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A Harvard Medical School doctor answers a common eyesight question

Q: Recently, I started to notice tiny threadlike shapes in my field of vision. My doctor says they are "floaters." Should I be concerned?

A: "Floaters" is a catchall term for what look like dots, threads, or cobwebs drifting across your line of vision.

If you have a hacking cough and breathlessness, don't chalk it up to aging.

Maybe you never smoked, or you stopped decades ago. But you may still be at risk for chronic obstructive pulmonary disease (COPD). That's the umbrella term for a number of lung diseases that sometimes lead to disability and even death. "While about 80% of COPD cases are related to having smoked, 20% are not," says Dr. Bartolome Celli, a pulmonologist with Harvard-affiliated Brigham and Women's Hospital.

Diseases and symptoms

COPD includes emphysema, chronic bronchitis, severe asthma, or a combination of these conditions. They cause inflammation, destruction, or abnormal repair of airways and lung tissue, which reduces airflow and ultimately makes it harder to take in enough oxygen to supply the body.

A rapid heartbeat can be frightening, but this often-fleeting problem is usually harmless.

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If you're exercising or feeling very nervous, you expect your heart to beat faster than normal. But what if your heart sometimes starts racing out of the blue, for no apparent reason? You might have supraventricular tachycardia, or SVT. SVT is an umbrella term that covers several different types of rapid heart rhythms, all of which are caused by an electrical glitch in the upper part of the heart.

The most common SVTs are atrial fibrillation � a rapid, chaotic rhythm that increases the chance of having a stroke—and atrial flutter, a fast but usually regular heartbeat. But when cardiologists talk about SVT, they're usually referring to three different, less-common conditions (see "What is supraventricular tachycardia?").

Ask the doctor

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Q. Several years ago you wrote about a new technology called CRISPR that might make it possible to cure some incurable diseases. I keep hearing about this in the news. Is it any closer to reality?

A. Yes, there has been progress. What does CRISPR stand for? You don't want to know. What does it do? You do want to know, because it's pretty amazing. A colleague here at Harvard Medical School, Dr. George Church, says CRISPR enables a scientist to "edit any piece of any DNA a thousand times more easily and precisely than before, which is game-changing for gene therapies." Why would doctors and scientists want to "edit" DNA? Because disease is caused by genes that are not built properly or are not turned on and off properly. Both problems, theoretically, can be corrected by precisely editing the DNA that makes up those genes.

Most people who are suffer from fecal incontinence do so in silence. As a result, the number of people with the condition � which results in the involuntary release of gas or stool � isn't known. But the scant evidence at hand indicates that it usually begins during one's 40s or 50s.

You don't have to live with incontinence � there are treatment options, which include dietary changes and bowel training regimens, and surgery for some people.

This common type of arthritis can show up suddenly and cause debilitating pain.

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The great artists Ludwig van Beethoven, Luciano Pavarotti, and Leonardo da Vinci had more than extraordinary talent in common; they were also sufferers of a type of inflammatory arthritis called gout. You may be at risk of joining their ranks if you have any potential triggers for the condition. "Most people are surprised by their initial gout diagnosis, unless they have a strong family history," says Dr. Mark Fisher, a rheumatologist at Harvard-affiliated Massachusetts General Hospital.

About gout

Gout is mostly a man's condition, although women can experience it, too. It's caused by a buildup of uric acid � a waste product from the breakdown of natural chemicals called purines (an essential part of DNA).

Because medications cannot effectively treat aortic stenosis, a stiff, narrowed aortic valve needs to be replaced.

Your aortic valve is the gateway between your heart and body. With every heartbeat, it opens to allow blood to flow to your body, then snaps shut to keep blood from moving back into the heart.

As people age, calcium deposits may collect on the hard-working aortic valve, causing it to stiffen and narrow. Known as aortic stenosis, this condition also can result from a genetic abnormality (see "What is a bicuspid aortic valve?"). But most cases are in older people, often � but not always � those with high blood pressure, high cholesterol, and other risk factors linked to heart disease. In the United States, about three to four of every 100 people ages 75 and older have severe aortic stenosis.

On call

Q. I have had a dandruff problem for years. I have tried selenium and zinc shampoos, as well as ketoconazole shampoo. Nothing has worked. Are there other options?

A. Dandruff, which is a chronic skin condition known as seborrheic dermatitis of the scalp, can range from a minor irritant to a severe rash of the entire scalp.

Don't be surprised if your doctor doesn't rush you into treatment.

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Urinary tract infections (UTIs) can be tricky in older age. They're not always as easy to spot or treat as in youth. And the decades-long approach to treatment is changing. "We've been hasty in using antibiotics, and we're learning there are significant consequences that can range from side effects of medication to infections with antibiotic-resistant bacteria," says Dr. Helen Chen, a geriatrician at Harvard-affiliated Hebrew Rehabilitation Center.

About UTIs

UTIs can occur anywhere in the urinary tract. The most common places are the bladder (where urine is stored) and the urethra (the tube through which you urinate). Less common, but more serious, is infection of the kidneys, which filter waste and extra water from the blood and make urine. Infections may be triggered by sexual activity, catheters, kidney stones, decreased estrogen in the lining of the vagina, or urine that's pooled in the bladder.