Visual disturbance: where do I look?

Visual disturbances often signal serious ophthalmic disease. Comprehensive general medical and ophthalmic histories are most helpful. Information about the animal's vision, based on its performance in familiar and unfamiliar environments, should be obtained from the owner. As bilateral involvement and visual disturbances are often associated with systemic diseases, a complete physical examination is indicated. The ophthalmic examination consists of a series of diagnostic procedures to isolate and define the ophthalmic disorder. Several clinical tests can be performed easily in the examination room, including the light-induced pupillary reflex, the dazzle or photic reflex, the menace reflex, the obstacle course test and, if indicated, the flash electroretinogram, the visual evoked response and, recently, the pattern electroretinogram. Ophthalmic diseases that produce visual disturbances in dogs often affect the cornea, aqueous pathways, lens and ocular fundus; in cats, they usually affect the uveal tract and are associated with serious systemic diseases. Orbital diseases are not usually associated with visual disturbance unless the optic nerve is involved. Corneal diseases and cataract formation that involve the visual axis and pupillary aperture often cause visual disturbance. Inflammations of the Iris and ciliary body can produce both acute and long-term visual disturbance and even blindness. Diseases of the retina and optic nerve usually present as visual disturbances in the absence of pain.