Macular Degeneration Linked to Infection

[Ms. Kathy]

[glow=red,2,300]Macular Degeneration Linked to Infection[/glow]

No Proof, but Pneumonia Bug a Likely Suspect

By Daniel DeNoon
WebMD Medical News Reviewed By Brunilda Nazario, MD
on Thursday, April 22, 2004


April 24, 2003 -- Age-related macular degeneration may be linked to a pneumonia bug. If so, early antibiotic treatment might prevent some cases of this leading cause of blindness.


There's a lot of suspicion that long-lasting infections may cause many cases of heart disease. The same process could be behind macular degeneration, note Murat V. Kalayoglu, MD, PhD, of the Massachusetts Eye and Ear Infirmary, and colleagues.


If you're rounding up the usual suspects for long-lasting infection, you have to knock on the door of chlamydia bugs. These wily bacteria act like parasites. They can't reproduce outside host cells. And once they infect a person, they like to stick around. There are many types of chlamydia. The most notorious is Chlamydia trachomatis, the bug that causes the sexually transmitted disease known as chlamydia. But its cousin, Chlamydia pneumoniae, is the prime suspect. It's already been linked to heart disease.


Kalayoglu's team looked for evidence of several kinds of chlamydia and E. coli infections in 25 consecutive patients diagnosed with macular degeneration at the VA hospital in Palo Alto, Calif. The researchers also looked for the bugs in 18 patients who didn't have macular degeneration.


Sure enough, tracks of the pneumonia bug -- but not the STD or E. coli bugs -- were found in more patients with macular degeneration than in those without the eye disease.


"These data indicate that C. pneumoniae infection may be associated with age-related macular degeneration," Kalayoglu and colleagues conclude. Their study appears in the April issue of the Archives of Ophthalmology.


A third of Americans over age 75 suffer macular degeneration, a breakdown of the cells lining the center of the retina. Even when macular degeneration does not cause blindness, it can make it impossible to read or drive a car.



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SOURCE: Archives of Ophthalmology, April 2003.

[Ms. Kathy]

Smoking ups risk of age-related eye disorder

May 30, 2005 — NEW YORK (Reuters Health) - Older adults who smoke are twice as likely to suffer from a degenerative eye disorder that is the leading cause of blindness in the elderly as their non-smoking peers, according to findings from the largest study to look at this association in a British population.

Smoking is known to be a risk factor for the disorder called age related macular degeneration (AMD), lead author Dr. Jennifer R. Evans and colleagues, from the London School of Hygiene and Tropical Medicine, note. However, the strength of the association among adults 75 years of age and older in the UK was unclear.

To investigate, they analyzed data from 516 AMD patients and 4364 healthy controls drawn from 49 general practices across Britain.


Current smoking status raised the risk of AMD more than 2-fold compared with non-smoking, they report in the May issue of the British Journal of Ophthalmology. Virtually no excess risk was seen in ex-smokers, especially those who had stopped more than 20 years previously.

Based on these findings, the authors estimate that 28,000 cases of AMD among older adults in the UK may be attributable to smoking.

"An increased risk of AMD, which is the most commonly occurring cause of blindness in the UK, is yet another reason for people to stop smoking and governments to develop public health campaigns against this hazard," the researchers emphasize.

SOURCE: British Journal of Ophthalmology May 2005.

Article source: abcnews.go.com/Health/wireStory?id=803446

[Ms. Kathy]

Scientists Link a Bacterium to Age-Related Blindness
www.nytimes.com/2005/11/15/health/15eye.html?pagewanted=print
By NICHOLAS BAKALAR
A bacterium linked to heart disease may also be a factor in age-related macular degeneration, the leading cause of blindness in people over 55 in the United States.

A new study has found the organism, Chlamydia pneumoniae, in the eye tissue of 6 of 9 patients with macular degeneration, but in none of 22 who did not have the disorder.

The paper, based on work carried out at the Massachusetts Eye and Ear Infirmary in Boston, was published in the November issue of Graefe's Archive for Clinical and Experimental Ophthalmology.

Most vision loss in age-related macular degeneration is caused by the growth of abnormal blood vessels under the retina, a form called neovascular. With it, the vessels bleed, and scar tissue is formed, blocking vision.

One phase in the growth of these blood vessels is the production of vascular endothelial growth factor, the body's response to injury and inflammation.

In this study, researchers using human eye tissue demonstrated that C. pneumoniae may, at least in some cases, be the reason for the inflammation.

While recent studies have shown that drug therapy for the vascular endothelial growth factor can be effective, the underlying cause of age-related macular degeneration is poorly understood.

Dr. Joan W. Miller, the senior author on the paper and chairwoman of the department of ophthalmology at Harvard, remains cautious.

"There is growing evidence that chronic inflammation plays a role in the development of macular degeneration," Dr. Miller said, "and our findings suggest that chlamydia may cause some of this inflammation."

But, she warned, "Our data is very preliminary, and really just supports a link between chlamydia and macular degeneration."

C. pneumoniae is ubiquitous, and almost everyone is infected with it at one time or another. Usually, it causes respiratory illnesses of various kinds and severity. It has also been implicated in coronary artery disease, heart attack and cerebrovascular disease.

Many of the risk factors for cardiovascular disease are risk factors for macular degeneration as well, a fact that led the researchers to wonder whether chlamydia might also be involved in macular degeneration.

Dr. Murat V. Kalayoglu, a research fellow at Harvard who directed the study, pointed out that C. pneumoniae is not the same as chlamydia trachomatis, which causes a sexually transmitted disease, but each form causes a low-grade infection that often has no symptoms.

The authors say their findings do not rule out the "innocent bystander" hypothesis - that C. pneumoniae arrives in tissue after the inflammation has begun, and that it is not the cause.

In addition, because C. pneumoniae was not detected in all of the tissue samples, it is clear that its presence alone is not enough to cause the disease. But the scientists point out that the presence of the pathogen at the site of the disease may accelerate the progression of the disorder in some people.

Detecting C. pneumoniae in eye tissue is not easy. It depends on extracting and then amplifying the DNA of the organism from the tissue, a complex process that is not always reliable, especially when working with preserved tissue samples.

The authors point out that the samples they used had been preserved for several years, and that no tests for chlamydia infection had been performed on the patients at the time of surgery to remove the tissue.

Antibiotic treatment for age-related macular degeneration is still a long way off, Dr. Miller said.

"We would not suggest at this point that treatment for chlamydia be undertaken in patients with macular degeneration," she said.

There are, she added, too many unanswered questions.

"Who do you treat?" Dr. Miller asked. "At what point in the disease process would you begin treatment? For how long would it continue? We need more studies before we are close to answering these questions."

But she added that she was hopeful based on recent clinical trials showing that some patients improved after being treated with drugs directed at the vascular endothelial growth factor.