title: Effect of brimonidine on corneal thickness.
abstract: OBJECTIVE
  Brimonidine, an alpha-2 adrenoceptor agonist, 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 has alpha-2 adrenoceptors, there are only few studies available on the impact brimonidine has on the cornea.
  
  
  METHODS
  Twenty healthy test persons (12 female and 8 male subjects)-mean age about 33 years (22 to 38 years)-were tested in a double-blind, prospective, randomized study. Intraocular pressure as well as epithelial, stromal, and endothelial thickness was measured before, at 25 days while, and at 5 days after administration of brimonidine 0.1% eye drops twice daily. To check the impact of this medication, placebo (proper solution of preservative) eye drops were administered to the other eye twice daily.
  
  
  RESULTS
  Administration of brimonidine 0.1% resulted in a reduction of intraocular pressure from an initial value of 14 to 9 mmHg after 5 days (P=0.001) as well as an increase in total corneal thickness from 556 μm from the time of the baseline examination to 578 μm (P=0.001), an increase of epithelial thickness from 58 to 66 μm (P<0.001), and stromal thickness from 488 to 502 μm (P=0.008) after 2 days each. Another 2 days later, total corneal thickness was 559 μm (P=0.276), epithelial thickness 56 μm (P=0.561), and stromal thickness 493 μm (P=0.315), which means that the values had returned more or less toward the initial values measured. In contrast, endothelial thickness did not vary following administration of brimonidine 0.1% (P=0.965). With treatment with brimonidine 0.1%, mean intraocular pressure in thin corneas (<556 μm) was lower than in the thick corneas (>556 μm, P=0.018).
  
  
  CONCLUSIONS
  Topical administration of brimonidine 0.1% results in a reversible increase in corneal thickness. The question whether this increase is of clinical significance and whether it is the result of epithelial and/or endothelial receptor stimulation cannot be finally answered at the present time.
authors.affiliation: Department of Ophthalmology, University of Tuebingen, Tuebingen, Germany. matthias.grueb@web.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Grueb
authors.forename: Joerg
authors.initials: J
authors.lastname: Mielke
authors.forename: Jens Martin
authors.initials: JM
authors.lastname: Rohrbach
authors.forename: Torsten
authors.initials: T
authors.lastname: Schlote
mesh_terms: D060433:Administration, Ophthalmic; D058647:Adrenergic alpha-2 Receptor Agonists / Q000494:pharmacology*; D000328:Adult; D000959:Antihypertensive Agents / Q000494:pharmacology*; D000068438:Brimonidine Tartrate; D003315:Cornea / Q000187:drug effects* / Q000378:metabolism; D004311:Double-Blind Method; D019573:Epithelium, Corneal / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D011446:Prospective Studies; D011810:Quinoxalines / Q000494:pharmacology*; D013997:Time Factors; D055815:Young Adult
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D000959:Antihypertensive Agents; D011810:Quinoxalines; D000068438:Brimonidine Tartrate