By Mark Siegel, MD, FAAO
Before intraocular lenses (IOLs) were developed, people had to wear very thick eyeglasses or special contact lenses to be able to see after cataract surgery. Now, with cataract lens replacement, several types of IOL implants are available to help people enjoy improved vision. Discuss these options with your ophthalmologist to determine the IOL that best suits your vision needs and lifestyle.
Cataract lens replacement: How IOLs work
Like your eye’s natural lens, an IOL focuses light that comes into your eye through the cornea and pupil onto the retina, the sensitive tissue at the back of the eye that relays images through the optic nerve to the brain. Most IOLs are made of a flexible, foldable acrylic material and are about one-third of the size of a dime. Like the lenses of prescription eyeglasses, your IOL will contain the appropriate prescription to give you the best vision possible
Which lens option is right for you?
Before surgery your eyes are measured to determine your IOL prescription, and you and your cataract surgeon will compare options to decide which IOL type is best for you, depending in part on how you feel about wearing glasses for reading and near vision.
The type of IOL implanted will affect how you see when not wearing eyeglasses. Glasses may still be needed by some people for some activities.
If you have astigmatism, your ophthalmologist will discuss toric IOLs and related treatment options with you.
In certain cases, cost may be a deciding factor for you if you have the option of selecting special premium lOLs that may reduce your need for glasses.
Intraocular lens (IOL) types
Monofocal lens
This common IOL type has been used for several decades.
Monofocals are set to provide best corrected vision at near, intermediate or far distances.
Most people who choose monofocals have their IOLs set for distance vision and use reading glasses for near activities. On the other hand, a person whose IOLs were set to correct near vision would need glasses to see distant objects clearly.
Presbyopia is a condition that affects everyone at some point after age 40, when the eye’s lens becomes less flexible and makes near vision more difficult, especially in low light. Since presbyopia makes it difficult to see near objects clearly, even people without cataracts need reading glasses or an equivalent form of vision correction.
Multifocal lenses
This newer IOL type reduces or eliminates the need for glasses or contact lenses.
With the multifocal lens, a series of focal zones or rings is designed into the IOL. Depending on where incoming light focuses through the zones, the person may be able to see both near and distant objects clearly.
The ability to read and perform other tasks without glasses varies from person to person but is generally best when multifocal IOLs are placed in both eyes.
It usually takes 6 to 12 weeks after surgery on the second eye for the brain to adapt and vision improvement to be complete with this IOL type.
Considerations with multifocal IOLs
For many people, these IOL types reduce but may not eliminate the need for glasses or contact lenses. For example, a person can read without glasses, but the words appear less clear than with glasses.
Each person’s success with these IOLs may depend on the size of his/her pupils and other eye health factors.
Side effects such as glare or halos around lights, or decreased sharpness of vision (contrast sensitivity) may occur, especially at night or in dim light. Most people adapt to and are not bothered by these effects, but those who frequently drive at night or need to focus on close-up work may be more satisfied with monofocal IOLs.
Toric IOL for astigmatism
This is a monofocal IOL with astigmatism correction built into the lens.
Astigmatism is an eye condition that distorts or blurs the ability to see both near and distant objects. With astigmatism, the cornea (the clear front window of the eye) is not round and smooth (like a basketball), but instead is curved like a football. People with significant degrees of astigmatism are usually most satisfied with toric IOLs.
Protective IOL filters
IOLs include filters to protect the eye’s retina from exposure to UV and other potentially damaging light radiation. The cataract surgeon selects the filters that will provide appropriate protection for the patient’s specific needs.
Other important cataract lens replacement considerations
People who have had refractive surgery such as LASIK need to be carefully evaluated before getting IOLs because the ability to calculate the correct IOL prescription may be affected by the previous refractive surgery.
