Restoring sensitivity to timolol after long-term drift in primary open-angle glaucoma.

In a prospective randomized single-masked study lasting 6 months, 39 eyes with primary open-angle glaucoma showing a long-term drift with 0.5% timolol were put on a "timolol holiday" lasting 30 or 60 days. Twenty-three of them were enrolled with dipivefrin 0.1% twice daily during the holiday. When timolol therapy was restored, the dipivefrin-treated group showed a more pronounced decrease of intraocular pressure (IOP) (8.2 +/- 1.5), whereas the IOP decrease in the nondipivefrin-treated group was lower (3.9 +/- 1.2) and of shorter duration (less than 60 days). Among the dipivefrin-treated group, the response to timolol was more prolonged in the eyes treated for 60 days: the IOP of these eyes was less than 23 mmHg throughout the follow-up.