Remote Tonometry Identifies Significant Variability in the Timing of Intraocular Pressure Response to Topical Medication Change

Purpose To characterize the time to maximum intraocular pressure (IOP) change after stopping and restarting topical prostaglandin analog (PGA) treatment using remote tonometry. Design Prospective single-site observational study. Subjects Patients with primary open-angle glaucoma or ocular hypertension treated with ≥ 4 weeks of PGA monotherapy, in whom the managing ophthalmologist ordered medication washout to assess the necessity of continued topical therapy. Methods Patients used a rebound home tonometer to obtain ≥4 daily measurements across 3 periods: “Baseline” (1 week while continuing PGA), “Washout” (4 weeks off therapy), and “Restart” (4 weeks while restarting PGA). Exponential decay functions were used to model IOP from “Baseline” through “Washout” and then from end of “Washout” through “Restart” to determine the time to 90% of maximum IOP change (plateau, T 90% %). We evaluated the variation in T 90% using multilevel models to account for the inclusion of both eyes from individual subjects. Main Outcome Measures T 90% for “Washout” and “Restart” Results 20 subjects (34 eyes) successfully recorded multiple daily eye measurements for the 9-week study period. Mean (SD) IOPs during the “Baseline”, “Washout”, and “Restart” periods were 15.6 (4.2) mmHg, 17.3 (5.0) mmHg, and 15.9 (4.4) mmHg, respectively. “Baseline” and “Restart” IOPs were significantly lower than “Washout” IOP (p < 0.001). T 90% was significantly longer and more variable among subjects during Washout (median: 18.5 days; IQR 6.0-32.1 days) compared to Restart (2.2 days; 1.3-4.1 days, p < 0.001). Conclusions Using remote tonometry, we identified a significantly longer T 90% after stopping PGA drops than when they were restarted. The ranges of time to reach the IOP plateau were wide, often exceeding the standardized 4-week washout, and are relevant to clinical assessment of routine treatment effects and determination of accurate washout periods for clinical research studies.