What are corneal ulcers?
A corneal ulcer is an open sore of the cornea, which is the transparent dome-shaped layer that covers the front of the eye.
The cornea protects the eye from dust, germs, and other debris, as well as reshaping and focusing light rays onto the retina; it consists of five layers.
- Bowman’s membrane
- Descemet’s membrane
Tears bathe the cornea to keep it nourished and prevent it from drying out.
Causes of corneal ulcers in cats
Damage to the outer layer of the cornea due to scratches (corneal abrasion). Erosion of the cornea typically involves more than one layer and can occur for several reasons.
- Injury or trauma (such as rubbing an itchy eye, foreign body)
- Infection (fungal, bacterial or viral infection especially feline herpes)
- Chemical irritants
- Eyelid/eyelash disorders
- Dry eye (lack of tear production)
- Foreign body
Secondary bacterial infection can develop once the cornea has become damaged, which further complicates the problem. In severe cases, the ulcer can progress through the layers of the outer eye and cause the eyeball to rupture.
What are the signs of corneal ulcers in cats?
- Pain, due to the rich supply of nerves, the deeper the injury, the greater the pain
- Ocular discharge
- Sensitivity to light
- Excessive tear production (epiphora)
- Eyelid spasms (blepharospasm)
- Cloudiness of the cornea
Do not attempt to treat the ulcer at home and never use human eye drops on a cat unless a veterinarian has instructed you to do so.
How are corneal ulcers diagnosed?
The veterinarian will perform a physical examination and a thorough ophthalmic (eye) evaluation. Large ulcers may be visible to the naked eye. Fluorescein stain may be necessary to detect small ulcers, this test involves placing a dark orange dye called fluorescein into the eye and using a penlight or special cobalt blue filtered light which can help to identify damage to the cornea.
It is also important for the veterinarian to determine the cause. If the cat is experiencing flu-like symptoms such as a runny nose, sneezing, fever, then a presumptive diagnosis of “cat flu” (herpes or calicivirus) can be made.
- Scratches will show up on the fluorescein stain.
- A Schirmer tear test will be necessary to check for dry eye.
What is the treatment for corneal ulcers?
The goal of treatment is to address the underlying cause and help the cornea heal by controlling inflammation, pain as well as preventing secondary infection. This may include drops to stimulate the production of tears, supportive care and/or anti-fungal medications, surgery to correct eyelid abnormalities.
Atropine is a medication that causes the pupil to dilate, which can help to relieve pain from ciliary muscle spasms, which are muscles responsible for dilation and constriction of the pupils. Cats with dilated pupils will be sensitive to light, therefore they should be provided access to a dark room to retreat to.
Trifluridine, Ganciclovir, Famciclovir, Idoxuridine and Vidarabine are topical and ocular antiviral medications that will be prescribed for cats with feline herpes. Antibiotics will be prescribed for cats with bacterial infections.
Serious cases may need to be protected by temporarily suturing the eyelid shut (tarsorrhaphy).
Once treatment commences, the ulcer should heal within 5-7 days. During this time you may notice red streaks in the eye (neovascularisation), due to blood vessels that have formed to help with the repair of the ulcer. They will eventually go away.