title: Comparison of ophthalmic measurements obtained via high-frequency ultrasound imaging in four species of snakes.
abstract: OBJECTIVE
  To measure the dimensions of the eyes of living snakes by use of high-frequency ultrasound imaging and correlate those measurements with age, length, and weight. Animals-14 clinically normal snakes.
  
  
  METHODS
  Species, age, length, weight, and horizontal spectacle diameter were recorded, and each snake underwent physical and ophthalmic examinations; ultrasonographic examination of both eyes was performed by use of a commercially available ultrasound unit and a 50-MHz transducer. Ultrasonographic measurements included spectacle thickness, subspectacular space depth, corneal thickness, anterior chamber depth, lens thickness, vitreous cavity depth, and globe length. All measurements were made along the visual axis.
  
  
  RESULTS
  2 corn snakes, 5 California king snakes, 1 gopher snake, and 6 ball pythons were examined. There were no significant differences within or between the species with regard to mean spectacle thickness, corneal thickness, or subspectacular space depth. However, mean horizontal spectacle diameter, anterior chamber depth, and axial globe length differed among the 4 species; for each measurement, ball pythons had significantly larger values than California king snakes.
  
  
  CONCLUSIONS
  Spectacle thickness, subspectacular space depth, and corneal thickness were similar among the species of snake examined and did not vary significantly with age, length, or weight. Measurements of these dimensions can potentially serve as baseline values to evaluate snakes of these species with a retained spectacle, subspectacular abscess, or subspectacular fluid accumulation. Anterior chamber depth and axial length appeared variable among species, but axial length did not vary with age, length, or weight in the species studied.
authors.affiliation: Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Hollingsworth
authors.forename: Bradford J
authors.initials: BJ
authors.lastname: Holmberg
authors.forename: Anneliese
authors.initials: A
authors.lastname: Strunk
authors.forename: Alicia D
authors.initials: AD
authors.lastname: Oakley
authors.forename: Leann M
authors.initials: LM
authors.lastname: Sickafoose
authors.forename: Philip H
authors.initials: PH
authors.lastname: Kass
mesh_terms: D000818:Animals; D049628:Body Size; D001835:Body Weight; D017821:Boidae / Q000502:physiology; D005123:Eye / Q000000981:diagnostic imaging*; D009799:Ocular Physiological Phenomena; D012016:Reference Values; D012911:Snakes / Q000145:classification / Q000502:physiology*; D013045:Species Specificity; D014463:Ultrasonography / Q000662:veterinary