I just got my first pair of glasses with progressive lenses and the optician told me it would take a couple of weeks to adjust. So far I'm just wearing them a few minutes per day, exploring this new world of vision and when I start feeling dizzy or exhausted, I take them off.
Progressive lenses are similar to bifocals, except that the focal length of each lens changes continuously from the distance vision prescription to the reading vision prescription.
Bifocals, trifocals, reading glasses, and progressive lenses are all options for those of us over the age of 40 who have lost the elasticity in the natural lenses of our eyes. This happens to almost everyone who fails to die young. The condition is called presbyopia.
Some people choose to wear contact lenses that correct one eye for near vision and the other for distance vision. Cataract patients have new lenses implanted into their eyes, replacing the natural lenses completely and sometimes choose this “monovision” option of one eye focused for close work, the other for distance.
Implantable lenses that can change their focal length are in the developmental stages and may be an excellent replacement for natural lens.
Meanwhile, adjusting to glasses that have more than one focal length is a challenge for some. One of my friends told me that she loves her progressive lenses and was adjusted by the end of the first day. Other friends have told me they tried progressives and found them impossible.
A common observation is that people who have worn bifocals have more trouble adjusting to progressive lenses. If you go straight from single vision lenses to progressives, as I am doing, it may be easier.
The adjustment is in the brain, not the eye. Right now I'm used to two completely different pairs of single vision glasses, plus my unaided eyes. With my primary glasses, I can see to drive and do most other activities. With my computer glasses, I can read the screen without leaning in and getting massive headaches with neck pain. With no glasses, I see clearly at a close distance. When I go shopping, I wear my primary glasses, but I have to take them off to read labels.