Measurement of the change in angle recess area following laser iridotomy for pupillary block and plateau iris

Purpose. To examine the change in angle anatomy following laser iridotomy (LI) in eyes with relative pupillary block (RPB) or plateau iris configuration (PIC). Methods. Ultrasound biomicroscopy (UBM) and A-scan biometry were performed in each quadrant on 11 eyes of 11 untreated patients with RPB and 4 eyes of 4 patients with PIC before and after LI. PIC was defined on the basis of the absence of a ciliary sulcus on UBM. A perpendicular was drawn from a point on the corneal endothelium 750 μm anterior to scleraspur to the iris surface. The angle recess area (ARA) was defined as the triangle demarcated by this line. Area measurements were achieved for each image using a custom-designed program capable of tracing irregular borders. Results. Age (p=0.15), refractive error (p=0.20), and axial length (p=0.67) were similar between the RPB and PIC groups. The ARA widened following LI in the RPB group (0.06 ± 0.03 vs. 0.10 ± 0.04 mm²; p=0.002, paired t-Test), but not in the PIC group (0.08 ± 0.03 vs. 0.07 ± 0.02 mm²; p=0.68, paired t-Test). Conclusions. Angle widening after LI is typical for RPB but not PIC. UBM is useful in differentiating these two entities and predicting which angles will widen after LI.