Design: Consecutive Creek patients who were newly diagnosed as having EXG or POAG were prospectively investigated; they underwent 24-hour diurnal IOP measurements first without therapy and then 6 months afterward while they were being treated with timolol maleate (0.5%). After matching for age, 38 pairs of patients with these 2 types of glaucoma were compared.

Results: Untreated patients with EXG had significantly higher IOP values for all time points assessed and a greater mean range of IOPs (11.8 mm Hg for EXG vs 7.6 mm Hg for POAG; P less than or equal to.001). Following therapy with timolol maleate (0.5%) given twice daily, patients with EXG had higher IOP values for the measurements that were obtained at 6 and 10 AM, 10 PM, and 2 AM, a higher mean range of IOPs (7.0 mm Hg for EXG vs 5.6 mm Hg for POAG; P=.03), and a higher maximum IOP (mean, 24.9 mm Hg for EXG vs 20.9 mm Hg for POAG; P=.003). The reduction of the range of diurnal variation of TOP was more pronounced in patients with EXG than in patients with POAG (40% vs 26%; P=.04). Twenty-two (58%) of 38 patients with EXG and 20 (53%) of 38 patients with POAG had peak TOP values that were found outside office hours. Only 5 (13%) of the patients with EXG exhibited an IOP of 18 mm Hg or less at all time points compared with 12 (32%) of the patients with POAG (P=.05).

Conclusion: Despite a greater initial TOP reduction in the patients with EXG treated with timolol, a higher IOP and significant fluctuation in the diurnal curve of IOP during the time in which patients received therapy still characterized EXG from POAG.