Blindness in Cats

Overview of Feline Blindness

Blindness is the loss of vision in both eyes. In cats, 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 cats’ senses of hearing and smell can often compensate for a decrease in vision. When one eye is blind, most cats 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 cat may seem to go acutely blind.

At times the realization that the cat is blind only occurs when a change in the environment confuses the cat. Animals that slowly lose their vision memorize their surroundings, and if those surroundings are altered, then the behavioral changes exhibited by the cat may make the owner conclude that the cat has gone blind suddenly. In actuality, the blind cat starts bumping into things only because the environment has changed.

Blindness in some cats may not be observed until vision is lost in eyes that had minimal function previously. Common causes of either acute or chronic vision loss include severe corneal disease, severe 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

• Occasional clumsiness
• Bumping into objects
• Inability to find food and water dishes
• Inattentive behavior, excessive sleeping
• Easily startled, fearful behavior
• Loss of normal play or hunting behaviors

Diagnosis of Blindness in Cats

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
• Electroretinography
• Visually evoked response test
• Specific serologic tests
• Cerebral spinal fluid tap
• Specialized imaging tests of the eye and skull, such as ultrasound examination, CAT scans or MRI

Treatment of Blindness in Cats

Successful treatment depends on obtaining an accurate diagnosis.

Home Care

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. Restrict activity on balconies if your pet could fall through the guardrails.

Establish a known location for the food and water bowls and guide your pet to them if necessary; do not change his environment.

Do not allow your pet to scratch or rub his eyes if he appears painful, as this may cause further damage to the eye. Use an Elizabethan collar if necessary.

In-depth Information on Blindness in Cats

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 Feline Blindness

Blindness can be caused by many different conditions, including:

• Bilateral uveitis due to a systemic bacterial, viral, protozoal or fungal infection, or from 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), particularly if complicated by cataract development
• Glaucoma, which is sustained elevated pressures within the eye due to inadequate fluid drainage from the eye, resulting in damage to the optic nerve. Glaucoma in the cat is most often secondary to chronic uveitis.
• Chorioretinitis (inflammation of the choroid and retina) secondary to a bacterial, viral, protozoal, fungal or parasitic infection, or to a tumor
• Retinal detachment secondary to systemic hypertension, a posterior segment tumor, or chorioretinitis
• Nutritional retinal degeneration caused by taurine deficiency in the diet
• Progressive retinal degeneration, a rare inherited condition of Abyssinian and certain domestic short-haired cats
• Congenital underdevelopment of the optic nerves (very rare)
• Encephalitis (inflammation of the brain) or meningoencephalitis (inflammation of the brain and the meninges that cover it) due to a viral, protozoal, fungal or bacterial infection
• Neoplasia (tumor) involving the optic chiasm (location in the brain where both optic nerves meet and cross) or the visual pathways within the brain
• Neoplasia involving the occipital cortex (visual center of the brain)
• Hypoxia (inadequate oxygen supply to the brain) resulting in permanent 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) imitating vision loss.

Diagnosis In-depth

Veterinary care should include tests to establish a diagnosis and subsequent treatment. Diagnostic tests are essential in determining the exact cause of the blindness. Tests may include:

• Complete physical examination and history
• 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 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
• Electroretinography to evaluate the electrical responses of the retina to light stimulation
• Visually evoked response test to detect abnormality within the optic nerve or visual center of the brain
• Specific serologic tests to evaluate the cause and identify any related problems
• Specialized imaging tests of the eye and skull, such as ultrasound examinations, MRI (magnetic resonance imaging) or CT (computed tomography) scans
• Cerebral spinal fluid tap to collect a sample of fluid surrounding the spinal cord and brain with a small needle

Treatment In-depth

Successful treatment depends on obtaining an accurate diagnosis.