ADVICE

What is a non-healing corneal ulcer?

The cornea is the transparent structure at the front of the eye that allows light to enter. Traumatic injury, most commonly a scratch or foreign bodies, but also eyelid diseases (entropion), eyelash disease (ectopic cilia or distichiae), infectious agents and dry eye can damage the thin waterproof layer on the surface of the cornea, called epithelium, and expose the underlying tissue, called stroma, to cause an ulcer.

If the ulcer is shallow, then it will usually heal on its own within a few days as the epithelium regenerate from the edges and spread across the defect. However, in some dogs the healing process does not occur because an acellular hyaline layer forms over the exposed stroma, which prevents the epithelial cells from adhering to it. This prevents the epithelial migration across the ulcer which would normally achieve healing. This type of ulcer is superficial and not infected, but will not heal and can persist for many months if left untreated.

What are the signs of an indolent corneal ulcer?

Common signs of a corneal ulcer include:

• The white of the eye has become reddened
• Clear or white discharge from the eye
• Clouding or dullness of the surface of the eye
• Discomfort (blinking more, rubbing, keeping the eye half closed)

Why does an indolent ulcer refuse to heal?

The epithelium at the edges of an indolent ulcer is loose and underrun, unable to ‘stick down’ to the underlining stroma and cover the defect, due to the presence of a hyaline layer. For the indolent ulcer to heal, this non-adherent epithelium together with the hyaline layer need to be removed so that normal healthy epithelium can form and spread across.

What are the treatment options for indolent ulcers?

There are various options for treatment of non-healing ulceration, which aim to remove this hyaline layer:

• Cotton bud debridement under topical anaesthesia. The surface of the eye is debrided with a sterile cotton bud. This treatment has a 50 per cent success rate per procedure and can be repeated every seven to 10 days
• Diamond burr debridement under topical anaesthesia or light sedation. The surface of the eye is debrided with a special instrument called a diamond burr. This treatment has a 85-100 per cent success rate per procedure, and can be repeated every two weeks, but we advise that this is not repeated more than three times in total
• Superficial keratectomy under general anaesthesia. The top layer of the corneal ulcer is removed with a special blade with the aid of a surgical operating microscope. This treatment has 100 per cent success rate with only one treatment, but it is more expensive and requires general anaesthesia.

What happens after the procedure?

When they go home, the pet needs to wear a Buster collar for around a week so that they cannot rub at the eye. They may be given a course of pain-relieving tablets for five to six days and antibiotic eye drops until re-examination.

The eye is usually more painful than before, but this settles over two to three days.

Rarely, the eye may become very inflamed and reddened. If you are concerned, especially if a severe yellow/green discharge develops or if the eye appears to be persistently very painful, then please give us a call for advice or to arrange a re-check examination.