Cherry eye is a term used to describe the popping out of a tear gland in the eyelid. The condition is uncommon in pet rabbits but needs to be treated by your veterinarian as soon as possible.
What is cherry eye?
Many mammals, like rabbits, have a third eyelid, also known as the nictitating membrane. It is a thin bit of tissue that sits under the lower eyelid. The third eyelid contains a gland that produces 50% of the tears of the eye, called the nictitans gland. This gland is very important for keeping the delicate surface of the eye (cornea) healthy by preventing the eye from drying out, and by flushing away dust and other irritants.
Cherry eye is a common term used to describe prolapse or popping out of the nictitans gland. When this gland pops out from under the protective cover of the eyelid, it appears as a bulging, bright red mass along the inner corner of the lower eyelid.
Why does it occur?
Cherry eye can occur from trauma to the eye, damage from a foreign body in the eye, or from a tumour, but the most common cause is an anatomical abnormality ligament that is supposed to hold the nictitans gland in place.
In some breeds of animals, particularly those with shorter faces, or relatively large eyes the ligament in the third eyelid which is supposed to hold the nictitans gland in place, is abnormally weak. This results in the gland easily popping out from under the lower outer eyelid. Once the gland is out of the protective eyelid covering, it swells, dries out, and becomes red and inflamed. It also cannot function as it is supposed to, and this can cause the eye to dry out. While cherry eye usually occurs in a single eye at a time, animals that are prone to condition will usually have it occur in both eyes.
It should be said that rabbits can temporarily have reddened third eyelids as a result of stress, but this is not cherry eye as it quickly resolves and will not show the persistent bulging characteristic of cherry eye.
How is cherry eye diagnosed and treated?
Once the nictitans gland prolapses/pops out, it needs to be treated by a veterinarian as soon as possible as the eye is prone to getting too dry which risks further complications like corneal ulcers.
The first steps of diagnosis will involve investigating the eye to determine if there are any obvious causes for the condition. This can include looking for foreign bodies, lesions, abscesses or tumours that occupy the orbital space in and around the eye. Your rabbit may need skull x-rays and/or advanced imaging, such as MRI or CT scanning to help make the diagnosis.
In some cases, minor swelling can be reduced with eye drops and if there is infection, antibiotics may be prescribed. Typically, cherry eye is a condition that needs surgical intervention as soon as possible to place the gland back in its normal position. Your rabbit will require general anaesthetic for the procedure. Eye drops may be prescribed after surgery to help the eye recover from irritation.
Once the procedure is complete, the gland usually returns to normal function within 2-3 weeks.