The order Rodentia is the largest order of mammals. It contains 2,020 living species placed in 28 families, which is approximately half of all mammalian species. Despite the large number of rodent species, few are owned as pets. Rodents commonly kept as pets are rats, mice, hamsters, gerbils, guinea pigs, and chinchillas.1 Hamsters are one of the most popular pet species among rodents.2 Approximately 1.1 million hamsters are maintained as pets in approximately 0.87 million homes in the United States.3 Ophthalmic examination is a necessary part of a complete routine health assessment for all domestic animals. Systemic diseases can be associated with ocular lesions in all animal species. Recognition of these ocular signs is useful in the diagnosis and treatment of systemic diseases. The assessment of IOP is a crucial component of a complete ophthalmic examination because assessment of IOP can contribute to the diagnosis of severe ocular diseases (eg, glaucoma or uveitis).4 Assessment of IOP could help clinicians to more accurately diagnose ocular and systemic diseases and to more effectively make treatment decisions.
The IOP can be affected by the tone of extraocular muscles, closure of the eyelids, retraction of the retractor bulbi muscle, external pressure, intraocular changes, drugs, curvature and thickness of the cornea, corneal and scleral rigidity, time of day, head and body position, and tear film viscosity.5–8 It is known that IOP is not constant and varies considerably throughout the day. However, the physiologic role of and mechanisms for daily variation are poorly understood.9
The use of certain drugs, such as anesthetics, may cause alterations in IOP. Ketamine is a dissociative drug that can be used as a sole agent for inducing anesthesia or in combination with other agents for inducing and maintaining anesthesia.10 In clinical practice, ketamine-diazepam and ketamine-xylazine combinations have been used for the induction of anesthesia in hamsters.11
In a previous study12 conducted by our research group, reference values for ophthalmic diagnostic tests (including IOP) in clinically normal Syrian hamsters (Mesocricetus auratus) were reported. The purpose of the study reported here was to assess circadian variation in IOP throughout the day in Syrian hamsters, a nocturnal species. We also assessed effects of anesthetic agents on IOP in clinically normal Syrian hamsters.
PSL portable slit lamp, Reichert Inc, Buffalo, NY.
Binocular indirect ophthalmoscope, Welch Allyn Inc, Skaneateles Falls, NY.
Fluorescein Glostrips Nomax Inc, St Louis, Mo.
Zone-Quick, Menicon America Inc, San Mateo, Calif.
TonoVet, Icare, Tiolat, Helsinki, Finland.
Ketamine 10%, Alfasan, Woerden, The Netherlands.
Xylazine 2%, Alfasan, Woerden, The Netherlands.
Zepadic, Caspian Tamin Pharmaceutical Co, Rasht, Iran.
IBM SPSS 20.0 for Windows, IBM Co, Chicago, Ill.
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