Ophthalmic manifestations can occur with inherited, infectious, degenerative, parasitic, toxic, nutritional and neoplastic disorders in animals. Often, ophthalmic examinations can assist in timely identification of the systemic disorder. Diseases affecting the vascular and nervous systems may also show ocular manifestations. Animals with bilateral intraocular disease should be carefully evaluated for systemic diseases.
In dogs, ophthalmic diseases, such as retinal dysplasia, microphthalmia, and cataracts, have been associated with dwarfism, albinism Pigmentary Abnormalities in Animals Many associations between skin and coat color and developmental anomalies have been recorded in domestic animals. Some of the associations with hypotrichosis are discussed under hereditary alopecia... read more , and merle coloration. Infectious diseases often involve the uveal tract and present as iridocyclitis, choroiditis, and panuveitis. They may be caused by viruses (distemper, infectious hepatitis), rickettsial diseases Rickettsial Diseases (ehrlichiosis and Rocky Mountain spotted fever), bacteria (Brucella canis and Borrelia burgdorferi), fungi (Blastomyces, Coccidioides, Histoplasma, Cryptococcus, and Aspergillus), protozoa (Toxoplasma, Neospora, Leishmania, and Hepatozoon), algae (Prototheca), or parasites (Dirofilaria, Toxocara, and Diptera species). Metabolic diseases associated with eye diseases in the dog include diabetes mellitus Diabetes Mellitus in Dogs and Cats Diabetes mellitus is a common endocrine disease in dogs and cats, occurring in about 1 of every 300 patients. Clinical signs reflect hyperglycemia with resultant glycosuria. Diagnosis is made... read more (cataract formation), hypocalcemia Hypocalcemia in Dogs and Cats Hypocalcemia causes the major clinical manifestations of hypoparathyroidism by increasing the excitability of both the central and peripheral nervous systems. Peripheral neuromuscular signs... read more (cataracts), hyperadrenocorticism Cushing Syndrome (Hyperadrenocorticism) Cushing syndrome refers to any cause of elevated cortisol concentrations. Pituitary-dependent hyperadrenocorticism (PDH; Cushing disease) is the most common form of hyperadrenocorticism and... read more (corneal disease, cataracts, and lipemia retinalis), and hypothyroidism Hypothyroidism in Animals Hypothyroidism is thyroid hormone deficiency. It is diagnosed by clinical features such as lethargy, weight gain, obesity, haircoat changes, and low serum thyroid hormone concentrations. Management... read more (keratoconjunctivitis sicca [KCS], intraocular hemorrhages from increased systemic blood pressure, and lipemia retinalis [hyperlipidemia]). Blood and vascular disorders may present as intraocular hemorrhage, retinal detachment, secondary glaucoma, and papilledema. Metastatic neoplasms, such as lymphosarcoma, can present as persistent uveitis, overt intraocular masses, intraocular hemorrhage, secondary glaucoma, and/or retinal detachment. Systemic hypertension often results in retinal hemorrhage and/or serous retinal detachments. With appropriate diagnosis and treatment, these retinal lesions can resolve and vision can be retained or returned.
In cats, systemic diseases frequently affect the eye and associated structures. Eyelid inflammation may be associated with systemic Demodex cati and D gatoi, Notoedres cati (scabies), ringworm Dermatophytosis in Dogs and Cats Dermatophytosis (ringworm) is typically a superficial skin infection. It affects a wide range of animals, and several of the causative fungi also cause zoonotic infections. In otherwise healthy... read more , and immune-mediated skin diseases. The pathogens that commonly cause infectious diseases of cats—eg, feline herpesvirus 1 (FHV-1), Chlamydia, and Mycoplasma—frequently present as acute and recurrent conjunctivitis. FHV-1 is also associated with ulcerative and stromal keratitis, proliferative keratoconjunctivitis, corneal sequestrum, corneal symblepharon, and KCS. Feline infectious peritonitis Feline Infectious Peritonitis (FIP), toxoplasmosis Toxoplasmosis in Animals Toxoplasmosis is an important zoonotic protozoal infection worldwide. All homoeothermic animal species may be infected. Infection is generally asymptomatic and chronic in immunocompetent individuals... read more , feline immunodeficiency virus (FIV), and feline leukemia virus Feline Leukemia Virus often present as anterior and posterior uveitis, chronic uveitis, retinal detachment, and secondary glaucoma. Acute vision loss with intraocular hemorrhage and retinal detachment in older cats may be secondary to systemic hypertension and is often associated with chronic renal failure or hyperthyroidism. Resolution of intraocular hemorrhages, repair of retinal detachment, and possible restoration of vision depend on the successful lowering of blood pressure to normal levels; this is most often achieved by treatment with amlodapine.
