Adults with metabolic syndrome at increased risk for open-angle glaucoma

Ophthalmology. 2011;118(7):1318-1326.

Issue: October 10, 2011

Patients with diabetes mellitus, systemic arterial hypertension, hyperlipidemia and obesity have elevated risks of developing open-angle glaucoma, a large study found.

"Given that approximately one-fifth of the U.S. population has metabolic syndrome and that both metabolic syndrome and OAG increase in prevalence with age, our data suggest that as the U.S. population ages, the disease burden of OAG may increase in the coming years," the study authors said.

The longitudinal cohort study included 2,182,315 adults aged 40 years or older enrolled in a managed care network who visited an eye care provider at least once between 2001 and 2007. Mean patient age was 54.5 years.

The authors performed statistical analysis to determine patients' risk of developing open-angle glaucoma (OAG) in conjunction with individual and combined types of metabolic syndrome. Data were adjusted for social and demographic factors, systemic medical conditions and other ocular diseases, the authors said.

Raw data showed that 1,576,993 subjects had at least one metabolic disease; 55,090 subjects had OAG.

Adjusted data showed that subjects with diabetes alone had a 35% increased risk of developing OAG, and those with hypertension alone had a 17% increased risk. Those with diabetes and hypertension combined had a 48% risk. Those with hyperlipidemia alone had a 5% decreased risk. Obese subjects had a 14% increased risk.

Subjects with diabetes, hyperlipidemia and hypertension combined had a 26% increased risk.

Risk of developing OAG was higher in African Americans, Latinos and Asian Americans than in Caucasians, the authors reported.

The key sentence in this paper is the authors’ admission: “It is certainly possible that individuals with DM are more likely to have an eye examination than the general population and are therefore more likely to receive a diagnosis of OAG.” Previously, we accepted the dictum that diabetes and hypertension were glaucoma risk factors. This came from the ascertainment bias that diabetics (appropriately) get more eye exams than non-diabetics when they are within the health care system, and, from the known fact that diabetics have higher measured IOP than non-diabetics, leading eye doctors to be more likely to call them “glaucoma.” Most population-based studies that use a modern definition of open-angle glaucoma find no association between diabetes and OAG, while those that include “high” IOP in the definition do see an association. We now know that including IOP in OAG definition is a mistake. Large database studies can provide some useful information, but when over-interpreted, as here, they fail to account for the inevitable selection bias in assigning risk factor associations from such data. No one would dispute the importance of eye exams for diabetic persons to prevent their development of blinding retinopathy. But, as seen in the OHTS clinical trial, if anything, diabetes is neutral or even protective for development of OAG. For more detail see: Quigley HA. Can diabetes be good for glaucoma? Why can’t we believe our own eyes (and data)? Arch Ophthalmol. 2009;127:227-229.

– Harry A. Quigley, MD
Director, Glaucoma Center of Excellence, Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore
Disclosure: Dr. Quigley has no relevant financial disclosures.