Reading Speeds Tell Us about Adaptation to Multifocal IOLs

One of the most interesting things about the multifocal intraocular lenses (IOLs) used in cataract surgery and presbyopia surgery is how the brain learns to select the proper image from among the multiple images these lenses cast on the retina.

Multifocal lenses allow you to see objects at different distances by having a number of focus zones, each dedicated to a particular task, some focusing on close objects, others on far objects, and often balanced for both bright and low-light conditions. Although this solution ensures that for most objects there will always be a focal zone that focuses light from the object you're looking at onto the retina. However, it also means that there will be a number of unfocused images of the same object on the retina at the same time. Your mind just learns to sort them out, the sort of visual trick it already does every day, although not everyone adapts well to the new visual system. One question people have about the process is "How long does it take for the brain to adapt?"

Recent research suggest that it may take 18 months or longer for the brain to fully adjust to using the lenses. Although people get full visual acuity (on average 20/40 vision) by 6 months after surgery, it does not mean that their eyes and brains are fully adapted at this point. Instead, it seems that their eyes are continuing to adjust. A recent study looking at 25 patients who received either the Tecnis or Acrysof ReSTOR at 6, 12, and 18 months after bilateral implantation of the IOLs. The study looked at visual acuity and reading time. Although visual acuity showed no significant deviation over the follow-up period, reading speed continued to increase over the entire follow-up period, which indicated to researchers that patients' brains were continuing to adapt to the novel visual system over the entire study period.

If you are considering a multifocal IOL for correction of presbyopia or during cataract surgery, you should talk about the adaptation period for IOLs with your ophthalmologist. Please call or email us today to contact a local ophthalmologist experienced in cataract surgery.