If you're having trouble with your vision, then you need to go for an eye exam. This might happen as part of your regular checkups at the doctor. However you need to see a vision specialist if your doctor thinks you might need glasses.
You might see an ophthalmologist, optometrist, or an optician. An ophthalmologist is a doctor who treats all vision problems and also does eye surgery. An optometrist is a licensed professional who specializes in eye exams and tells you the right prescriptions for eyeglasses and contact lenses. Opticians are the ones who make or sell eyeglasses and contact lenses according to an ophthalmologist or optometrist's prescription.
In your eye exam, you'll probably be asked to read from an eye chart, which contains letters in different sizes. You also might be asked to look at some close text, like reading from a book. These tests will brief you about how well you see from close and from far away. If you require glasses or contact lenses then there is a special device that will let you try a few different prescriptions until you find the one that will give you the clearest vision. It is like a big pair of glasses in which a bunch of different lenses can be switch in and out rapidly. The person doing your eye exam may switch between two different lenses and say, "this one is clear or this?" You have to say which one looks clearest. If you're not sure, say so. Keep in mind that you get the right prescription so your vision will be excellent!
