Corneal Dystrophy in Dogs

What is corneal dystrophy?

Corneal dystrophy is a condition that causes the corneas to become opaque (cloudy). There are three major categories of corneal dystrophy: epithelial, stromal, and endothelial. Each is named based on the anatomic location of the abnormal tissue and opacity. All corneal dystrophies are primary, inherited conditions, not associated with any other eye disease or systemic (body-wide) medical problem. Corneal dystrophy is very rare in cats.

How do the three types of corneal dystrophies differ from one another?

The three types of corneal dystrophy are named by their anatomic location in the cornea, and consequently the clinical signs of each differ.

Epithelial corneal dystrophy

In this type of corneal dystrophy, opacity (cloudiness) occurs in the superficial layers of the cornea. Epithelial corneal dystrophy has been found in many dog breeds. Many dogs with epithelial corneal dystrophy have no clinical signs other than corneal opacity. However, some dogs may have corneal pain that causes squinting and sensitivity to light. The surface of the eye may develop patches of white or gray; these are opaque lesions, and some of the lesions may lead to erosions in the corneal surface. The erosions lead to eye pain.

Stromal corneal dystrophy

The stroma is the middle layer of the cornea, and stromal corneal dystrophy is associated with the deposit of fat droplets or minerals into this layer of the cornea. Multiple breeds are affected, including the Airedale, cocker spaniel, bearded collie, Cavalier King Charles spaniel, Samoyed, and Weimaraner.

These dogs tend to be young when diagnosed, and most dogs have no associated inflammation or pain. The opacity tends to occur in one of several patterns, most commonly as a gray, white, or silver opacity at or near the center of the cornea. Alternately, the opacity may appear as a ring around the outer border of the cornea, or the entire cornea may become diffusely opaque. Vision may be affected when the opacity is diffuse (spread out).

Endothelial corneal dystrophy

Endothelial corneal dystrophy affects the deepest layer of the cornea. This condition is most common in middle-aged or older Boston terriers, Chihuahuas, and Dachshunds. In the early stages of endothelial dystrophy, there may be no easily observable signs. As it progresses, fluid accumulation (edema) starts at the lateral edge of the cornea and spreads across the rest of the cornea over time. These dogs may develop painful corneal ulcers and may lose their vision with advanced disease.

Is there any treatment for corneal dystrophy?

Advanced epithelial or endothelial corneal dystrophy may result in corneal ulceration that requires treatment. A referral to a veterinary ophthalmologist (eye specialist) may be recommended, especially with repeated or complicated corneal ulceration. Most dogs with corneal dystrophy never experience compromised vision.