Presbyopia has to do with the natural aging process of the human crystalline lens. In a young patient, the crystalline lens is flexible and able to become rounder and more steep/ more powerful in order to bring near objects into focus. This process is called accommodation. Between 40 and 50 years of age, the crystalline lens begins to lose its ability to accommodate. This is a natural process which occurs in every patient without exception.

Normally sighted patients then require reading glasses to see nearby objects in focus. Longsighted patients then need both distance and reading glasses. Sometimes, patients with a small amount of shortsightedness can remove their distance glasses to be able to read up close. Patients with higher amounts of shortsightedness require weaker glasses in the near (bifocals) in order to read at a comfortable distance. Presbyopia can also be treated with an excimer laser, however, this is not yet a routine procedure since research is still in its early stages.