A corneal ulcer is the loss of a portion of the epithelium on the cornea. 

An indolent corneal ulcer is the result of a corneal defect.  This is also known as a refractory epithelial erosion.  This defect is found in the superficial portion of the corneal stroma just beneath the epithelium.  The defect does not allow the epithelium to stick to the underlying stroma and, as a result, these ulcers do not heal with simple medical therapy or take an extremely long time to heal. 

Introduction

• To understand a corneal ulcer, it is important to have a basic understanding of the anatomy of the cornea.  The outer most layer of the cornea is a protective barrier called the epithelium.  Beneath this is a layer that makes up the majority of the cornea called the stroma.  It is the highly structured anatomy of this layer that allows the cornea to be clear.  On the inside of this layer is an elastic-like membrane called Descemet’s membrane.  Internal to this there is only a one cell thick layer called the endothelium. 
• A corneal ulcer is the loss of a portion of the epithelium.  In a simple corneal ulcer, the remaining epithelium will slide over the ulcerated area and heal the ulcer in a few days.  There are several situations in which this does not occur and one of these is the indolent corneal ulcer.

What is an Indolent Corneal Ulcer?

• An indolent corneal ulcer is the result of a corneal defect.  This is also known as a refractory epithelial erosion.  This defect is found in the superficial portion of the corneal stroma just beneath the epithelium.  The defect does not allow the epithelium to stick to the underlying stroma and, as a result, these ulcers do not heal with simple medical therapy or take an extremely long time to heal.  These ulcers will sometimes cause blood vessels to grow into the cornea resulting in scarring when they take too long to heal.  Indolent corneal ulcers are also called persistent corneal ulcers, refractory corneal ulcers, or boxer ulcers, due to the frequency that the problem is seen in this breed.

What is a Typical Scenario?

• Indolent corneal ulcers are seen in middle-age to older dogs.  Ulcers that look like indolent corneal ulcers in young dogs are often due to chronic ongoing irritants such as abnormal eyelash hairs or foreign bodies.  The disorder is seen frequently in Boxers and Golden Retrievers however, any breed can be affected.  Unlike other types of corneal ulcers, no trauma is required to create indolent corneal ulcers.  Usually these dogs have been treated with standard medical therapy without resolving the problem, or the ulcer continually gets better and worse.

What is the Treatment?

• Indolent corneal ulcers are the result of a defect in the superficial layer of the corneal stroma, so treatment is aimed at this defect.  All the loose epithelium on the cornea is removed.  In most cases, after this is performed, a procedure called a grid keratotomy is performed.  In this procedure, a needle is used to make small hatch marks into the ulcerated area of the cornea to get through the defect.  This will sometimes be performed with topical anesthesia alone, but may be recommended under general anesthesia.  In more difficult cases, the superficial layer of the cornea may need to be removed under general anesthesia.  After the procedure a contact lens or a dissolving contact lens called a collagen shield may be placed.  Medical therapy after these procedures is similar to a simple corneal ulcer, consisting of a topical antibiotic drop and often a drop to dilate the pupil.  These procedures will usually heal this type of ulcer in 2-3 weeks. 

What Can I Expect Long-Term?

• Early recognition of this disorder is important as the longer the ulcer remains, the more likely blood vessel growth into the cornea is.  If there is significant vessel growth into the cornea, this will decrease over time.  There are also medications that can be used to try to make the vessels resolve more quickly once the ulcer is completely healed.  It is important to understand that because this is a defect in the cornea, the opposite eye will often times become affected.  You should be vigilant to watch for signs in the other eye and bring the dog in right away if you notice anything.