A 10-year follow-up to determine the effect of YAG laser iridotomy on the natural history of pigment dispersion syndrome: a randomized clinical trial.

IMPORTANCE Prospective long-term analyses of the role of drug-induced mydriasis and laser peripheral iridotomy (LPI) are needed to identify and manage the eyes of patients with pigment dispersion syndrome (PDS) at risk for progressing to ocular hypertension. OBJECTIVE To assess the 10-year incidence of increased intraocular pressure (IOP) in the 2 eyes of patients with PDS, with 1 eye that underwent LPI and the other that did not. DESIGN, SETTING, AND PARTICIPANTS In a randomized clinical trial in the glaucoma research unit at the University Hospital of Parma, Italy, 72 patients with PDS underwent phenylephrine testing. Of these 72 patients, 29 (58 eyes) tested positive for succeeding IOP elevation, and 43 (59 eyes) tested negative. For the 29 high-risk patients (all in both eyes), one eye was randomly assigned to LPI, and the fellow eye was left untreated. For the 43 low-risk patients, the affected eyes were left untreated. MAIN OUTCOMES AND MEASURES An IOP elevation of 5 mm Hg or higher vs baseline (daily phasing) was considered to be a significant increase (ie, an event). RESULTS In the high-risk group, 3 of 21 eyes that underwent LPI (14.3%) and 13 of 21 untreated eyes (61.9%) showed an increase in IOP of 5 mm Hg or higher during the follow-up period; 4 of 35 low-risk eyes (11.4%) showed a similar increase. Event-free mean (SD) time was 7.99 (0.43) years for high-risk treated eyes, 3.89 (0.68) years for high-risk untreated eyes, and 7.16 (0.23) years for low-risk eyes. The log-rank test showed the following: P < .001 for treated high-risk eyes vs untreated high-risk eyes, P = .74 for treated high-risk eyes vs low-risk eyes, and P < .001 for untreated high-risk eyes vs low-risk eyes. CONCLUSIONS AND RELEVANCE At the end of the 10-year follow-up, (1) approximately one-third of the whole PDS patient population showed an IOP increase of 5 mm Hg or higher in at least 1 eye; (2) phenylephrine testing identified eyes at high risk for developing IOP elevation; and (3) LPI, when performed on high-risk eyes, reduced the rate of IOP elevation to the same level as the low-risk eyes. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01053416.