Ocular disorders of pet mice and rats

Light: An Extrinsic Factor Influencing Animal-based Research

Light is an environmental factor that is extrinsic to animals themselves and that exerts a profound influence on the regulation of circadian, neurohormonal, metabolic, and neurobehavioral systems of all animals, including research animals. These widespread biologic effects of light are mediated by distinct photoreceptors-rods and cones that comprise the conventional visual system and melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs) of the nonvisual system that interact with the rods and cones. The rods and cones of the visual system, along with the ipRGCs of the nonvisual system, are species distinct in terms of opsins and opsin concentrations and interact with one another to provide vision and regulate circadian rhythms of neurohormonal and neurobehavioral responses to light. Here, we review a brief history of lighting technologies, the nature of light and circadian rhythms, our present understanding of mammalian photoreception, and current industry practices and standards. We also consider the implications of light for vivarium measurement, production, and technological application and provide simple recommendations on artificial lighting for use by regulatory authorities, lighting manufacturers, designers, engineers, researchers, and research animal care staff that ensure best practices for optimizing animal health and well-being and, ultimately, improving scientific outcomes.

Vivarium Lighting as an Important Extrinsic Factor Influencing Animal-based Research

Light is an extrinsic factor that exerts widespread influence on the regulation of circadian, physiologic, hormonal, metabolic, and behavioral systems of all animals, including those used in research. These wide-ranging biologic effects of light are mediated by distinct photoreceptors, the melanopsin-containing intrinsically photosensitive retinal ganglion cells of the nonvisual system, which interact with the rods and cones of the conventional visual system. Here, we review the nature of light and circadian rhythms, current industry practices and standards, and our present understanding of the neurophysiology of the visual and nonvisual systems. We also consider the implications of this extrinsic factor for vivarium measurement, production, and technological application of light, and provide simple recommendations on artificial lighting for use by regulatory authorities, lighting manufacturers, designers, engineers, researchers, and research animal care staff that ensure best practices for optimizing animal health and wellbeing and, ultimately, improving scientific outcomes.

Ophthalmologic Diseases of Small Mammals

Ophthalmic examination of small mammals follows the same principles as in other species. Reference values for tear production and intraocular pressure are provided. Conjunctivitis and epiphora is common in rabbits. Numerous infectious organisms have been isolated from rabbits with conjunctivitis. Dental disease can be a cause for conjunctivitis in rabbits. Treatment consists of topical and oral antimicrobial agents and irrigation of the nasolacrimal system. Underlying dental disease needs to be addressed. Ulcerative keratitis, corneal dystrophy, membranous occlusion of the cornea and eosinophilic keratitis are described. Encephalitozoon cuniculi can cause phacoclastic uveitis in rabbits. A break in the anterior lens capsule exposes lens protein with subsequent anterior uveitis and cataract formation. Cataract surgery can be performed to remove the affected lens. Glaucoma is inherited as an autosomal recessive trait in rabbits. Orbital disease in rabbits may be associated with dental disease. Treatment is often difficult due to the caseous nature of the abscessed material. The most common ophthalmic diseases seen in ferrets include conjunctivitis, corneal endothelial cell degeneration, cataract formation, retinal degeneration and orbital disease. Ophthalmic diseases in guinea pigs include conjunctivitis, dermoids, cataract and osseous metaplasia of the mesectodermal trabecular meshwork. Exophthalmos may be related to dental disease in guinea pigs and chinchillas. Chromodacryorrhea is seen in rats and mice associated with inflammation of the Harderian gland. Sialodacryoadenitis virus is a highly contagious virus that may cause exophthalmos, epiphora and keratoconjunctivitis. Ammonia vapors from soiled bedding can cause keratoconjunctivitis in hamsters.

Incorporating Laboratory Animal Science into Responsible Biomedical Research

Biomedical research has made great strides in the past century leading to rapid advances in human life expectancy, all derived from improved understanding, prevention, and treatment of many diseases and conditions. Research involving laboratory animals has played a significant role in this medical progress. However, there continues to be controversy surrounding the use of animals in research, and animal models have been questioned regarding their relevance to human conditions. While research fraud and questionable research practices could potentially contribute to this problem, we argue that a relative ignorance of laboratory animal science has contributed to the “uncontrolled vivarium experiment” that runs parallel to the more controlled scientific experiment. Several variables are discussed, including husbandry, animal environment, social housing, and more, that can contribute to this uncontrolled experiment, and that can simultaneously decrease quality of life for rodent test subjects when ignored. An argument is put forward that laboratory animal veterinarians and scientists can and should play an important role in better controlling such variables. Similarly, the laboratory animal veterinarian and scientist should play an important role in responsible science by addressing complex interdisciplinary challenges.

Eye and Associated Glands

The eye is susceptible to adverse toxic effects by direct application, inadvertent ocular contact, or systemic exposure to chemicals or their metabolites. Although the albino rat is a less than ideal model for ocular toxicity studies, it has gained popularity for specific applications and may be the first species in which the ocular toxicity of a systemically administered xenobiotic becomes evident. This chapter reviews the embryology, anatomy, and physiology of the eye and associated glands and describes common nonneoplastic and neoplastic lesions encountered in laboratory rats.

Common Emergencies in Small Rodents, Hedgehogs, and Sugar Gliders

Small exotic mammal pets such as rats, mice, hamsters, gerbils, degus, hedgehogs, and sugar gliders are becoming more popular. Because these animals are prone to a variety of health problems, and require specialized husbandry care to remain healthy, they may present to emergency hospitals in critical condition. This article provides a basic overview of common emergency presentations of these species.

Eye Removal Surgeries in Exotic Pets

This article covers considerations and techniques of eye removal surgeries in exotic pets. After issues including surgical indications, anesthesia, patient preparation, and instrumentation are explored, surgical techniques are described. Enucleation/exenteration and modified evisceration are discussed, with species-specific nuances of small mammals, birds, reptiles, snakes, amphibians, and fish highlighted.