Overview of Blindness in Dogs
Blindness is the loss of vision in both eyes. Vision loss may arise from disorders of the structures that receive and process the image within the eye or from disorders of the visual pathways that transmit and further process the image within the brain.
Acute (sudden) blindness occurs when vision is lost in both eyes simultaneously. The actual onset of blindness may be difficult to pinpoint because dogs’ senses of hearing and smell can often compensate for a decrease in vision. When one eye is blind, most dogs act and behave normally. The owner may not realize vision has been lost in one eye, until such time as it is decreased in the other eye. If an acute loss of sight occurs in the other eye from a disease or injury, then the dog may seem to go acutely blind.
At times the realization that the pet is blind only occurs when a change in the environment confuses the pet. Animals that slowly lose their vision memorize their surroundings, and if those surroundings are altered, then the behavioral changes they exhibit may make the owner conclude that the animal has gone blind suddenly. In actuality, the blind dog starts bumping into things only because the environment has changed.
Blindness in some pets may not be observed until vision is lost in eyes that had minimal function previously. Causes of blindness include severe corneal disease, anterior and/or posterior uveitis, cataracts (white opacity of the lens), retinal inflammation and infection, retinal detachment, glaucoma (sustained elevated pressure within the eye), disease of the optic nerve (nerve that connects the eye to the brain) and visual pathways, and diseases of the occipital cortex (visual center of the brain).
What to Watch For
Bumping into objects
Inability to find food and water dishes
Inattentive behavior, excessive sleeping
Easily startled, fearful behavior
Loss of normal play or interactive behaviors
Becoming lost in the yard or certain areas of the house
Diagnosis of Blindness in Dogs
Diagnostic tests are essential in determining the exact cause of the blindness. Tests may include:
Complete physical examination
Complete ophthalmic examination, including direct and indirect ophthalmoscopy, pupillary light reflex testing, slit-lamp biomicroscopy, tonometry, Schirmer tear testing, navigation of the pet through an obstacle course, visual tracking and visual placing tests, and fluorescein staining of the cornea.
Complete neurologic examination
Other Diagnostic Tests
Complete blood count (CBC) and serum tests via blood samples
Blood pressure testing
Visually evoked response test
Specific serologic tests
Corneal and conjunctival cell samples for cytology
Cerebral spinal fluid tap
Specialized imaging tests of the eye and skull, such as ultrasound examinations, CAT scans or MRI
Treatment of Blindness in Dogs
Successful treatment depends on obtaining an accurate diagnosis.
Pets with recent onset of blindness should be evaluated by your veterinarian as soon as possible. Minimize stress and injury by confining your pet to a safe area until the cause of the problem is determined. Place barriers across staircases, over hot tubs and around pools, and restrict activity on balconies if your pet could fall through the guardrails. Do not allow dogs to run free.
Establish a known location for the food and water bowls and guide your pet to them if necessary; do not change his environment. Use a harness or leash to walk your dog for better guidance and control.
Do not allow your pet to scratch or rub his eye if it is painful, as this may cause further damage to the eye. Use an Elizabethan collar if necessary.
In-Depth Information on Blindness in Dogs
Therapy for a blind pet always depends first on establishing the correct diagnosis. There are numerous possible causes for blindness, and it is essential to identify the specific cause to initiate appropriate treatment.
Causes of Canine Blindness
Blindness can be caused by many different conditions, including:
Severe entropion, which is inversion or an inward rolling of the eyelid margins, or heavy facial folds and brows – especially a problem in the shar-pei and chow-chow breeds
Keratoconjunctivitis sicca (dry eye syndrome) with resultant corneal scarring, blood vessel in-growth, and pigment deposition on the corneal surface
Corneal endothelial degeneration, which is degenerative disease of the inner lining of the cornea. Degeneration results in an opaque, bluish appearance of the cornea.
Severe pannus, also called chronic superficial keratitis, that results in dramatic blood vessel infiltration and scarring of the cornea in German shepherd and German shepherd-cross dogs
Severe uveitis due to an immune-mediated disease; a systemic bacterial, viral, protozoal or fungal infection; or a tumor
Hyphema (blood in the anterior chamber) secondary to ocular trauma, a blood clotting disorder or systemic hypertension (high blood pressure)
Cataract (dense opacity in the lens) formation
Lens luxation (displacement) with secondary glaucoma
Glaucoma, which is sustained elevated pressures within the eye due to inadequate fluid drainage from the eye, resulting in damage to the optic nerve
Progressive retinal degeneration, an inherited condition in many purebred dogs
Chorioretinitis (inflammation of the choroid and retina) secondary to an immune-mediated disease; a bacterial, viral, protozoal, fungal or parasitic infection; tumor
Retinal detachment secondary to a congenital malformation of the retina; a bacterial, viral, protozoal, fungal or parasitic infection; systemic hypertension; tumor
Retinal degeneration from nutritional deficiencies of vitamin A and/or vitamin E (rare)
Sudden acquired retinal degeneration (SARD), a disease of unknown cause that results in complete dysfunction of the retinal photoreceptors (rods and cones)
Congenital underdevelopment of the optic nerves (very rare)
Encephalitis (inflammation of the brain) or meningoencephalitis (inflammation of the brain and the membranes that cover it) due to a viral, protozoal, fungal or bacterial infection, or from a granulomatous type of inflammation
Neoplasia (tumor) involving the optic chiasm (location in the brain where both optic nerves meet and cross) or optic pathways with in the brain
Neoplasia involving the occipital cortex (visual center of the brain)
Hydrocephalus (fluid accumulation within the skull compressing the brain)
Hypoxia (inadequate oxygen supply to the brain) resulting in permanent brain injury
Cerebral vascular infarct (occlusion of a blood vessel in the brain) resulting in brain injury
Head trauma with edema and hemorrhage
Traumatic avulsion (tearing away)of the optic nerves from the optic chiasm or from behind the eye
Hepatic encephalopathy (severe liver disease causing abnormal neurologic signs including disorientation and stupor) or severe hypoglycemia (low blood sugar) imitating vision loss
Certain toxins, such as lead poisoning