Presbyopia is age-related far-sightedness caused by the loss of lens elasticity. It usually begins between the ages of 40 and 50, initially causing blurred vision, difficulty seeing in dim light, and eye strain. Reading glasses or glasses with progressive lenses are the most common correction for presbyopia, but surgical options are also available.

In young eyes, the lens is able to focus light from objects at different distances by a process called accommodation. During accommodation, muscles surrounding the lens contract, causing the lens to change shape and increasing the focusing power of the eye. This allows dynamic clear vision at near and far distances. With increasing age, the lens becomes stiffer as the structural crystallin proteins become misfolded. This increased lens stiffness limits the eye’s ability to adjust its focus for reading or other tasks that require clear vision at near distances.