Diabetes mellitus can affect lens clarity as well as the refractive index and accommodative amplitude of the lens. As the blood glucose level increases, so does the glucose content in the aqueous humor (See Chapter 3 in this volume for a discussion of glucose-induced lens changes). Acute myopic shifts may indicate undiagnosed or poorly controlled diabetes mellitus. Patients with type 1 diabetes mellitus have a decreased amplitude of accommodation compared with age-matched controls, and presbyopia may present at a younger age in these patients.
Cataract is a common cause of visual impairment in patients with diabetes mellitus. Acute diabetic cataract, or “snowflake” cataract, refers to bilateral, widespread subcapsular lens changes of abrupt onset and typically occurs in young individuals with uncontrolled diabetes mellitus (Fig 5-19). Multiple gray-white subcapsular opacities that have a snowflake appearance are seen initially in the superficial anterior and posterior lens cortex. Vacuoles and clefts form in the underlying cortex. Intumescence and maturity of the cortical cataract follow shortly thereafter. Although acute diabetic cataracts are encountered in clinical practice only in rare cases today, rapidly maturing bilateral cortical cataracts in a child or young adult may indicate the presence of diabetes mellitus.
Patients with diabetes mellitus develop age-related lens changes that are indistinguishable from nondiabetic age-related cataracts, except that these lens changes tend to occur at a younger age than in those without the disease. The increased risk or earlier onset of age-related cataracts in diabetic patients may be a result of the accumulation of sorbitol within the lens and accompanying changes in hydration, increased nonenzymatic glycosylation of lens proteins, or greater oxidative stress from alterations in lens metabolism. These stressors may promote an increase in nuclear sclerotic cataract, cortical cataract, and PSC formation.
Figure 5-19 Diabetic cataract, or “snowflake” cataract, consists of gray-white subcapsular opacities.
(Courtesy of Karla J. Johns, MD.)
Cataract is the leading cause of visual impairment among children and adolescents with diabetes mellitus and may be the first sign of the disorder or may appear within 6 months of diagnosis. In various studies, the incidence of cataract among pediatric patients with diabetes was between 0.7% and 3.4% of those studied. In a study of 370 pediatric patients with diabetes mellitus, no patients were diagnosed with diabetic retinopathy, but 12 patients had cataract, and 5 of those required surgery. There is no consensus guideline for screening pediatric patients with diabetes for cataract, but some study authors have recommended an eye examination when diabetes is diagnosed and annually thereafter.
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Klein BE, Klein R, Wang Q, Moss SE. Older-onset diabetes and lens opacities. The Beaver Dam Eye Study. Ophthalmic Epidemiol. 1995;2(1):49–55.
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Šimunović M, Paradžik M, Škrabić R, Unić I, Bućan K, Škrabić V. Cataract as early ocular complication in children and adolescents with type 1 diabetes mellitus. Int J Endocrinol. 2018;2018:6763586.
Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.