Optometrists and ophthalmologists check your near vision with several basic eye tests. The exam for reading glasses only takes about a half hour to an hour. If you need a near correction, when the testing is complete you will have a written prescription for eyeglasses that will help you better see small print and fine detail.
Reading glasses correct near vision. Most people start wearing reading glasses around the age of 40 to 45 years, the time when your eyes start to lose some of the ability to focus up close because of the hardening of the lens within the eye. This is called presbyopia, and is different than distance correction (for nearsightedness) or closer-distance correction (for farsightedness).
Presbyopia literally means "old vision." It is not a disease but a part of the normal process of aging. You can be farsighted, not being able to see things nearby, or nearsighted, not able to see far away, and still need a reading prescription with either type of problem. Some people with presbyopia may only need glasses for reading or close work, with only minor or no distance correction.
During your vision exam, your doctor will do several tests. Even if you just need reading glasses, your doctor will check your distance vision with the chart on the wall, called the Snellen chart. With each test, the doctor will have you cover one of your eyes, and then the other, and ask you to read the furthest line down on the chart that is clear. The doctor will then use a Near Vision Reading Card, which you will hold in your hand. The Near Vision Reading Card is usually made up of rows of numbers that get smaller and smaller down the card. As you cover each eye, you will be asked to read the clearest line of numbers, usually from the left side of the card to the right.
The doctor will note how far you can read down the card clearly, and record your preliminary screening. Then you will be tested with an instrument called a phoropter, which is put in front of your eyes and shows you a series of lens choices. The doctor will ask you which of two lenses in each choice looks clearer, making a final determination of your reading correction.
If you are starting to hold things out further, at arm's length, to read, then it is probably time for you to be checked for a prescription for reading glasses. If you already wear glasses for distance, a reading exam will yield a bifocal prescription.
The bottom portion of the bifocal is usually written as ADD on the paper prescription. If you do not wear any type of distance correction, the doctor will sometimes write PLANO for the top part of the prescription, and the strength of your reading glasses in the bottom, ADD, section. You may want the whole lens in your glasses to carry your reading prescription. Reading glasses usually have a correction power starting at +1.00 and go up increments of +.25 or +.50.
Most doctors recommend an eye exam every one or two years. The tests done during an ophthalmic exam check more than just your prescription. The doctor looks for eye diseases, such as glaucoma, and also checks for other health problems that are visible by looking inside your eyes, such as hypertension and diabetes.
Many department and drug stores now sell reading glasses with prescription-power lenses. While you may find a pair that works well for you, the prescription will not be as accurate for your particular case as in glasses purchased through a doctor's office, optical chain or lab.