Presbyopia is caused by an age-related process and is generally believed to stem from a gradual loss of flexibility in the natural lens inside your eye. The eye's lens stiffens with age, so it is less able to focus when you view something up close. The result is blurred near vision. (Illustration: Varilux) These age-related changes occur within the proteins in the lens, making the lens harder and less elastic with the years. Age-related changes also take place in the muscle fibers surrounding the lens. With less elasticity, the eye has a harder time focusing up close. Other, less popular theories exist as well.   PRESBYOPIA SYMPTOMS AND SIGNS When people develop presbyopia, they find they need to hold books, magazines, newspapers, menus and other reading materials at arm's length in order to focus properly. When they perform near work, such as embroidery or handwriting, they may have headaches or eyestrain, or feel fatigued. Presbyopia is different from astigmatism, nearsightedness and farsightedness, which are related to the shape of the eyeball and caused by genetic factors, disease, or trauma.   © 2005-2008 VISIONFOREGOLFING.COM AND TIMED DESIGNS, INC. ALL RIGHTS RESERVED