Effect of timolol on central corneal thickness and endothelial cell density

Background: The measurement of corneal thickness plays an increasing role in glaucoma screening and diagnosis. The influence of a variety of drugs on corneal thickness is well established. Especially for antiglaucomateous drugs this effect seems to be important. However, little is known about the influence of beta receptor antagonists on corneal thickness. The aim of this study was to provide evidence of the effect of timolol on central corneal thickness and endothelial cell density. Materials and Methods: Ten healthy volunteers (five women and five men) with a mean age of 29 years (range 25 to 56 years) were examined in a double-blind, prospective and randomised pilot study. Intraocular pressure, corneal thickness and endothelial cell density was estimated before as well as fifteen minutes, 24, 48, 72 and 96 hours after application of timolol 0.5% eye drops twice daily. The partner eye received sodium hyaluronate eye drops twice daily and served as a control. Results: The application of timolol showed a decrease of intraocular pressure from initially 12 mmHg to 9 mmHg after four days (p = 0,0188) as well as an increase of corneal thickness from 537 mu m to 557 mu m after four days (p=0,0659). There was no change of intraocular pressure (p=0,9935) or corneal thickness (p=0,9998) in the control eyes. There was also no effect of timolol (p = 0,2782) or sodium hyaluronate (p 0,1940) on endothelial cell density. Conclusions: The study provides evidence of the influence of beta receptor antagonists on corneal thickness. This effect may be caused by receptor mediated influences on corneal ion and fluid transport. Further studies are needed to show if the increase of corneal thickness after application of topical timolol has clinical importance.