How Visual Neuroadaptation Allows Adjusting To Cataract Surgery Side Effects

Getting cataract surgery is quite exciting. It’s quite remarkable how much vision can be improved over cataracts. But after the procedure, vision is corrected in a slightly different way than before. Because of this, weird phenomena and side effects can appear in vision.

Multifocal Lenses

Multifocal lenses (also known as lifestyle lenses) are great! They really open up a door to all sorts of possibilities to live a life unencumbered by glasses or contact lenses. But nothing in life is ever perfect and multifocal lenses aren't an exception. While these lenses work incredibly well to obtain this awesome glasses-free vision, there are a few symptoms that require some adjusting. While these symptoms are vastly improved from previous versions of multifocal lenses, they still exist and are still worth knowing about.

The most common symptom people have with multifocal lenses is the observation of halos and starbursts around lights. Multifocal lenses simultaneously correct for up close vision and distance vision. When light enters the eye, it gets focused at the same time for both distance and up close regardless of where you are looking. Thus, if you are looking in the distance, the up close light will be more blurry and cause a halo or starburst around lights. This is typically noticed at nighttime and can cause more difficulty with driving at night in the beginning. Gradually, however, as the brain adjusts to these new lenses, this haloing effect diminishes until you kind of forget that it is there.

Rarely, some people with multifocal lenses may also notice a decline in their perception of contrast. This is often described as a seeing a "film" over their vision. This issue was a larger deal with older types of multifocal lenses and fortunately has become much less common with modern versions of multifocal lenses.

Getting a multifocal lens or lifestyle placed with your cataract surgery or refractive lens exchange is a fantastic way to correct your vision. However, it is just good to know that there will be a little bit of adjusting required after the procedure.

Crescents After Cataract Surgery

But even with a standard monofocal lens, one can still notice some weird side effects after cataract surgery. Seeing crescents out in your peripheral vision is one of these weird things. The good news, however, is that this is normal and not any indication of problems with the new lens.

The new lens that gets placed after cataract surgery is not as large as your own natural lens / cataract that gets removed. This new artificial lens is also much much thinner. Because of this, light hitting the peripheral part of the lens behaves differently. As light hits the edge of the lens, it doesn’t pass right through. Instead that light bounces off into a separate direction. Because of this, there is a spot on the retina in the periphery that doesn’t receive the same amount of light. This creates a crescent or sometimes the feeling of having “blinders” on.

_{Crescent shape; Image by xlibber, CC BY 2.0, via Wikimedia Commons}

This crescent effect is more noticeable right after the surgery rather than later down the road. So if you see these crescents after your cataract surgery, not to worry. This is a normal phenomenon which gradually improves over time.

Over time, the brain learns to adjust to the new way of seeing after cataract surgery and compensate for this effect. Also, as this new lens becomes secured in place, additional light gets scattered at the peripheral lens to fill the retina. Both of these combine to allow for this crescent effect to phase away after surgery.

This adjustment to the crescents and to the halos with mutifocal lenses is called visual neuroadaptation.

Visual Neuroadaptation

_{Training the brain; Image by Tumisu, CC0, via Wikimedia Commons}

The brain is capable of wonderful things; it's what makes us human. It allows us to think, to create and most importantly allows us to see. How is it capable of all these things? It learned how to over time.

Most of this learning happens when we are children. But the learning doesn’t stop there. Learning continues well into adulthood. But learning isn’t just for absorbing new material. Learning also allows us to adjust to the environment and focus on the things which really matter. This type of learning is called neuroadaptation.

There are lots of stimuli that we encounter that the brain doesn’t need to focus on. If you wear a wristwatch for instance, the brain learns over time that it doesn’t need to focus energy on feeling the wristwatch on your wrist. And so, gradually over time you forget that you are even wearing a watch (that is until you want to check the time).

The same thing happens with vision. The eyes only exist to send vision information to the brain. It is up to the brain to process that information and create the visual scene that we see before us. If there is unnecessary information in your vision, the brain gradually processes that out of the “scene”. This is what happens to help make floaters disappear from your vision. This is what happens to halos after cataract surgery (and also after lasik and with contact lenses). As the brain learns that these halos aren’t necessary to see, it gradually subtracts them from your interpretation of vision through visual neuroadaptation.

It is a cool process and really remarkable what the brain is capable of. The one downside is that it is slow. It can take months to even years for the brain to fully adjust. But it is cool to see that your vision constantly gets “smarter” over time.

Be sure to check out Adjusting And Training Eyes After Cataract Surgery on EyeMountain.com

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