What is the retina and why is it important?
The retina is a thin layer of light sensitive cells in the back of the eye. These cells, called photoreceptors, take all the visual input coming into the eye and convert it to a signal that can be transmitted through the optic nerve to the brain for interpretation. It is one of the primary structures needed for vision.
What is retinal detachment?
Retinal detachment occurs when some (partial detachment) or all (complete detachment) of the thin layer of light sensitive cells peel away from the back of the eye.
The retina is firmly attached to the eye in only two spots: around the optic nerve and the area of the eyeball behind the lens. Everywhere else, the retina is kept in place by interdigitations. Think of this like wallpaper glued on drywall. When fluid gets between the layers of cells - like water underneath wallpaper - the retina will peel away from the inner surface of the eye.
When retinal detachment occurs, the light sensitive cells lose access to the blood vessels that supply them with oxygen and nutrients. This causes vision loss in any area of the retina that has been detached.
What causes retinal detachment?
Retinal detachment in cats is often caused by fluid buildup behind the retina, most commonly from high blood pressure (systemic hypertension). High blood pressure can be a result of kidney disease, hyperthyroidism or it can have no apparent cause (idiopathic). Other causes of retinal detachment include traumatic tearing of the retina, uveitis (inflammation inside the eye), glaucoma, certain infectious diseases, and cancer.
What are the signs of retinal detachment?
The most noticeable sign in cats is sudden blindness. Be aware if your cat starts bumping into furniture or not moving around your home as much as normal. Behavioral signs can be subtle. You may notice their pupils are also abnormally large (dilated), even in bright light. If the condition only affects one eye, you may notice they have different sized pupils.
How is retinal detachment diagnosed?
Retinal detachment can often be seen using an ophthalmoscope or special lens to examine the back of the eye. A typical detached retina resembles boat sails billowing toward the observer, held in place by its permanent attachments. Partial detachments can be more difficult to see as they can cause small slightly raised areas with decreased reflectivity (light shining back at the observer). Your veterinarian may see small areas of bleeding at the site of the detachment. If the condition has been occurring for a while, there may be abnormal blood vessels.
Sometimes the front of the eye has become too opaque to see the retina. In these cases, an ophthalmologist may diagnose a detached retina using ultrasound.
Part of diagnosis will be trying to determine what caused the retina to detach, as treating the underlying cause is needed for the best outcome. Your veterinarian will want to run tests including a complete blood count (CBC), biochemistry profile, thyroid evaluation, and blood pressure assessment. If infectious disease, uveitis, or glaucoma is suspected, your veterinarian will recommend more specific testing for these conditions, such as testing for feline leukemia virus and assessing their intra-ocular pressure (pressure within the eye).
What is the treatment for retinal detachment?
The longer the retina is detached, the less oxygen and nutrients it receives. Rapid treatment is crucial to prevent the cells from dying and to return your cat’s vision. Treatment depends on the findings of the diagnostic tests and the specific conditions identified by your veterinarian.
"Rapid treatment is crucial to prevent the cells from dying and to return your cat’s vision."
If your cat is hypertensive, they will be started on medication such as amlodipine or telmisartan (Semintra®) to reduce their blood pressure. These drugs may be combined with other medications such as ACE-inhibitors (FortekorÒ, EnacardÒ) if needed. In rare cases, cats may need injectable medication and in-hospital monitoring to bring down their blood pressure to a level where it can be controlled with at-home medication.
Your veterinarian may recommend emergency referral to a veterinary ophthalmologist for further assessment and treatment. If there is a tear in the retina, surgery may be necessary to repair it or prevent it from getting worse. If a tumor is identified, the ophthalmologist may recommend removal of your cat’s eye (enucleation) to remove the cancerous tissue and make your cat more comfortable.
Will my cat need to have more testing?
Because it is crucial to treat the underlying cause as quickly as possible, your veterinarian will recommend regular follow-up visits and tests to assess your cat’s response to the prescribed treatment. This ensures that if the treatment is not working as quickly as needed, a new plan can be put in place without delay.
Will my cat’s vision return to normal?
If retinal detachment is caught and treated early, cats can typically get their normal vision back, especially if the underlying cause is high blood pressure (hypertension). However, if retinal detachment goes untreated for even a few days, a cat’s vision may be permanently affected.
