There are three different ophthalmological conditions that present as opaque areas on the cornea of a dog's eye as a result of lipid or calcium deposits. The three conditions are corneal dystrophy, corneal degeneration and lipid keratopathy. Corneal lipidosis is the collective term for these conditions. While corneal dystrophy is usually an inherited and primary condition, lipid keratopathy is a secondary problem that usually results from underlying health conditions.
Presentation of Lipid Keratopathy
Lipid keratopathy is defined as an ophthalmological condition in which deposits of lipids, or fats, infiltrate the cornea of the eye. The presentation may be unilateral or bilateral, and when both eyes are affected, the opacities are not symmetrical. The lipid deposit has a flecked appearance. As the condition progresses, the affected eye becomes more inflamed, tiny blood vessels may appear on the opaque surfaces and corneal degeneration can subsequently set in.
Since it can often be challenging to differentiate between lipid keratopathy and corneal degeneration, dogs who present with an opacity in one or both eyes should be examined by a board-certified veterinary ophthalmologist. He will be able to conduct specialized ocular tests, including a slitlamp biomicroscopic examination of the eye, to make a definitive diagnosis and pursue the appropriate course of treatment.
The Ocular Effect of Hyperlipidemia
Lipid keratopathy occurs as a result of hyperlipidemia, which is the condition of having a high level of lipids, or fat molecules, in the blood. Cholesterol and triglycerides are the essential lipids in your dog's body. These fats are insoluble. To travel through the bloodstream to your dog's organs and tissues, they require the help of lipoproteins, which are produced by a healthy dog's body. When an insufficient amount of lipoproteins are formed, the cholesterol cannot circulate through the blood as efficiently and it accumulates. The excess lipids form deposits within the blood vessels, as well as on the cornea of the eye. While hyperlidemia is the secondary cause of lipid keratopathy, your veterinarian must evaluate your dog's medical history and perform laboratory screenings to determine the primary cause, that is, the cause of your dog's hyperlipidemia.
The Root of the Problem
Lipid keratopathy and hyperlipidemia most commonly result from an underlying health problem. Some of these conditions include:
- Hypothyroidism, a condition in which a dog has abnormally low levels of thyroid hormones.
- Diabetes mellitus, a condition in which a dog's pancreas fails to produce adequate levels of insulin.
- Cushing's disease, a condition in which a dog has abnormally high levels of cortisone.
- Protein-losing nephropathy, a condition in which the kidneys fail to filter proteins, and the proteins are lost from the body when the dog urinates.
Certain breeds, such as miniature schnauzers, are genetically predisposed to developing hyperlipidemia. Some medications, such as corticosteroids, or a diet that is high in fat can elevate a dog's lipid levels.
Treatment and Prognosis
Treatment for lipid keratopathy must focus on treating the underlying cause. Diabetes, hypothyroidism and Cushing's disease can all be managed with medication and monitoring through periodic laboratory screenings. Feeding a low fat diet may be recommended in an attempt to reduce the lipid levels. In some cases, ophthalmic medications may be prescribed to reduce the eye's inflammation, but there are no medications that will eliminate the lipid deposits. There is a surgical procedure, called a keratectomy, in which the outer layer of the cornea is removed, but this is not curative and the condition usually recurs. Lipid keratopathy is painless and notable vision loss is not a consequence of this condition.