Diagnostics of retinal diseases in dogs with cataract
Cataract, the lens opacification, is one of the frequent, but not the only, cause of visual impairment and blindness in dogs [1]. Cataracts often accompanied by progressive retinal atrophy - hereditary disease, defining a progressive gradual degeneration of photoreceptors [1, 2]. A lot of dog breeds are affected by hereditary progressive retinal atrophy: miniature poodle, dachshund, golden retriever, Tibetan Terrier and others [1, 3]. Often the opacity of the lens is secondary to the progressive retinal atrophy ("toxic cataract") [2, 3]. Clinical signs of progressive retinal atrophy (PRA) typically include impaired vision in low light conditions, and further, with the progression of the disease - the complete loss of vision [1-4]. In the group of animals considered in this article, the reason for visiting the clinic was lens opacity and visual impairment. This determined the need to differentiate the causes of vision loss in this group of animals. Proper evaluation of retinal function in dogs with cataract is important because the presence of retinal pathology may be exclusion criterion when selecting the patient for phacoemulsification of cataract [2]. For the diagnosis of PRA ophthalmoscopy can be used, and typical changes in are: retinal blood vessels attenuation, hyperrefectivity of tapetal area, depigmentation of non-tapetal area, however, in the animals with cataract in mature and hypermature stages ophthalmoscopy is impossible to performe [2, 4]. In this regard, veterinary ophthalmology requires additional tests and procedures to diagnose retinal pathologies when ophthalmoscopy is not possible. Currently, ophthalmologists have a number of techniques for making the diagnosis in dogs with impaired visual function and cataract (biomicroscopy, tonometry, ophthalmoscopy, ultrasonography of the eyeball, assessment of pupillary light reflex to light with different wavelengths, testing of visual ability, electroretinography) [1, 3, 6]. The aim of the study was to compare the diagnostic value of these methods for the detection of PRA in dogs with cataracts.