Type 2 diabetes linked to cortical, posterior subcapsular cataract
MedWire News: Prevention and improved control of diabetes may reduce the burden of cortical and posterior subcapsular cataract, suggest study findings showing these subtypes are associated with diabetes mellitus and glucose levels.
The findings are important as they quantify the association between diabetes and different subtypes of lens opacities, and explain why some patients have a better response to cataract surgery than others.
Using the Lens Opacities Classification System II, Eydis Olafsdottir (University of Iceland, Reykjavik) and colleagues graded lens opacities in 275 patients with Type 2 diabetes mellitus and 256 healthy controls. Patients were aged on average 69 years and had a mean diabetes duration of 9 years.
In addition, the team collected anthropometric and blood chemistry data for all individuals at the time of the eye examination. Yearly updated information on glucose control, blood pressure, and body mass index was available for diabetic patients through medical records.
Among the diabetic patients, 38% were managed with diet alone while 36% took one or more oral hypoglycemic agents and 26% received insulin with or without hypoglycemic agents.
Male patients with Type 2 diabetes had a significantly higher prevalence of cortical lens cataract compared with male patients with no diabetes (64.7 vs 44.9%), while female diabetic patients showed a significantly higher incidence of posterior subcapsular cataract than female controls (51.2 vs 36.7%).
No significant difference was found between the diabetes and the control group regarding nuclear lens opacity.
Regression analysis revealed that all types of cataract were strongly associated with age. The team also found significant associations between cortical lens opacity and a diagnosis of diabetes, posterior subcapsular lens opacity and HbA1c, and between nuclear lens opacity and female gender and higher heart rate.
When the researchers restricted this analysis to patients with Type 2 diabetes, they found that the association with age was present for all cataract types. Furthermore, initial associations with subcapsular cataract and nuclear cataract remained significant.
"The strong and consistent association with a higher heart rate both among the whole study population and among the diabetic group is, to our knowledge, a new finding," comment Olafsdottir et al.
Writing in the journal Acta Ophthalmologica, the researchers conclude: "Whether prevention and improved control of diabetes would reduce the burden of cataract remains to be demonstrated.
"Future studies on the pathogenesis and epidemiology of cataracts must distinguish between the three types of lens opacities, as they clearly show different patterns."
By Ingrid Grasmo