WHAT IS A CORNEAL ULCER?

• The loss of corneal epithelium with or without loss of varying amounts of the underlying corneal stroma (i.e. a scratch or sore on the clear surface of the eye that can sometimes go deeper than just the top layer).
• 3 main categories:

1. Simple corneal ulcer – an acute loss of the epithelial layers usually due to trauma and they are usually not infected (like a superficial scratch)
2. Complex corneal ulcer – an acute or chronic loss of epithelial and/or stromal layers of the cornea due to trauma and/or infection (a deeper scratch or sore)
3. Indolent/refractory corneal ulcer/Superficial Chronic Corneal Epithelial Defect (SCCED) – a superficial ulcer resulting from failure of epithelial adhesion to the corneal basement membrane and stroma (a superficial scratch/sore that doesn’t heal with conventional treatment)

CAUSES AND RISK FACTORS

• Trauma (scratches, play, cat’s claws, sticks/branches)
• Foreign bodies (grass awns, thorns)
• Keratoconjunctivitis sicca (dry eye)
• Brachycephalic breeds are predisposed
• Eyelid conformation abnormalities (entropion/ectropion, distichiasis, trichiasis, ectopic cilia, lagopthalmos)
• Feline herpesvirus type 1 (FHV-1) – contagious amongst cats

CLINICAL SIGNS

• Painful eye – usually seen with blepharospasm (squinting the eye or holding the eye closed) or rubbing at the eye
• Cloudiness or bluish tinge to the surface of the eye
• Red eye
• Ocular discharge (watery, mucoid or mucopurulent)
• Occasionally with upper respiratory signs in cats, especially those with FHV-1
• With more severe ulcers, you may see “melting” of the cornea which gives the cornea a jelly-like appearance and in some of these cases the cornea can rupture.

DIAGNOSIS

• Corneal ulceration is suspected based on history and a thorough ophthalmic examination.
• The ocular exam usually includes:

1. Tear testing
2. Fluorescein staining
3. Assessment of the cornea for swelling (oedema), blood vessels, pigment etc
4. Determining if there is an underlying cause (abnormal eyelashes, eyelids, growths etc)
5. When infection is suspected, a corneal swab/sample is recommended for culture and susceptibility testing to ensure the correct antibiotic is used if needed.

TREATMENT

1. Simple corneal ulcer:

• Broad-spectrum topical antibiotic drops usually 4 x per day.
• Systemic non-steroidal anti-inflammatory drug (NSAID) for pain relief and to keep inflammation under control (for patients in which this is appropriate).
• Placement of a buster collar to prevent self-trauma to the eye.
• Sometimes topical Morphine drops can be applied for a short period of time to also help relieve pain.
• A lubricant is also advised to keep the eye moist, especially when dry eye could be part of the underlying cause.
• In cats, corneal ulcers are often caused by FHV-1 and an anti-viral eye drop is also advised twice a day (this may become a chronic treatment as the virus can take long to clear and can often flare-up at regular intervals).
• Most simple ulcers will heal with minimal scarring in 5-10 days with appropriate treatment.

2. Complex corneal ulcer:

The above treatments as for simple ulcers but with the addition of:

• Topical serum – if there is evidence of “melting” or deeper layers of the stroma are involved (every 1-4 hours as needed).
• Addition of another antibiotic if needed, used at an increased frequency (every 2 hours for 12-24 hours).
• Oral Doxycycline antibiotic can assist with healing due to its special anti-inflammatory and anti-collagen-breaking properties that help protect the cornea while it heals.
• Hospitalisation at a 24-hour facility is sometimes advised for these patients so that their drops can be given very frequently (even throughout the night) and for close monitoring that the eye is not getting worse.
• If the ulcer is very deep, sometimes surgical intervention is necessary and referral to a specialist ophthalmologist is often advised for these cases.
• Healing can take between 2-8 weeks, and substantial corneal scarring can be expected.

3. Indolent/refractory ulcers/SCCEDs:

• Surgical intervention is necessary for these ulcers, as the abnormal epithelial cells need to be debrided off the cornea and to encourage the new epithelium to “stick” to the basement membrane (this is usually performed at a specialist ophthalmologist facility).
• There are a few procedures which can be performed but a treatment called a “striate keratotomy” is usually the treatment of choice. During a striate keratotomy, small superficial scratches are made and cover the entire corneal surface. This encourages the new healing cells to anchor down and allows the ulcer to close.
• Usually, a contact lense is placed over the cornea after the procedure and this acts like a bandage for the eye.
• An antibiotic, lubricant and NSAID, as well as a buster collar are usually also part of the treatment for an indolent ulcer.
• Most heal with minimal scarring within 2-3 weeks with appropriate treatment (recently French Bulldogs have been shown to take a lot longer to heal properly than is usually described).

IMPORTANT POINTS TO NOTE

• It is very important to have any ulcer seen by your veterinarian.
• They can often start as simple but can quickly become complex if left untreated.
• In severe cases, they could become a threat to your pet’s vision and in worst-case scenarios require the removal of an eye, hence it is imperative that treatment is not delayed.
• Ensure that you take your pet for regular check-ups while their ulcers are being treated so that progress can be assessed and changes to the treatment plan adjusted as needed.

References

Cohn, L. A., & Cote, E. (2019). Clinical Veterinary Advisor. Elsevier.