title: Dorzolamide hydrochloride and visual function in normal eyes.
abstract: OBJECTIVE
  To determine by a pilot study whether standard treatment with the topical carbonic anhydrase inhibitor dorzolamide hydrochloride influences visual function under normal breathing conditions, during carbon dioxide inhalation, or during hyperventilation, and to establish criteria for future larger-scale studies.
  
  
  METHODS
  We enrolled 12 normal subjects into this randomized double-masked placebo-controlled crossover study. Each subject was treated with either dorzolamide 2% or placebo, three times daily, for 4 days. After a 2-week washout period, the alternative topical agent was used under identical testing conditions. On day 2 of each treatment phase, contrast sensitivities to sinusoidal gratings of 1 and 4 cycles per degree (cpd) were assessed. On day 4, mean deviation values from full-threshold 10-2 visual fields were obtained. Three sets of each visual function test were obtained before each treatment phase, and in sequence on each testing day, during normal breathing (baseline), inhalation of carbon dioxide-enriched air, and hyperventilation while intraocular pressure was monitored.
  
  
  RESULTS
  Contrast sensitivity at 4 cpd decreased significantly (P < .01) during carbon dioxide supplementation with placebo but showed no significant change with dorzolamide. The decrease in contrast sensitivity accompanying hyperventilation was attenuated (by nearly 50% at 1 cpd) during dorzolamide treatment. Dorzolamide treatment was associated with higher perimetry mean deviation values under each treatment condition and was statistically significant (P < .05) at baseline.
  
  
  CONCLUSIONS
  Dorzolamide appears to enhance contrast sensitivity in normal subjects during physiologic hypercapnia and hypocapnia at 4 and 1 cpd, respectively. Also, under normal breathing conditions, dorzolamide therapy increases perimetric light sensitivity.
authors.affiliation: Department of Ophthalmology, University of Texas Health Science Center, San Antonio, USA. sponsel@uthscsa.edu
authors.forename: W E
authors.initials: WE
authors.lastname: Sponsel
authors.forename: J
authors.initials: J
authors.lastname: Harrison
authors.forename: W R
authors.initials: WR
authors.lastname: Elliott
authors.forename: Y
authors.initials: Y
authors.lastname: Trigo
authors.forename: J
authors.initials: J
authors.lastname: Kavanagh
authors.forename: A
authors.initials: A
authors.lastname: Harris
mesh_terms: D000328:Adult; D002257:Carbonic Anhydrase Inhibitors / Q000008:administration & dosage*; D015350:Contrast Sensitivity / Q000187:drug effects / Q000502:physiology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D016857:Hypocapnia / Q000503:physiopathology; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D009883:Ophthalmic Solutions; D010865:Pilot Projects; D013449:Sulfonamides / Q000008:administration & dosage*; D013876:Thiophenes / Q000008:administration & dosage*; D058609:Visual Field Tests; D014794:Visual Fields / Q000187:drug effects / Q000502:physiology*
chemical_list: D002257:Carbonic Anhydrase Inhibitors; D009883:Ophthalmic Solutions; D013449:Sulfonamides; D013876:Thiophenes; C062765:dorzolamide