Do you know the difference between normal changes in vision that occur with age and abnormal changes caused by age-related eye disease? Here are some answers.

The main age-related vision problem is presbyopia, or the slow loss of ability to see close objects. This is a normal part of the aging process, typically beginning after age 40, and can be corrected with reading glasses.

Age-related macular degeneration (AMD) is the top cause of legal blindness for people over 50 in the western world. AMD afflicts 25 million to 30 million people worldwide.

A clear lens in the eye focuses light. This lets the eye see images sharply. With age, the lens slowly becomes cloudy. The cloudy lens is a cataract. A cataract scatters light and makes it hard for the eye to focus.

A cataract is a clouding of the eye's lens, a clear, soft structure behind the pupil that works much like a camera lens. The top cause of cataracts is aging. In fact, more people over 70 have cataracts than not.

Glaucoma is an eye disease that can cause blindness. It usually begins when pressure builds up in the eye. If caught early, it can usually be controlled. But it often has no symptoms, so you need regular eye exams.

Treatment can prevent or limit vision loss from glaucoma. The goal of treatment is to control glaucoma by lowering eye pressure. Medicines and procedures may also help.

Presbyopia is the loss of close-up focusing. With age, the lens in the eye hardens and cannot change its shape as easily. It then can’t focus clearly on close objects. This makes them look blurry.

As your eyes age, their lenses become less flexible, and they slowly lose their ability to focus. It's an ongoing, lifelong process called presbyopia, which you begin to notice between ages 40 and 45.

The retina is the inside lining of the eye. It turns light into nerve signals. These signals are then sent to the brain where they become the images you see. The retina may be torn or detached due to aging, an eye injury, or other problems. Tears and detachments are painless.

Depending on your retinal damage, your doctor may use one or more procedures to treat the problem. Some treatments can be done in your eye doctor’s office. Others require surgery in a hospital or surgery center.

To be comfortable, your eyes need to be lubricated, or bathed, with tears. But if your eyes don’t produce enough tears, the surface gets irritated. This is known as “dry eyes.”

Artificial tears are the most common treatment for dry eyes. If they don’t relieve your symptoms, your eye doctor may put in plugs or do surgery to stop the draining and increase the tear film.

The macula is the central portion of the retina. In macular degeneration, the cells in the macula gradually cease to function, causing a person's central vision to become fuzzier and eventually make it impossible to read, drive or do close-up work. It can affect one or both eyes.