Plateau iris configuration in eyes with narrow-angle: an ultrasound biomicroscopic study

To investigate, through ultrasound biomicroscopy images, the presence of plateau iris configuration in eyes with narrow-angle from patients with open-angle glaucoma and in eyes with previous acute primary angle-closure and compare the biometric features of eyes with plateau iris configuration with those of normal eyes.

Ultrasound biomicroscopic images from 196 patients with open-angle glaucoma and narrow-angle and 32 patients with acute primary angle-closure were retrospectively analyzed. The inclusion and specific criteria for the diagnosis of plateau iris configuration was the presence of an anterior positioning of the ciliary processes, supporting the peripheral iris so that it was parallel to the trabecular meshwork; the iris root had a steep rise from its insertion point, followed by a downward angulation from the corneoscleral wall; presence of a central flat iris plane; an absent (complete plateau iris configuration) or partially absent (incomplete plateau iris configuration) ciliary sulcus. The ultrasound biomicroscopic parameters were compared between complete and incomplete plateau iris configuration. The same parameters of both groups were compared with those of normal eyes. The following measurements were performed: anterior chamber depth; angle opening distance at 500 microm from the scleral spur; peripheral iris thickness at 500 microm from the scleral spur; iris-ciliary process distance; trabecular-ciliary process distance and angle recess area.

Plateau iris configuration was found in 33 eyes of 20 (10.2%) out of 196 patients with open-angle glaucoma and narrow-angle and in 4 eyes of 2 (6.3%) out of 32 patients with acute primary angleclosure. Seventeen (77.3%) patients with plateau iris configuration were female and 5 (22.7%) male. Twenty-three (62.2%) out of 37 eyes had complete plateau iris configuration, and 14 (37.8%) had incomplete plateau iris configuration. Complete and incomplete plateau iris configuration presented similar biometric features with the exception of the iris-ciliary process distance. All plateau iris configuration eyes showed biometric parameters completely different from those of normal eyes except for peripheral iris thickness at 500 microm from the scleral spur.

Plateau iris configuration was present in 10.2% of patients with open-angle glaucoma and narrow-angle and in 6.3% of patients with acute primary angle-closure. Biometric features were similar in eyes with complete and incomplete plateau iris configuration with the exception of iris-ciliary process distance. Compared to normal eyes, all plateau iris configuration eyes showed biometric parameters completely different except for peripheral iris thickness at 500 microm from the scleral spur.