IOL Focusing Power

The most common type of lens used with cataract surgery is called a monofocal IOL. It has one focusing distance. It is set to focus for up close, medium range or distance vision. Most people have them set for clear distance vision. Then they wear eyeglasses for reading or close work.

People who want to be less dependent on eyeglasses might want to consider other lenses known as presbyopia-correcting IOLs. Three types— multifocal, accommodative, and extended depth-of-focus IOLs—offer different focusing powers within the same lens. These IOLs reduce your dependence on glasses by giving you clear vision for more than one set distance. Here’s how they work.

• Multifocal IOLs. Provide both distance and near focus. The lens has several rings or zones set at different powers. With this design, you are actually using both near and far vision at the same time. However, your brain learns to automatically select the right focus for what you want to see.

• Accommodative IOLs. Similar to your eye’s natural lens, this type of IOL moves or changes shape to bring objects into focus at different distances.

• Extended depth-of-focus lenses. Like multifocal lenses, extended depth-of-focus (EDOF) lenses sharpen vision up close and far away. But EDOF lenses have only one corrective zone, which “extends” to cover both distances. This may mean less effort to re-focus between distances.

 

Setting Your IOL’s Focusing Power

Your eye surgeon will take measurements in and on your eye before surgery. These measurements are used to decide the correct power of IOL to use.

Things that are measured include your:

• refractive error (nearsightedness, farsightedness, astigmatism or presbyopia)

• pupil size and function

• cornea curve and shape

• eye length from cornea to retina (light-sensitive tissue in the back of the eye)

How an IOL Is Put in Your Eye

• Your eye surgeon will numb your eye with a topical or local anesthesia.

• He or she will make a few tiny incisions near the edge of the cornea. These incisions allow your surgeon to work inside the eye.

• Using special instruments, your ophthalmologist will break up the center of the eye’s natural lens. Then those pieces are gently vacuumed out through one of the incisions. The “capsular bag” that holds your natural lens in place is not taken out.

• The IOL is folded and inserted through the incision. It is placed in the “capsular bag,” where it unfolds.

• The tiny incisions in your eye are usually “self-sealing,” meaning you will not need stitches.

It could take 6 to 8 weeks after surgery to be able to focus fully at all ranges. Basically, your eye has to relearn how to focus at various distances to see clearly.

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Who Might Not Benefit from Presbyopia-Correcting IOLs?

With these IOLs, there may be some visual side effects. For instance, your vision may be not be sharp in dim light or fog. You may also notice glare and rings (halos) around lights. Pilots, night drivers or those who spend a lot of time in front of the computer may find these side effects cause problems.

Those who already have eye disease are more at risk for poor visual outcomes from these IOLs.

Your ophthalmologist can help you choose a lens based on the health of your eyes and what you want and need from your vision.

 

Talk with Your Ophthalmologist About Your Vision Needs

There are benefits and drawbacks to surgery, eyeglasses and contact lenses. As you explore how to correct your vision, consider your vision needs and expectations. Your ophthalmologist will explain IOL options for you in more detail.