Cataract is considered a major cause of visual impairment in people living with diabetes as the incidence and progression of cataract is elevated. Cataracts are among the earliest complications of diabetes. Remarkably, impaired fasting glucose (IFG), a pre-diabetes condition, has been considered as a risk factor for the development of cortical cataracts 2. While for those with an older onset of diabetes, cataracts are the most common cause of visual impairment3.
Several clinical studies have shown that cataract development occurs more frequently and at an earlier age in those living with diabetes compared to those without. Patients with diabetes are 2–5 times more likely to develop cataracts than their diabetes-free counterparts; this risk may reach 15–25 times in those with diabetes less than 40 years of age. There is a three to fourfold increased prevalence of cataract in people with diabetes under the age of 65, and up to a twofold increase in prevalence in people above 65 1.
Cataracts may develop at an earlier age and may have a higher prevalence rate in patients with diabetes due to hyperglycaemia 4,5 and the compromised blood–aqueous or blood–retina barriers . Breakdown of these barriers may also worsen postoperative inflammation after cataract surgery, and may initiate the progression of Diabetes-related Retinopathy 6. Up to 20 % of cataract surgeries are performed on patients living with diabetes 3 .Per million people with diabetes 440 eyes will require cataract surgery annually 4.
The “Wisconsin Epidemiologic Study of Diabetes-related Retinopathy” investigated the incidence of cataract extraction in people with diabetes. Cataract surgery was 8.3% in patients suffering from type 1 diabetes and 24.9% in those from type 2 diabetes. Predictors of cataract surgery included age, severity of Diabetes-related Retinopathy and proteinuria in people living with type 1 diabetes, whereas age and use of insulin were associated with increased risk in people living with type 2 diabetes 1.
Several studies have compared different types of cataracts in people with diabetes versus people without diabetes.
An uncommon type of lens opacity, referred to as a true diabetic cataract or snowflake cataract, consists of widespread subcapsular lens opacities of abrupt onset and acute progression, typically in young people with challenging diabetes. This is rare and some suggest this may be the initial presentation of diabetes 3.
In a Beaver Dam Eye study 5, the incidence and progression of cortical and posterior subcapsular cataract was associated with diabetes, with longer duration of diabetes associated with an increased frequency of cortical cataract as well as an increased frequency of cataract surgery. In a Blue Mountains Eye Study, posterior subcapsular cataract was shown to be statistically significantly associated with diabetes 1. Additional studies also support a higher percentage of cortical cataracts in people with diabetes 7, 2.
Other risks for diabetes related catraracts include untreated uveitis and prolonged corticosteroid treatment of ocular surface complications or of Diabetes-related Macular Edema (DME) 8.
Incidence rates of cataracts among people with diabetes has been investigated for some countries for example:
- In the UK population of people with diabetes the incidence of cataract is 20.4 per 1000 person-years compared to 10.8 per 1000 person-years for people without diabetes 9
- In the Russian Federation study 30.6% of 7,186 people with diabetes reported the presence of cataracts 10.