Our eye's ability to focus reaches its peak at around 12 years old, then slowly declines with every year thereafter. By the time we reach ages 35 to 45, many of us begin to notice we're holding reading material so far away that our arms seem too short. It's called presbyopia, the age-related vision change that occurs as your once-flexible lens becomes harder and less clear. Here's what to do when you notice that your vision is starting to get bad.

Schedule for an eye check-up. Schedule an eye examination to review the health of your eyes and the overall functioning of your visual system. This includes tests for how well your eyes focus on objects, both far and near, and how well they work together for depth perception.

Don't make excuses, like telling yourself you can see okay so long as the lighting is bright enough or you're feeling okay. It is true that your vision may be sharper in the bright light of a sunny day since the pupils constrict and increase your depth of focus. But you also deserve to see well indoors, in the soothing light of your room, or when walking the streets at night.

If you notice yourself squinting to clear up blurry letters, you're doing yourself no youthful favors. Constant squinting deepens the lines around your eyes, making you look older. Squinting in bright sunlight is no better. Wear sunglasses to help preserve the smooth appearance of your face around your eyes. Sunglasses will also help to prevent cataracts, which can be caused by sun damage.

A new pair of glasses or a specially designed pair of contact lenses will restore your ability to see close-up again. Your own best option may be bifocals, bifocal contact lenses, or a pair of reading glasses. Check with your eye professional for recommendation.

Although not all eye professionals agree, some advocate exercising the muscles in the eyes the same way you exercise the other muscles in your body. Eye experts suggest the following tips for those who want to keep their visual system functioning well.

1. As you go about your daily life, practice tracking moving objects and following things. Computer games help with this, but take frequent breaks.

2. Shift your gaze often. Fix your sights on something in one corner of the room, then the other in a rhythmic way. Look here and there. Focus near, then focus far. When you're reading, look across the room every 2 minutes.

The very best thing that you can do to keep your eyes young and your vision sharp is to practice prevention. Investing a little attention in your eyesight now will go a long way toward keeping it healthy in the future. Here's what the experts recommend.

1. Wayne Fung, M.D., an ophthalmologist at the California Pacific Medical Center in San Francisco, recommends munching on fruits and vegetables that are rich in beta-carotene. The beta-carotene is important for good eye health, and eating fruits and vegetables adds fiber, which is important to your overall health. Good choices include papaya, mango, kale, Swiss chard, pumpkin, broccoli, and spinach, he says.

2. As your eyes age, the protein material in your lens may begin to cloud, subtly at first, like adding drops of milk to a glass of water, one at a time. Getting annual eye examinations during your middle-aged years will diagnose cataracts early, before they begin to significantly interfere with your driving ability, reading, and everyday living.

3. Don't let blindness sneak up on you. Perhaps the most important reason for regular eye exams is glaucoma screening. When pressure builds behind the eye, damage can occur to the optic nerve, which can lead to blindness. Since there are no symptoms, an examination is your only path to early detection. If you have suffered a significant eye injury at any time during your life, or if you have blood relatives with glaucoma, you're at higher risk for developing glaucoma during middle age.

4. As you lead your busy, active life, make sure that your eyes have the protection they need. Wear impact-resistant sunglasses or safety glasses that protect your eyes from injury as well as guard against ultraviolet rays. Wear a wide-brimmed hat while gardening, golfing, or watching sporting events in the sun.