Plateau iris syndrome: Changes in angle opening associated with dark, light, and pilocarpine administration

PURPOSE: To report changes in angle configuration associated with dark, lig ht, and pilocarpine administration in plat eau iris syndrome. METHOD: In 10 eyes of 10 patients with plateau iris syndrome and persistent narrow angles after patent peripheral Nd:YAG laser iridotomy, ultrasound b iomicroscopy was used to image variations in angle opening, iris thickness, and trabecular-ciliary process distance. Measurements were taken in the da rk, in full room light, and after administration of pilocarpine 2%, RESULTS: Average angle opening distance increased in the light compared wit h the dark (113 +/- 34 mu m vs 22 +/- 34 mu m, P = .0001) and increased fur ther after pilocarpine administration (171 +/- 52 mu m vs 113 +/- 34 mu m, P = .0034). Average iris thickness decreased in the light compared with the dark (338 +/- 34 pm vs 436 +/- 58 mu m, P = .0009) and decreased further a fter pilocarpine administration (253 +/- 48 mu m vs 338 +/- 34 mu m, P = .0 002), Average trabecular meshwork-ciliary process distance measurements wer e smaller than normal and did not change significant ly in the light compar ed with the dark (481 +/- 42 mu m vs 464 +/- 44 mu m, P = .4001) or after p ilocarpine administration compared with Light (451 +/- 61 mu m vs 481 +/- 4 2 mu m, P = .1304). CONCLUSIONS: In plateau iris syndrome, anteriorly Located ciliary processes support the peripheral iris. Changes in angle opening in dark and light ar e solely related to changes in iris thickness. Pilocarpine produces iris th inning and is an effective method of opening the angle. Ultrasound biomicro scopy can be used to perform a darkroom provocative test, which provides in formation on whether the angle anatomically closes in the dark. (Am J Ophth almol 1999;128:288-291. (C) 1999 by Elsevier Science Inc. AIL rights reserv ed.)