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.
4 Most 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.