Author: Tanner Ferguson, 4th year medical student, University of South Dakota Sanford School of Medicine
Presbyopia is the age-related stiffness of our lens that reduces our ability to accommodate, or focus on near objects1,2. Normally, people are born with a clear and flexible lens. It is helpful to think of the lens as the “reading” lens with two functions: vision clarity and near vision (accommodation). These both may be compromised as we age (cataracts and presbyopia, respectively).
When the eye accommodates, the pliable, crystalline lens becomes more rounded to increase its refractive power for closer viewing. An object at distance has light rays that are nearly parallel and do not require as much refraction to focus the rays on the retina. Light rays from a near object diverge and require a more converging (convex) lens to shorten the focal length and bring a near object into focus1,2. The figures below illustrate normal accommodation and presbyopia.
As we age, our ability to focus on near images is diminished due to reduced lens flexibility1. This typically starts around age 40 but worsens over the next 10-20 years and varies patient to patient. Individuals often first complain of difficulty reading after a long day of “near work” (e.g. working on the computer) or indicating they require increased lighting to read. They may also have discovered the first line treatment, which is using “cheaters” or reading glasses available over-the-counter that assist with focusing on near objects.
- Glasser A, Campbell MC. Presbyopia and the optical changes in the human crystalline lens with age. Vision Res. 1998;38(2):209-229.
- Atchison D. Accommodation and presbyopia. Ophthalmic and Physiological Optics. 1995;15(4):255-272. doi:10.1016/0275-5408(95)00020-E.