Presbyopia is caused when the eye gradually loses its ability to see objects up close. It happens to everybody from around the age of 40 and gradually continues from then on. The main reason for it occurring is that the lens in the eye becomes less flexible and harder to change shape, and so makes close objects look blurred. As the changes happen so gradually, the effects are often not noticed immediately.  But over time, headaches may occur and reading may become more difficult – unless you hold a book further from you. Presbyopia is easily corrected using reading, progressive, or bifocal glasses. Contact lenses are now also available.