In horses, systemic infectious diseases, such as adenovirus in immunodeficient Arabian foals, equine influenza Equine Influenza Equine influenza is highly contagious and spreads rapidly among naive horses. Horses 1–5 yr old are the most susceptible to infection. Orthomyxovirus A/equine-2 was first recognized in 1963... read more , strangles Strangles in Horses Strangles is an infectious, contagious disease of Equidae characterized by abscessation of the lymphoid tissue of the upper respiratory tract. The causative organism, Streptococcus equi equi... read more (Streptococcus equi), Rhodococcus equi infection, leptospirosis Leptospirosis in Horses Leptospirosis is caused by spirochete bacteria in the genus Leptospira. In horses, serovars Pomona and Grippotyphosa are the most common in North America. Clinical findings include abortion... read more , Lyme disease Lyme Borreliosis in Animals Lyme borreliosis is a vector-borne zoonotic disease transmitted by ticks infected with spirochetal bacteria belonging to the genus Borrelia. Affected dogs typically present with intermittent... read more (Borrelia burgdorferi), and salmonellosis Salmonellosis in Horses Salmonellosis is one of the most commonly diagnosed infectious causes of diarrhea in adult horses. Clinical manifestations range from no abnormal clinical signs (subclinical carrier) to acute... read more , may present as conjunctivitis, anterior uveitis, or posterior uveitis. Ophthalmic onchocerciasis can present with anterior and posterior uveitis, peripapillary chorioretinitis, keratitis, keratoconjunctivitis, or lateral conjunctival vitiligo; treatment is systemic ivermectin. Habronemiasis ("summer sores") presents with inflammatory conjunctival masses of the periocular area (especially the medial canthus) associated with the aberrant migration of larvae of Habronema muscae, H microstoma, and Draschia megastoma. Treatment is usually to administer systemic ivermectin or moxidectin, debride the lesions, institute topical and environmental fly control, and protect the skin from the moisture of tear drainage with a barrier ointment.
In cattle, microphthalmia, cataracts, retinal dysplasia, and retinal detachments are associated with hydrocephalus Congenital and Inherited Cerebral Disorders in Animals Anencephaly means that the brain is largely absent at birth. It is a rare disorder but is seen sporadically in calves; the cause is unknown. Because the pituitary gland may also be absent, prolonged... read more and in utero infection of calves with bovine viral diarrhea Bovine Viral Diarrhea . The same ophthalmic defects occur in lambs affected in utero with bluetongue Bluetongue in Ruminants Bluetongue is a viral disease of ruminants worldwide. Clinical signs in sheep result from vascular endothelial damage, including edema of the muzzle, tongue, and coronary bands. Diagnosis is... read more virus. Vitamin A deficiency causes microphthalmia in piglets, and blindness and optic nerve hypoplasia in calves. Vitamin A deficiency in adult or growing cattle results in night blindness, mydriasis, and eventually total blindness. Ophthalmoscopic abnormalities include papilledema, retinal degeneration, and optic nerve atrophy. Vitamin A supplementation may restore vision in animals with night blindness only. Lymphosarcoma in cattle may present as bilateral progressive exophthalmos. Many infectious diseases, such as rhinotracheitis, malignant catarrhal fever Malignant Catarrhal Fever in Animals Malignant catarrhal fever is a severe, often fatal, lymphoproliferative disease of artiodactyls caused by ruminant gammaherpesviruses. Clinical signs include fever, oral and nasal erosions,... read more , thromboembolic meningoencephalitis Meningitis, Encephalitis, and Encephalomyelitis in Animals Meningitis, encephalitis, and encephalomyelitis are terms used to describe inflammatory conditions of the meninges, brain, or brain and spinal cord, respectively. These inflammatory processes... read more , and neonatal septicemia, may present with conjunctivitis or anterior or posterior uveitis. Intoxications such as male fern poisoning (Dryopteris filix), bracken fern poisoning (Pteridium aquilinum) in sheep, coumarin poisoning (sweet clover poisoning) in cattle, and phenothiazine toxicosis in cattle present with clinical signs of blindness from retinal degeneration, intraocular hemorrhage, or corneal edema. (Also see Toxicology Introduction Toxicology Introduction .)