From the Journals

Smoking, hypoglycemia, kidney function tied to vision loss in type 2 diabetes



Several risk factors, including smoking, a previous severe hypoglycemic event, and poorly functioning kidneys, can lead to vision loss in patients with type 2 diabetes, according to new findings published in the Journal of Diabetes and its Complications.

“Smoking cessation strategies and optimal cardiometabolic risk factor management, including blood glucose lowering regimens that minimize hypoglycemia, appear important in preventing the loss of vision associated with type 2 diabetes,” wrote Jocelyn J. Drinkwater of the University of Western Australia, Perth, and coauthors, noting that all three noted risk factors were “potentially modifiable.”

To investigate the impact of type 2 diabetes and associated risk factors on vision, the researchers recruited 1,732 participants for the Fremantle Diabetes Study Phase II, of whom 1,551 patients had type 2 diabetes and underwent face-to-face and visual acuity assessments at baseline and at 2 and 4 years. Visual acuity was measured via the Bailey Lovie chart at a distance of 3 m in a well-lit room. Normal or near-normal vision was classified as a visual acuity of equal to or less than 6/19; visual impairment, a visual acuity of greater than 6/19 and equal to or less than 6/48; and blindness, a visual acuity of greater than 6/48. A change in vision was classified as a difference in visual acuity of more than 10 letters from baseline measurement.

Of the initial 1,551 participants, 31 were excluded because of missing baseline data for visual acuity. The remaining group comprised 52.2% men, the mean age was 65.6 years, and the median diabetes duration was 8.5 years (interquartile range, 2.9-15.8). At baseline, the prevalence of visual impairment was 1.8% (28 patients), and prevalence of blindness was 0.7% (11 patients), so those 39 patients were also excluded from further analysis.

After 4 years, 599 patients (39%) were excluded because of attrition or missing data; among them, 138 (23%) died before the follow-up.

The remaining 882 participants (58%) had their visual acuity measured. Among these patients, 62.2% were men, with a mean age of 65.1 years and an initial median diabetes duration of 7 years (IQR, 2.0-15.0). Their cumulative incidence of visual impairment was 0.9% (eight patients), and no patients with normal or near-normal vision had developed blindness. Cumulative incidence of vision loss was 2.9% (26), and 1.9% (17) had improved visual acuity.

After multivariable logistic regression to determine predictors for vision loss, the researchers found that participants who smoked at baseline were more than three times more likely to lose their vision (odds ratio, 3.17; 95% confidence interval, 1.15-8.76; P = .026). Although smoking was noted as a “well-recognized risk factor for ocular disease,” the authors added that ex-smokers did not have significantly higher odds of vision loss, compared with nonsmokers, suggesting that the “ocular damage caused by smoking may not be permanent.”

Participants who had suffered a severe hypoglycemic event before the study were five times more likely to lose their vision (OR, 5.59; 95% CI, 1.32-23.61; P = .019). The authors emphasized that severe hypoglycemia can worsen existing ischemic tissue damage or contribute to a long duration of poorly controlled diabetes, each of which could “increase the risk of ocular complications leading to impaired vision.”

The final notable risk factor was compromised kidney function, which is identified as a urinary albumin-creatinine ratio (uACR). The authors noted that the uACR has been associated with other ocular pathologies, such as retinopathy and macular edema, and that uACR may be a “surrogate marker of a variety of ocular diseases with shared risk factors, such as poor metabolic control, which have implications for vision.”

In regard to the possible limitations of the study, they authors noted that they had not used the “gold standard” Early Treatment Diabetic Retinopathy Study chart to assess visual acuity. In addition, although they had details on retinopathy, cataracts, and glaucoma status, they did not also consider less common ophthalmic conditions. Finally, as a survivor cohort, they acknowledged that they may have “underestimated the cumulative incidence” of vision issues in the participants.

The study was supported by the National Health and Medical Research Council of Australia. The authors reported no conflicts of interest.

SOURCE: Drinkwater JJ et al. J Diabetes Complications. 2020 Feb 20. doi: 10.1016/j.jdiacomp.2020.107560.

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