title: Effects of intravitreal ropivacaine on retinal thickness and integrity in the guinea pig.
abstract: BACKGROUND
  Retrobulbar anesthesia is widely used for ocular surgery.Ocular complications are possible when retrobulbar anesthesia is accidentally injected intravitreally.
  
  
  OBJECTIVE
  The aim of this study was to determine the relative retinal toxicitiesof ropivacaine hydrochloride, a local anesthetic, using various concentrations in guinea pigs.
  
  
  METHODS
  This randomized, investigator-masked, experimental study wasconducted at the Department of Anesthesiology, Dicle University, Diyarbakir, Turkey. The right eyes of 18 guinea pigs were assigned to 1 of 3 treatment groups: 1%, 0.75%, or 0.5% ropivacaine. The right eye of each animal was injected intravitreally with 0.1 mL of 1%, 0.75%, or 0.5% ropivacaine. The left eye of each animal was injected with a balanced saline solution (control). The guinea pigs were euthanized 7 days after injection, and the retinal structures were examined using light microscopy. The total thickness of each retina was measured using an ocular micrometer.
  
  
  RESULTS
  No histologic abnormalities were observed in the control eyes.Retinal damage of most of the retinal section was seen in the eyes receiving study drug. The eyes injected with 0.5% ropivacaine had a generally intact appearance, with the exception of some atrophy and disorganization. Overall, the eyes injected with 1% ropivacaine had significantly more extensive retinal thinning compared with the eyes injected with 0.75% or 0.5% ropivacaine (both, P < 0.01). In the eyes injected with 0.75% or 1% ropivacaine, disorganization of the structure of the retinal layers and atrophy were noted on histopathology. The mean total thicknesses of the retina were significantly less in all ropivacaine-treated eyes compared with that in the controls (P < 0.001).
  
  
  CONCLUSIONS
  In this small experimental study, ropivacaine had concentration-dependent toxic effects on guinea pig retinas.
authors.affiliation: Department of Anesthesiology, Dicle University, Faculty of Medicine, Diyarbakir, Turkey.
authors.forename: Gonul
authors.initials: G
authors.lastname: Olmez
authors.affiliation: Department of Ophthalmology, Dicle University, Faculty of Medicine,Diyarbakir, Turkey.
authors.forename: Sevin
authors.initials: S
authors.lastname: Soker Cakmak
authors.affiliation: Department of Histology and Embryology, Dicle University,Faculty of Medicine, Diyarbakir, Turkey.
authors.forename: Sevda
authors.initials: S
authors.lastname: Ipek Soker
authors.affiliation: Department of Histology and Embryology, Dicle University,Faculty of Medicine, Diyarbakir, Turkey.
authors.forename: Yusuf
authors.initials: Y
authors.lastname: Nergiz
authors.affiliation: Department of Pathology, State Hospital, Diyarbakir Turkey.
authors.forename: Fethin
authors.initials: F
authors.lastname: Yildiz
keywords: animal; guinea pigs; intravitreal; retina; ropivacaine; toxicity