What is the most common metabolic cause of cataracts in dogs?

What is the most common metabolic cause of cataracts in dogs?

• A. Glaucoma
• B. Age-related degeneration
• C. Diabetes mellitus
• D. Uveitis

Answer: (C)

The main concept is that metabolic changes from diabetes mellitus drive cataract formation in dogs. In the diabetic lens, excess glucose enters the lens and is converted by aldose reductase into sorbitol. Because the lens has limited sorbitol dehydrogenase, sorbitol accumulates, creating an osmotic gradient that pulls water into the lens fibers. This osmotic swelling disrupts the orderly arrangement of lens proteins and fibers, leading to cloudiness or opacity. Prolonged hyperglycemia also promotes nonenzymatic glycation of crystallin proteins, which can contribute to opacification, but the osmotic mechanism is the dominant pathway in diabetic cataracts. Other conditions like glaucoma or uveitis can accompany cataracts or cause them secondarily, but they are not the metabolic driver. Therefore, diabetes mellitus is the most common metabolic cause of cataracts in dogs. Clinically, this type of cataract can progress quickly after diabetes starts, and management centers on tight glycemic control to slow progression and, if feasible, surgical removal to restore vision.

The main concept is that metabolic changes from diabetes mellitus drive cataract formation in dogs. In the diabetic lens, excess glucose enters the lens and is converted by aldose reductase into sorbitol. Because the lens has limited sorbitol dehydrogenase, sorbitol accumulates, creating an osmotic gradient that pulls water into the lens fibers. This osmotic swelling disrupts the orderly arrangement of lens proteins and fibers, leading to cloudiness or opacity. Prolonged hyperglycemia also promotes nonenzymatic glycation of crystallin proteins, which can contribute to opacification, but the osmotic mechanism is the dominant pathway in diabetic cataracts. Other conditions like glaucoma or uveitis can accompany cataracts or cause them secondarily, but they are not the metabolic driver. Therefore, diabetes mellitus is the most common metabolic cause of cataracts in dogs. Clinically, this type of cataract can progress quickly after diabetes starts, and management centers on tight glycemic control to slow progression and, if feasible, surgical removal to restore vision.