This is in order to allow production of normal basement membrane and division of normal epithelium. Often further treatment is necessary, such as a keratotomy, which is superficial cutting or piercing of the cornea. There are two main types used in dogs: multiple punctate keratotomy (MPK) and grid keratotomy (GK). MPK involves making small superficial punctures into the cornea with a needle. GK is more commonly used and involves making parallel and perpendicular scratches in the corneal surface. Usually only topical anesthesia is necessary. By scoring the corneal surface, anchoring points are provided for attachment of new epithelium. Of course, these procedures should only be performed by a veterinarian, particularly one with some experience in this treatment. Complete healing takes about three to four weeks. Keratotomies may lead to corneal sequestration in cats. Other medications have been shown to be useful in topical treatment of refractory ulcers, including glycosaminoglycans such as sodium hyaluronate and chondroitin sulfate, aminocaproic acid, and acetylcysteine. Melting ulcers
Melting ulcers are a type of corneal ulcer involving progressive loss of stroma in a dissolving fashion. This is most commonly seen in Pseudomonas infection, but it can be caused by other types of bacteria or fungi. These infectious agents produce proteases and collagenases which break down the corneal stroma. Complete loss of the stroma can occur within 24 hours. Treatment includes antibiotics and collagenase inhibitors such as acetylcysteine and homologous blood serum. Surgery may be necessary.
As a rough guide, a non-infected ulcer can be expected to heal at approximately 0.6mm/day. Complications
In cases where the ulcer is not healing:

Is there a persistent source of irritation? Foreign body
Self traumatisation
Iatrogenic. Is it infected? Review antibiotic therapy
C+S if not already performed. Immunosuppression? Cushings
Steroid therapy. Compliance? Is what youve prescribed getting onto the eye? None of the above? Abnormal epithelium may have formed, keratectomy may be appropriate.Melting ulcers reflect inappropriate collagenolysis of the corneal stroma, by matrix-metalloproteinases (MMPs). Bacterial pathogens (especially Pseudomonas and β-haemolytic Streptococcus) induce the corneal epithelial cells and resident leucocytes to upregulate pro-inflammatory, and MMP-activating cytokines (IL-1,-6 and -8). These bacteria can also produce their own proteinases. The combination of exogenous, and upregulated endogenous, proteinases leads to a rapid breakdown of collagen, with the characteristic melting appearance. Untreated this can lead to perforation within 12 hours (so act hard and fast!). There are several therapeutic options for inhibiting MMPs:

Autogenous serum – administer topically as often as possible. Keep refrigerated and change every 8 days. EDTA  - 0.05% q1h
Acetylcysteine – 5-10% q1h
Tetracyclines – Doxycycline especially has been shown to have anti-MMP effects
Tetanus antitoxin – can be delivered sub-conjunctivally. Contains macroglobulins with anti-collagenase effects.A combination of the above may be necessary early in the disease course. Effective antibiosis is also paramount, and gentamicin is a good empirical choice (although there are some reports of gentamicin-resistant Pseudomonas species). Obviously, treating an eye this frequently in practice will be difficult, so referral is probably the best option. See also
Corneal abrasion
Keratitis


== References ==