title: Comparison of Cytotoxic Effects on Rabbit Corneal Endothelium between Preservative-free and Preservative-containing Dorzolamide/timolol.
abstract: OBJECTIVE
  To evaluate and compare the toxic effects of eyedrops containing a fixed combination of 2.0% dorzolamide and 0.5% maleate timolol with or without preservatives on rabbit corneal endothelium.
  
  
  METHODS
  This study was performed with 22 eyes of New Zealand white rabbits. Dorzolamide/timolol eyedrops with preservative (Cosopt group) or without preservative (Cosopt-S group) were diluted with a balanced salt solution at a 1 : 1 ratio. We injected 0.1 mL of diluted Cosopt into the anterior chamber of left eyes and an equal volume of diluted Cosopt-S into the anterior chamber of right eyes. Corneal thickness, corneal haze, and conjunctival injection were measured before and 24 hours after treatment. Endothelial damage was compared between both eyes by vital staining (alizarin red/trypan blue staining), live/dead cell assay, TUNEL assay, and scanning electron microscopy.
  
  
  RESULTS
  Corneal endothelial damage was severe in the Cosopt group. Cosopt-treated eyes exhibited remarkable corneal edema and prominent apoptosis of endothelial cells. In addition, the live/dead cell assay revealed many dead cells in the endothelium, and scanning electron microscopy analysis showed that corneal endothelial cells exhibited a partial loss of microvilli on the surface as well as extensive destruction of intercellular junctions. However, in the Cosopt-S group, corneal edema was mild and the damage to the corneal endothelium was minimal.
  
  
  CONCLUSIONS
  The main cause of corneal endothelial toxicity was due to the preservative in the dorzolamide/timolol fixed combination eyedrops, and not the active ingredient. Thus, it appears to be safer to use preservative-free eyedrops during the early postoperative period.
authors.affiliation: Department of Ophthalmology, Korea University College of Medicine, Seoul, Korea.
authors.forename: Junki
authors.initials: J
authors.lastname: Kwon
authors.affiliation: Department of Ophthalmology, Korea University College of Medicine, Seoul, Korea.
authors.forename: Jeong Hwa
authors.initials: JH
authors.lastname: Heo
authors.affiliation: Department of Ophthalmology, Korea University College of Medicine, Seoul, Korea.
authors.forename: Hyo Myung
authors.initials: HM
authors.lastname: Kim
authors.affiliation: Department of Ophthalmology, Korea University College of Medicine, Seoul, Korea.
authors.forename: Jong Suk
authors.initials: JS
authors.lastname: Song
mesh_terms: D000818:Animals; D000867:Anterior Chamber / Q000187:drug effects; D017209:Apoptosis; D015715:Corneal Edema / Q000139:chemically induced / Q000473:pathology*; D004195:Disease Models, Animal; D004338:Drug Combinations; D004728:Endothelium, Corneal / Q000187:drug effects / Q000473:pathology*; D020287:In Situ Nick-End Labeling; D009883:Ophthalmic Solutions; D011817:Rabbits; D013449:Sulfonamides / Q000008:administration & dosage / Q000633:toxicity*; D013876:Thiophenes / Q000008:administration & dosage / Q000633:toxicity*; D013999:Timolol / Q000008:administration & dosage / Q000633:toxicity*
chemical_list: D004338:Drug Combinations; D009883:Ophthalmic Solutions; D013449:Sulfonamides; D013876:Thiophenes; C479140:dorzolamide-timolol combination; D013999:Timolol
keywords: Cytotoxicity; Endothelium; Ophthalmic solutions; Rabbits