First, a bit of biology ... The lens in the front of your eye focuses light on the retina in the back of your eye. The lens is like the one in a camera, and the retina is like film. The space between the lens and retina is filled with the vitreous, a clear gel that helps to maintain the shape of the eye.

Riding a bike gives you a substantial workout. I enjoy riding bike trails because I get to enjoy nature while getting low-impact exercise. I gave up riding on streets because there are too many dangers posed by cars and trucks. If you don’t want to ride outdoors, you can pedal a stationary bike indoors.

TIA stands for “transient ischemic attack.” A TIA is an interruption in the flow of blood to a part of your brain. Its symptoms are the same as for a stroke. A TIA lasts anywhere from minutes to many hours. It goes away and leaves no apparent permanent effects.

Doctors say you have high blood pressure if you have a reading of 140/90 or higher. A blood pressure reading of 120/80 or lower is considered normal. Prehypertension is blood pressure between 120 and 139 for the top number, or between 80 and 89 for the bottom number.

The techniques I will mention here should not substitute for seeing a doctor about a medical problem. Relaxation techniques are generally considered safe for healthy people, but you should tell all your health-care providers about relaxation methods you are considering.

The outer layer of the tear film, which is produced by small glands on the edge of your eyelids, contains fatty oils. These smooth the tear surface and slow evaporation of the middle watery layer. If your oil glands don’t produce enough oil, the watery layer evaporates too quickly, causing dry eyes.

Lyme disease can cause fever, headaches, fatigue, joint pain, sore muscles, stiff neck and a skin rash that usually begins where the tick dug in. The rash may start out as a small red spot that can get bigger. A ring within the spot can fade and create a “bull’s eye.

Does it work? St. John’s wort is not a proven therapy for depression. There is some scientific evidence that St. John’s wort helps in the treatment of mild to moderate depression. However, there have been two major studies that showed St. John’s wort is no better than a placebo for treating moderate depression.