What is the cornea?
This is the clear, outermost layer of the eyeball.
What may cause an ulcer, or erosion, of the cornea?
- Foreign bodies: such as grass seeds, thorns, sand, grass, sticks
- Scratches from another animal: beware of cat scratches, especially to puppies’ eyes
- Irritation from a chemical: such as shampoo
- Self-trauma: if scratching or rubbing at the head due to another reason
- Rough injury: such as running into a bush
- Infections: viral infections such as herpes virus in cats, bacterial infections can delay healing of corneal ulcers
What are the symptoms of a corneal ulcer?
The conjunctiva (the pink tissue around the eyeball inside the lids) will often swell up and look redder, compared with the normal eye. The eye is often watering or gunky, and squinting. Your pet will most likely be rubbing at the eye with their paw, or on the ground.
How is a corneal ulcer diagnosed?
A veterinarian will use a stain called Fluorescein in your pet’s eye. This stain will not stick to normal healthy cornea, but it will stick to the underlying tissue. Therefore, if there is an ulcer, or erosion, on the cornea it will show up bright green under UV light.
Your vet will often then use a drop of local anaesthetic, to help them explore the eye, especially under the third eyelid, to ensure there isn’t a foreign body present.
Sometimes, your pet may be too painful or wriggly, meaning we can’t get a good look at their eyes. On those occasions we will consider sedating them so we can examine them properly.
How do we treat a corneal ulcer?
Treatment involves removing foreign bodies if present (sometimes this requires a full anaesthetic), keeping the cornea moist (with drops 2-3 times a day), and preventing infection (with ointment, and sometimes systemic antibiotics as well). If the eye is particularly painful, we will prescribe pain relief medication.
If the eye is showing signs of uveitis (deeper structures of the eye are affected) we may prescribe atropine to dilate the pupil as well.
Your pet will often come home with a raft of medication. It is important you follow the instructions carefully. If you are having trouble administering the eye drops, please call the clinic to discuss.
If your pet is rubbing at the eye, we will suggest using a head cone to prevent further trauma to the cornea.
Please ensure you keep to the requested follow up appointments. We need to ensure the ulcer is resolving.
What if the corneal ulcer does not heal?
Sometimes corneal ulcers don’t heal despite medication. There are a few reasons why:
- Melting ulcer: sometimes an infection gets involved which actually melts the cornea, giving it a gooey tan coloured appearance. The eye is at risk of rupture in these situations. We will want to take samples to culture the organism and will have to be aggressive with our treatment. Sometimes we take a sample of your pet’s blood and use the serum directly on to the eye. Your pet may need to be hospitilised in these situations.
- Indolent ulcer: Boxers and poodles are notorious for these, but they can happen in any breed. The ulcer won’t heal because the edges aren’t stuck down on to the underlying tissue. We often need to do surgery to remove these edges and carefully “roughen” the area to encourage healing. Usually, we sew the third eyelid shut and leave it like that for up to 2 weeks, to protect the eye while it is healing. These pets MUST wear a head cone at all times, to prevent them scratching at the eye and undoing all our good work.
- A cat with chronic herpesvirus infection: Many cats are carriers of Feline Herpesvirus (FHV-1), but most of them don’t show any symptoms as adults apart from a mildly runny nose or occasional sneeze at times of stress. However, there is a small subset of cats (particularly Persians) who develop corneal sequestrums in response to the virus. A sequestrum is an area of the cornea which dies and turns black/dark brown. This area usually needs to be surgically removed and a tissue graft applied. They can sometimes be managed topically over a long period of time. This can become frustrating for pet and owner.
With careful treatment, most corneal ulcers resolve quickly and without fuss. The most important thing to do is to follow your vet’s instructions and request a revisit if you are concerned.