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In the news: Meta-analysis of Lutein & AMD, Glucose Metabolism & Glaucoma

Role for Lutein in Managing AMD

Researchers from the Dept. of Ophthalmology at one of the largest teaching and research hospitals in Beijing, China conducted a meta-analysis to assess the effectiveness of lutein supplementation in managing age-related macular degeneration (AMD) (1).

Parameters of interest were macular pigment optical density (MPOD) and visual acuity. Heterogeneity of the data was determined and publication bias assessed. Five randomized controlled trials involving 445 participants met the inclusion/exclusion criteria.

Supplemental lutein treatment was associated with highly significant improvement in MPOD, with a mean difference between lutein and placebo groups in the change from baseline of 0.09 (p < 0.00001).
Visual acuity also improved, though less significantly, with a mean difference between groups in the change from baseline of -0.04 (p < 0.05).

The authors conclude that lutein alone is capable of improving MPOD and visual acuity. Though zeaxanthin is also an indispensible component of macular pigment, they point out that lutein is the dominant carotenoid of the two in the diet (provided in ratio of about 5:1 lutein to zeaxanthin). The researchers also note that a lutein dose of 10 mg/day appears to be more efficient as it leads to similar improvements as 20 mg/day.

Glucose Metabolism and Glaucoma Risk

The association between diabetes and glaucoma has been evaluated in many studies. However, few have examined the relationship between metabolic syndrome or glucose metabolism biomarkers and glaucoma, and the results have been conflicting. Two recent studies shed further light on this subject. In the first, a cross-sectional study (2), researchers examined the relationship between diabetes, pre-diabetes, metabolic syndrome, and markers of glucose metabolism with the prevalence of glaucoma in the general US population. They used data from 3,300 participants in the 2005-2008 National Health and Nutrition Examination Survey (NHANES).

A higher prevalence of glaucoma in people with diabetes was seen, even after controlling for multiple potential confounders. Those with diabetes had just over twice the risk of having glaucoma.

Pre-diabetes and metabolic syndrome were not consistently associated with the prevalence of glaucoma. However, markers of glucose metabolism showed significant non-linear associations with glaucoma, including a J-shaped association for fasting glucose, and hockey-stick shaped associations for fasting insulin, HbA1c and HOMA-IR (a measure of insulin resistance). These non-linear relationships suggest that once glucose metabolism markers reach a threshold, the risk for glaucoma increases.

The authors recommend regular eye exams for patients with diabetes, as well as those with elevated levels of glucose metabolism parameters, to monitor for the onset or progression of glaucoma.

In the second study (3), researchers conducted a systematic review and meta-analysis of 47 studies involving more than 2.9 million people from 16 countries to examine the association between diabetes and blood glucose levels with glaucoma, intraocular pressure (IOP), and ocular hypertension.

They found that diabetes, longer duration of having the disease, and elevated blood glucose levels significantly raised the risk for glaucoma. Diabetes and fasting blood glucose levels were associated with slightly higher IOP.

References

1. Wang X, et al. Role of lutein supplementation in the management of age-related macular degeneration: Meta-Analysis of randomized controlled trials. Ophthalmic Res; 52:198-205, 2014.
2. Di Zhao, et al. Diabetes, glucose metabolism, and glaucoma: The 2005–2008 National Health and Nutrition Examination Survey. PLOS ONE; 9:1-7, 2014.
3. Zhao D, et al. Diabetes, fasting glucose and the risk of glaucoma: a meta-analysis. Ophthalmol; Oct 2, 2014 [Epub ahead of print].