A hardening of the lens of the eye associated with aging, other medical conditions and certain drugs causes presbyopia, according to Mayo Clinic. People with the condition cannot focus on close-up images, as the lens is no longer flexible enough to change shape.
The lens of the eye is normally flexible enough to change shape with the help of the muscle that surrounds it. In a person with presbyopia, however, the muscle does not contract and relax properly, states Mayo Clinic. Most people experience some level of presbyopia after the age of 40, and certain drugs such as antidepressants, antihistamines and diuretics may lead to early onset of the condition. People with diabetes, multiple sclerosis or cardiovascular diseases are also at a higher risk of developing premature presbyopia.
Doctors diagnose presbyopia through eye exams that include dilating patients' pupils to better evaluate the inside of their eyes, according to Mayo Clinic. They also run a series of tests with different lenses to gauge patients' abilities to focus on nearby and distant objects. Doctors typically recommend corrective lenses such as prescription reading glasses, bifocals or trifocals to treat people with presbyopia, or patients may choose contact lenses. Other treatment options include surgery to reshape the cornea, such as LASIK, and lens implants.