title: The effect of 1% tropicamide-induced mydriasis and cycloplegia on spherical refraction of the adult horse.
abstract: OBJECTIVE
  To determine the effects of tropicamide 1% on the refractive state of the adult equine globe and identify the most appropriate time period (in relation to mydriasis) to perform streak retinoscopy.
  
  
  METHODS
  Eight university-owned mares of various ages and breeds.
  
  
  METHODS
  Topical tropicamide 1% was applied to one randomly selected eye from each of the horses to induce mydriasis and cycloplegia. The contralateral eyes served as controls. Streak retinoscopy and pupillometry were performed prior to, and every 5 min after tropicamide 1% installation for 90 min.
  
  
  RESULTS
  All values are expressed as mean ± SD. Both horizontal (2.8 ± 0.74 mm) and vertical (7.3 ± 1.29 mm) mean pupil diameters increased significantly (P < 0.04) in the treatment eyes compared with the control eyes (horizontal [0.48 ± 0.85 mm] and vertical [1.06 ± 1.31 mm] pupil diameter). No significant differences in the refractive states of the treatment (horizontal: +0.25 ± 0.43 D and vertical: +0.41 ± 0.37 D) or control (horizontal: +0.34 ± 0.39 D and vertical: +0.41 ± 0.37 D) eyes were identified at any time point. Three of the eight treatment eyes demonstrated blurry or reversing streak reflexes during streak retinoscopy evaluation following the application of topical tropicamide 1%.
  
  
  CONCLUSIONS
  While these reflexes did not significantly influence streak retinoscopy results, their presence may subjectively influence a novice retinoscopist's ability to obtain accurate results. Therefore, optimal streak retinoscopy results may be obtained prior to, or 40- to 45-min following the application of topical tropicamide 1%, once near-maximal dilation has been achieved.
authors: Department of Clinical Sciences, North Carolina State University, Raleigh, NC, USA.
authors: Richard J
authors: RJ
authors: McMullen
authors: Michael G
authors: MG
authors: Davidson
authors: Brian C
authors: BC
authors: Gilger
mesh_terms: D000818:Animals; D005123:Eye / Q000187:drug effects*; D005260:Female; D006736:Horses; D018727:Muscarinic Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D015878:Mydriasis / Q000139:chemically induced / Q000662:veterinary*; D014331:Tropicamide / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D018727:Muscarinic Antagonists; D014331:Tropicamide
keywords: cycloplegia; equine ophthalmology; mydriasis; pupillometry; streak retinoscopy; tropicamide