser iridotomy measurements of angle-opening distance (0.11 +/- 0.02 vs. 0.18 +/- 0.02 mm) (P = .0004; paired t test), angle aperture (8.3 +/- 1.3 vs 18.6 +/- 2.8 degrees) (P = .0003) and iris-lens contact distance (0.58 +/- 0.06 vs 1.18 +/- 0.14 mm) (P = .0003) were greater postoperatively, but anterior chamber depth was unchanged (P = .7). CONCLUSIONS: Flattening of the iris after laser iridotomy for pupillary block causes an increase in iris-lens contact. The change in angle configuration after iridotomy results more from an alteration in aqueous pressure gradients across the iris rather than from posterior lens movement.