When an eye has an irregular shape, it keeps light from focusing correctly on your retina (a light-sensitive layer of tissue in the back of your eye). This is called a refractive error, and it can make it difficult to see clearly.
Refractive errors are the most common type of vision problem. More than 150 million Americans have a refractive error — but many don’t know that they could be seeing better. That’s why eye exams are so important.
If you have a refractive error, your eye doctor can prescribe eyeglasses or contact lenses to help you see clearly.
Four Common Types of Refractive Errors
Presbyopia may seem to occur suddenly, but the actual loss of flexibility takes place over a number of years. Presbyopia usually becomes noticeable in the early to mid-40s. Presbyopia is a natural part of the aging process of the eye. It is not a disease, and it cannot be prevented.