Dr. Grossman’s Blog

Image by Sergio *Savaman* Savarese

Just because you can buy something over the counter doesn’t mean it cannot hurt you.

A review of cases published in the The New England Journal of Medicine shows that “poppers,” legal recreational drugs common in club culture, can cause light sensitivity and vision loss in some individuals.

In an article by HealthDay Reporter, researchers say, “poppers — a catch-all term for alkyl nitrites that are often inhaled by partyers for a brief ‘head rush’ and to increase sexual arousal — may compromise the normal workings of photoreceptor cells found in a key region of the eye’s retina.”  They go on to explain that “nitric oxide is known to affect the metabolism of photoreceptors and can also alter the operation of a key enzyme involved in photoreceptor function.”

Researchers did note that those who stopped taking poppers seemed to recover over a period of several months.  Experts do not yet agree fully on the correlation between the use of this drug and the damage to the eyes; some believe evidence is simply anecdotal at this stage and that more formal research is necessary.

Source: http://www.medicinenet.com/script/main/art.asp?articlekey=120899

Get further information on drugs that harm the eyes.

The 73-year-old, known only as Ron, had the experimental surgery seven months ago at London’s Moorfields Eye Hospital and is now able to see flashes of light, follow white lines on the road, and sort grey and black socks.

The eye known as the Argus II, which was developed by US company Second Sight, uses a miniature camera mounted on glasses to transmit images to the back of the eye.

An “artificial retina” consisting of an array of electrodes sends messages along the optic nerve to the brain.

So far 18 patients around the world have undergone the surgery as part of trials and Ron, who lost his sight in his forties due to the hereditary eye disorder retinitis pigmentosa, was one of three patients to have the device fitted at the London hospital.

As he starts to get use to the device his life will be transformed even more as he gradually learns how to use the artificial eye.

He said: ‘For 30 years I’ve seen absolutely nothing at all, it’s all been black – but now light is coming through.

‘It gives me grades of bright light to black and anything in between. I can actually sort out white socks, grey socks and black socks.’

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.