Cataracts are one of the common complications of diabetes. Diabetic cataracts can be categorized into two types: true diabetic cataracts and age-related cataracts in diabetic patients.
Etiology
The lens derives its energy primarily from glucose in the aqueous humor. Glucose metabolism in the lens occurs mainly through anaerobic glycolysis. Under the action of hexokinase, glucose is converted into glucose-6-phosphate. When aldose reductase and coenzyme II are involved, glucose is converted into sorbitol. In diabetes, elevated blood glucose levels lead to an increase in glucose within the lens. When the activity of hexokinase becomes saturated, the conversion of glucose into glucose-6-phosphate is inhibited. At this stage, aldose reductase activity becomes activated, promoting the conversion of glucose into sorbitol. Sorbitol cannot pass through the lens capsule and accumulates extensively within the lens. This increases the osmotic pressure within the lens, leading to water absorption, swelling, degeneration of the lens fibers, and the resulting opacities.
Clinical Manifestations
True diabetic cataracts are more commonly observed in adolescents with type 1 diabetes. They typically affect both eyes, progress rapidly, and may quickly result in total opacification of the lens, presenting as mature cataracts. Refractive changes often occur alongside the cataracts. Elevated blood glucose levels lead to a decrease in inorganic salts in the blood, prompting aqueous humor to enter the lens and causing it to become more convex, which results in myopia. Conversely, when blood glucose levels decrease, water is discharged from the lens, causing it to flatten and leading to hyperopia.
Diagnosis
The diagnosis is based on a history of diabetes and the morphological characteristics of the cataracts.
Treatment
In the early stages of diabetic cataracts, effective management of diabetes is essential. Partial resolution of lens opacities and some improvement in vision may occur. When cataracts significantly impair vision and interfere with the patient's daily activities or work, cataract extraction can be performed under controlled blood glucose levels. In the absence of proliferative diabetic retinopathy, posterior chamber intraocular lens implantation may be performed. Postoperative care requires special attention to the prevention of infection and bleeding.