There are three groups of corneal lesions that appear with crystalline corneal opacities. Many of the clinical features are similar in these diseases, although the underlying causes of the opacity differ. These groups include corneal dystrophies, lipid keratopathy, and corneal degeneration.
Corneal Dystrophy is commonly a bilateral condition that is inherited. It is not accompanied by corneal inflammation or systemic disease. Most corneal dystrophies in the dog appear a grey-white or silver, crystalline or metallic opacities in the central or paracentral cornea. The mostly oval or circular lesions are often nearly symmetric in both eyes.
Lipid Keratopathy has been associated with systemic abnormalities, such as hypothyroidism, pancreatitis, diabetes mellitus, spontaneous hyperlipoproteinemia, and postprandial plasma lipid elevations. It can be bilateral or unilateral and can be seen as peripheral or central corneal opacities.
Corneal Degenerations are crystalline corneal opacities secondary to pathologic changes within the cornea. Vascularization is a hallmark of those lesions.
To rule out corneal infiltration from systemic disease in cases that do not appear typical of hereditary dystrophy, serum chemistry panels, levels of cholesterol and triglycerides, glucose levels, as well as evaluation of thyroid and adrenal function are recommended.
Crystalline corneal opacities usually do not cause discomfort. However, in some cases some crystals may brake off and create a corneal ulcer, which is painful and requires treatment with eye medications. Eye medications cannot decrease the amount of lipid crystal. In more severe cases or cases with secondary non-healing ulcerations the lesions can be surgically removed.