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Type 2 diabetes may pose a greater threat to the eyes than type 1 diabetes, a retrospective review suggested.

In over 600 individuals with youth-onset diabetes, every diabetic eye-related complication assessed was more common among those with type 2 diabetes versus those with type 1 diabetes, reported Brian G. Mohney, MD, of the Mayo Clinic in Rochester, Minnesota, and colleagues in .

After having diabetes for 15 years, 30.6% of those with type 1 diabetes developed either form of retinopathy versus 52.7% of those with type 2 diabetes.

Specifically, people with youth-onset type 2 diabetes had an 88% higher risk for any type of diabetic retinopathy -- nonproliferative (NPDR) or greater -- compared with those with type 1 diabetes (95% CI 1.13-3.12, P=0.02).

On top of that, those with type 2 diabetes also had a significantly greater risk for developing other serious ocular complications:

• Proliferative diabetic retinopathy (PDR): HR 2.33 (95% CI 0.99-5.50, P=0.048)
• Diabetic macular edema (DME): HR 1.49 (95% CI 0.46-4.89, P=0.50)
• Visually significant cataract: HR 2.43 (95% CI 0.54-11.07, P=0.24)
• Requiring pars plana vitrectomy within 15 years of diagnosis: HR 4.06 (95% CI 1.34-12.33, P=0.007)

In comparing ages of onset, the youngest ages of diagnosis of NPDR, PDR, and DME were 12.6, 18.4, and 19.9 years, respectively, for those with type 1 diabetes compared with 21.4, 23.5, and 23.8 years, respectively, for those with type 2 diabetes.

"This suggests that the natural history of retinopathy development among youth diagnosed with type 2 diabetes may differ from that in youth diagnosed with type 1 diabetes, where patients with [type 2] may be more susceptible to developing retinopathy than those with [type 1] despite controlling for diabetes disease duration," the researchers explained.

Mohney's group performed a medical record review of people from Olmsted County, Minnesota spanning 50 years. They narrowed the analysis down to 606 patients diagnosed with diabetes prior to the age of 22. During this 50-year review period, the incidence of type 1 diabetes was 26 per 100,000 children per year, and type 2 diabetes occurred in 5 per 100,000 children per year. The average age at diabetes diagnosis was 12.

Interestingly, there was a significantly higher proportion of girls in the type 2 diabetes cohort versus the type 1 diabetes cohort (71.9% vs 46.6%). White children made up 83.3% of the type 1 diabetes cohort, whereas Asian and Black children were more likely to have type 2 diabetes than type 1.

Calling this study a "valuable contribution" in an Jennifer K. Sun, MD, MPH, of Beetham Eye Institute at Joslin Diabetes Center and Harvard Medical School in Boston, said these risk estimates are "crucial in setting appropriate screening guidelines for baseline and follow-up retinal examinations."

She highlighted a few more of the study's findings -- particularly the fact that there was 0% risk of developing vision-threatening disease within 5 years after diagnosis in both diabetes groups and that there was a very low risk for advanced retinopathy before puberty.

"These results emphasize the need to explore potential differences between ocular outcomes in patients with type 1 diabetes vs type 2 diabetes and to elucidate the mechanisms behind any differences that do exist," Sun wrote. She added that while the pathophysiology of diabetic retinopathy in both types of diabetes is fairly similar, there's a large difference when it comes to other underlying clinical factors, such as body mass index, lipid profiles, and presence of hypertension. Because of this, she suggested looking into whether these differing factors contribute to the risk differences for diabetic eye disease.

Sun called for more epidemiologic studies on this topic that include diverse cohorts, as well as frequent screening of these at-risk individuals.

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