Effect of timolol on central corneal thickness

Purpose: Timolol is an effective and safe medication that is widely used in glaucoma treatment. Although it is known that it is quickly taken up by the cornea following topical administration and that the cornea exhibits beta-adrenergic receptors, there are few studies available on the clinical impact of timolol on central corneal thickness (CCT). Methods: Twenty healthy subjects were tested in a double-blind, prospective, and randomized study. Intraocular pressure (IOP) and CCT were measured before and during administration of timolol 0.5% eyedrops over 28 days. Results: Administration of timolol 0.5% resulted in a reduction of IOP from an initial value of 16 +/- 2 mm Hg to 13 +/- 0 mm Hg (p<0.001, R-2 = 0.7033) as well as an increase in CCT from 555 +/- 11 mu m from the time of the baseline examination to 567 +/- 9 mu m (p = 0.005, R-2 = 0.8754), an increase of epithelial thickness from 53 +/- 2 mu m to 59 +/- 3 mu m (p<0.001, R-2 = 0.5063), and an increase of stromal thickness from 494 +/- 4 mu m to 498 +/- 9 mu m (p = 0.045, R-2 = 0.4352) after 9 days each. From day 10 on, a decrease in CCT (R-2 = 0.6164), epithelial thickness (R-2 = 0.2216), and stromal thickness (R-2 = 0.2092) was observed. At the end, the values had returned toward the initial values measured (CCT 553 +/- 8 mu m, p = 0.391; epithelial thickness, 50 +/- 2 mu m, p = 0.214; and stromal thickness, 493 +/- 8 mu m, p = 0.483). In contrast, endothelial thickness did not vary following administration of timolol 0.5% (p = 0.727, R-2 = 0.009). Conclusions: Topical administration of timolol 0.5% results in a reversible increase in CCT. These modest changes are unlikely to influence tonometry or clinical decision-making.