Stopping nearsightedness and more.

Stopping nearsightedness and more.

Stopping nearsightedness and more.

Health and medicine explained.
Feb. 27 2007 12:44 PM

Your Health This Week

Stopping nearsightedness in kids and more.

This week, Dr. Sydney Spiesel discusses a way to stop the progression of nearsightedness in kids, a better method of hormone replacement therapy for women after menopause, and new developments in the search for a cause for autism. His column will start appearing a couple of times a month.

Stopping the march of myopia

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Condition: Nearsightedness, or myopia, is the most common eye problem. In the United States and Europe, about 25 percent of the adult population is nearsighted, and in much of Asia the condition is more common still. Significant myopia can have serious medical consequences. It has long been understood that the condition has a strong genetic component: Nearsighted parents are more likely to have nearsighted children. But recent research has shown that other factors contribute. For example, just as our mothers warned us, there is now evidence that doing close-up work, like reading, seems to promote the condition.

How it progresses: The eyeball of a nearsighted person is deeper than the eyeball of a person with normal vision and becomes deeper as nearsightedness progresses. Myopia often begins to develop between the ages of 6 and 8. As children grow, their nearsightedness worsens, continuing to do so long after they have stopped growing taller. Though we know a lot about factors associated with nearsightedness and its progression, we have no good ideas yet about the mechanism. But can we stop it?

New research: A recent study by Wei-Han Chua and colleagues at the Singapore National Eye Center elegantly built on older research and successfully used atropine eye drops to treat myopia in children. Atropine is a longer-lasting version of the pupil-dilating drops your doctor uses when you go for an eye exam. Available by prescription in the United States, the drops are mainly used to treat amblyopia (lazy eye) instead of the older treatment, patching, which children often hate.

Dr. Chua and his co-workers studied the progression of nearsightedness in 400 children between 6 and 12 years of age. Half the children were treated with atropine eye drops, and the other half were treated with placebo eye drops. Both kinds of drops were administered nightly to one eye, so the untreated eye could be compared with the treated one. The children were followed for two years. All used eyeglasses to correct their nearsightedness, and because atropine dilates the pupil, the lenses of the glasses self-darkened in bright light, to avoid discomfort for the children whose pupils were dilated.

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Findings: The effects were extraordinary: After two years, on average, the children's nearsightedness had not progressed in the atropine-treated eyes but had dramatically worsened in the placebo-treated and untreated eyes. Similarly, atropine-treated eyes did not become deeper, while placebo-treated and untreated eyes did. No serious adverse effects were observed in the course of the research.

Conclusion: This is extremely promising. Further work needs to be done to determine the ideal concentration of atropine in the eye drops, to find out how long the treatment needs to last, and if the effects are permanent. Because atropine interferes with close focusing, children will probably need to wear bifocals while they're using the atropine drops. Much more research must be done to help us understand why nearsightedness develops and progresses. But in the meantime, we may have a way to head off this common problem.

Hormone replacement therapy—a safer way

Treatment: Hormone replacement therapy was introduced in 1941, when the FDA approved the use of estrogen for this purpose. Early on, HRT was prescribed with great enthusiasm. It relieved troublesome symptoms associated with menopause, including hot flashes, sleep problems, and, for some women, difficulty in concentration. And HRT (usually estrogen plus a progestin) was shown to improve the bone density of elderly women and decrease their risk for fractures.

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Downside: Time and further research has shown that these gains come at a cost, however: increased risk for cardiovascular problems, stroke, and blood clots in the veins and lungs. Postmenopausal women on HRT also seem to be an increased risk for breast cancer and possibly dementia. This made many women feel they had to choose between improved quality of life and a risk of ill health and early death.

New study: Now research reported in the journal Circulation suggests a way around the blood clotting problem, at least. The researchers studied about 270 women who had developed blood clots in their veins, almost all of them postmenopausal. They were compared with more than 600 women who did not suffer from blood clots but similar in age, smoking status, and age at menopause. Among women in either group who used HRT, the study tracked whether the estrogen medication was taken orally or applied through the skin as a patch or a gel. The nature of the progestin component, if any, was also studied.

Findings: Estrogen HRT increased the risk for blood clots in the veins—but only if it was administered orally. This result is not as surprising as it might seem. A medication that's given orally collects in the blood supply of the intestines and passes through the liver before it is distributed to the rest of the body. This causes changes in the proteins synthesized by the liver, some of which are known to increase the clotting of blood. When the estrogen in HRT is administered through the skin, by contrast, it bypasses the liver. The study also established that some progestins (there are many kinds) increase the risk of blood clotting and that others do not.

Conclusion: If these findings are confirmed, HRT skin patches or gels and careful choice of the progestin component could normalize the risk of blood clots in the veins, and also blood clots that migrate to the lungs, causing pulmonary embolism, and to the brain, causing stroke. Unfortunately, other studies suggest that administering HRT through the skin won't affect the rate of heart disease or risk of breast cancer associated with it. HRT will still be a difficult choice. But this study at least lowers the risk and may well shift the balance for many women.

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The genetics of autism

Search for a cause: It has long been clear that autism is primarily genetic in origin. The disorder is almost certainly the result not of a single abnormal gene, but rather the interaction of several. In the past, a few locations on human chromosomes have been suspected of playing a role for a scattering of patients. Now researchers have identified a genetic location on a specific chromosome that seems to be associated with the expression of autism in many patients.

Newresearch: Described in a paper with 137 authors representing 67 worldwide institutions, this finding is the first result of an audacious project conducted by the Autism Genome Project Consortium. The project started with a set of almost 1,500 families with at least two people who fall on the autism spectrum. Of this group, DNA samples from about 1,200 families could be analyzed for chromosomal similarities.

Findings: This analysis points to a hitherto unsuspected "hot spot" on chromosome 11, which seems to be related to an increased risk for the expression of autism. (The genetic function of the hot-spot location is still unclear.) Besides identifying the chromosome 11 hot spot, the data also tantalizingly hint that flaws in the gene coding for a material called neurexin, which plays a role in the development of certain cell-to-cell transmission sites (synapses), can cause autism in some cases. This trigger for autism is probably quite rare. But it suggests that the disorder is somehow related to abnormalities in the connections between nerve cells that make use of glutamate for information transmission, and defects in those transmissions. How (or even if) these two observations—the hot spot and the neruexin flaws—fit together is as yet unknown.

Conclusion: This study doesn't tell us exactly which gene on chromosome 11 is important, but it does tell us just where to focus our attention. And the neurexin-related discovery hints at the mechanism of what might go wrong in neurodevelopment to lead to autism. These discoveries reinforce the value of collaborative work that puts together information about patients with a relatively rare disorder, from many locales, to create a pool large enough for serious research.