What causes the need for bifocals with age?
Essentially, presbyopia is the reason for bifocals. The age related presbyopia (the presby- root means “old”) is most likely due to the hardening of the eye’s lens which makes it difficult to focus on near objects. A child’s eyes can adjust as much as 10 diopters (called accommodation) but by the age of fifty you have only about 2 diopters of accommodation. All this means is a magnification prescription for “near vision” needs to be added to your regular prescription resulting in two refraction adjustments combined into a single physical lens. Bifocals and their related brethren “progressives” are available in contact or eyeglass forms.
