What is Inherited Corneal Disease?
The center of the cornea is the part most often affected by corneal dystrophy. These deposits begin to develop when the epithelium has not correctly attached to the descemet membrane. This causes erosions to develop in the cornea which heal very slowly. Deposits of triglycerides and cholesterol begin to fill the erosions. This occurrence is referred to as “lipidosis”. Most cases do not cause pain in the cat, however advanced cases may lead to irritation of the eye and eventual blindness. If bullae (bubble-shaped cavities in the cornea) form, they may be quite painful for the cat. Veterinary attention can provide aid to cats suffering symptoms from inherited corneal disease.
The cornea is the eye's frontmost outer layer. It is clear and dome-like in shape. It is constructed of the stroma, basement membrane, endothelium, descemet membrane, and epithelium. Cats who have inherited defective corneal genes may begin to develop visible deposits in the eye called “corneal dystrophies”. These deposits are often cloudy-white in color, and can vary greatly in shape and size. The condition is rare in cats, but if it is present it will often begin to show while the cat is still young.
Symptoms of Inherited Corneal Disease in Cats
In some cats, corneal dystrophy will begin unilaterally (on one side), affecting one eye first and then spreading to the other. Depending on the part of the eye that is affected, some cases will form bilaterally (in both sides) and show as symmetrical deposits in both eyes. Signs to watch for include:
- Visible white, opaque spots in the eye
- Ulcerations and erosions on the cornea
- Symmetrical deposits in both eyes
- Blindness in advanced cases
- Ocular pain
Causes of Inherited Corneal Disease in Cats
Corneal dystrophy can result from defective genes being passed down from one or both of the cat's parents. It occurs more often in purebred cats than in mixed breeds, indicating that inbreeding may be at fault for the defect. It can exist as a recessive gene in Manx breed cats.
Diagnosis of Inherited Corneal Disease in Cats
If symptoms have begun to show and you are concerned about possible pain in your cat, take it in to your veterinarian for a professional assessment. The vet will perform a complete physical and ophthalmologic examination on the cat. A magnified visual of the affected eye will show an appearance like crushed glass in the deposit areas. Provide your veterinarian with the cat's full medical history so that other possible causes of corneal disease can be ruled out.
To determine the composition of the deposit, a biopsy may be taken, frozen and sent off to a lab for a histopathological examination. This can help to differentiate lipid deposits from other opacities of the cornea. Full blood work should be run including a complete blood count and a biochemical profile to assess the overall health of the cat and monitor its cholesterol and triglyceride levels. High cholesterol can exacerbate the dystrophy. Applying fluorescein stain to the cornea can help identify where the issue is. If a lipid deposit is present near the surface, the stain will not be retained, however if the issues involve the epithelium or endothelium, the stain will stay. Tests for feline leukemia virus and for hypothyroidism should be run, as they also can cause lipid deposits in the cornea.
Treatment of Inherited Corneal Disease in Cats
If the cat is not exhibiting symptoms, treatment may be unnecessary. If pain or impaired vision are present, treatment should be sought. Earlier diagnosis and treatment is more successful as damage may not yet involve the whole cornea.
Often hyperosmotic (a liquid more dense in solute particles than cellular liquid) eye drops will be prescribed to treat irritation from corneal dystrophy. Frequent administration of the medication can improve the health of the cells above the lipid deposits.
Heat is used to shrink the collagen stroma of the cornea and flatten the affected corneal area. This can improve severe nearsightedness in the cat.
This is a corneal transplant surgery in which a circular section of the diseased cornea is removed and replaced by a healthy cornea from a donor. A laser is used to perform this procedure. Veterinary clinics that offer this surgery are rare. It is only used in extreme cases and is a very expensive operation.
In this surgery, corneal deposits are removed and the wound area is left empty. Sometimes grafting from another area is needed for the healing process to take place, depending on the size of the deposit.
Topical Acid Treatment
This procedure may be repeated until the desired result has been reached. The acid will slowly dissolve any lipid deposits present.
Recovery of Inherited Corneal Disease in Cats
If your cat has undergone eye surgery, follow all guidelines given for proper at-home care. The surgical site should be monitored daily to ensure no signs of infection have begun to develop. Surgical intervention can lead to further problems such as bleeding of the eye, ulcerations, uveitis and glaucoma. Lipid deposits may reform in cats who have undergone surgery. Be sure to administer all medications as prescribed.
If your cat is continuing to exhibit signs of pain, or if visible ulcerations are present, multiple follow-up appointments with the veterinarian may be needed. Cats with inherited corneal disease should not be bred, in order to prevent the defect from passing on. The cat's diet should be evaluated, as consuming foods high in fat can make deposit development worse. An appropriate diet to handle corneal dystrophy is low in fat and high in fiber.