Dr. Grossman’s Blog

Homocysteine, an amino acid believed to contribute to heart attack, stroke and dementia, may also play a role in retinal damage and vision loss.  Homocysteine levels rise when folic acid levels drop, a common problem for Americans whose diets are often poor in folate-rich fruits, tomatoes, vegetables and grains.

Dr. Sylvia Smith, cell biologist at Medical College of Georgia (MCG), and Dr. Vadivel Ganapathy, chair of the MCG Department of Biochemistry and Molecular Biology are studying the consequence of slightly elevated homocysteine on the retina under a $1.8 million grant from the National Institutes of Health.  They want to learn the impact of elevated homocysteine levels on the extensive blood vessel and neuronal network of the retina; their preliminary evidence suggests that it isn’t good.

“You don’t have to be a cell biologist to see that there is a problem in this retina. It’s terribly disrupted,” Dr. Smith says, looking at images of a fragmented 10-layer retina exposed to high levels of homocysteine.  A healthy retina is “beautifully” organized, horizontally and vertically, she says.

Folate and vitamin B12 convert homocysteine to methionine, an amino acid essential to protein synthesis.  Dr. Ganapathy notes that people need only about 1 microgram per day of vitamin B12, which comes from microorganisms common in animals’ gastrointestinal tract. Strict vegetarians are typically the only Americans who have problems with B12 deficiency, he says. People need about 400 micrograms of folate daily. Pregnant women as well as those trying to become pregnant need at least double that.

Researchers are studying a mouse model with a slightly elevated homocysteine level that simulates a low-folate diet in humans; a version of the mouse that also has diabetes, which goes along with cardiovascular disease and retinopathy; and a second model of the rare genetic defect that results in extraordinarily high homocysteine levels.  These mice will be put on diets that elevate and lower folate levels, so that resultant homocysteine levels and the impact on the retina can be studied.

Researchers hypothesize that sustained elevation will compromise retinal function and degrade the once well-stratified tissue; in pilot studies, the researchers have shown that diabetes exacerbates this problem.

SOURCE:  Medical College of Georgia, “Impact of elevated homocysteine levels on vision under study,” Oct. 15, 2007.

A new study has found that common vision problems known as refractive errors (nearsightedness, farsightedness, and astigmatism) affect half the adult U.S population.

The study authors, led by Susan Vitale of the U.S. National Eye Institute, analyzed data collected by the U.S. Centers for Disease Control and Prevention’s ongoing National Health and Nutrition Examination Survey. In this study an autorefractor was used to obtain refractive error data on a nationally representative sample of 12,010 adults in the U.S. population between 1999 and 2004.

Of the participants (all aged 20 or older), researchers found:

• 3.6% had hyperopia (farsightedness),
• 33.1% had myopia (nearsightedness), and
• 36.1% had astigmatism (an irregular corneal curve)

Other findings:

A study conducted in North India found that people with low levels of antioxidants had higher levels of cataracts.

Several recent studies have shown antioxidants are important in fighting macular degeneration. We are now learning how important these same antioxidants may be for preventing cataracts as well.

How can you boost your antioxidant levels? Eat more fruits and vegetables, especially those high in yellow, orange and dark green pigments.

In this new study 1,112 participants aged 50 or older were interviewed for risk factors (tobacco, alcohol, biomass fuel use, sunlight exposure and socioeconomic status) and underwent lens photography and blood sampling to measure antioxidant levels.

Researchers found significant inverse associations between cataracts and the antioxidants vitamin C, zeaxanthin, lutein, lycopene, alpha- and beta-carotene and beta-cryptoxanthin; people with lower levels of these antioxidants had higher rates of cataracts.

Read more about antioxidants

Learn more about cataracts

Learn more about food sources for nutrients crucial for good eye health

Read more research on antioxidants and their importance for vision

SOURCE: Dherani M, Murthy GV, Gupta SK, et al. Blood levels of vitamin C, carotenoids and retinol are inversely associated with cataract in a North Indian population. Invest Ophthalmol Vis Sci 2008;49(8):3328-35.

NATIONAL EYE INSTITUTE (NEI) SURVEY: Most Americans do not know the risks and warning signs of diseases that could cause blindness without timely detection and treatment, according to recent findings of the Survey of Public Knowledge, Attitudes, and Practices Related to Eye Health and Disease, sponsored by the National Eye Institute and the Lions Clubs International Foundation.

More than 3,000 adults were selected randomly to participate in a national telephone survey conducted between October 2005 and January 2006. Seventy-one percent of respondents reported that a loss of their eyesight would rate as a 10 on a scale of 1 to 10 (meaning that it would have the greatest impact on their day-to-day life); however, only eight percent knew that there are no early warning signs of glaucoma.

Fifty-one percent were aware that people with diabetes are at increased risk of developing eye disease, but only 11 percent knew that there are usually no early warning signs of diabetes-associated eye disease. Only 16 percent had ever heard the term “low vision.” Hispanic respondents reported the lowest access to eye health information and knew the least about eye health; they were also the least likely to have their eyes examined among all racial/ethnic groups in the survey.

NEI plans to use the survey results to raise public awareness of eye disease and the importance of early detection and treatment; it will also expand its educational outreach to Hispanics and increase its efforts to educate healthcare providers on how to communicate with patients about preserving and protecting their vision.