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What is an intraocular lens (IOL)?

An intraocular lens (IOL) is a manmade lens that is placed inside the eye after cataract surgery or custom lens replacement.  

Please note than an IOL is not the same as an EVO ICL, which is a different lens placed in front of the natural lens while leaving the natural lens in place to correct nearsightedness with or without astigmatism.  Once a natural lens has been removed, typically because it has become a cloudy cataract or because the natural lens has lost its flexibility in a process called presbyopia, an IOL is usually placed.

How does an IOL differ from the natural lens we are born with?

The natural lens we are born with is also called the crystalline lens.  It is clear and flexible when we are young.  The natural lens’s flexibility, also called accommodation, is why young people who have good distance vision do not also need reading glasses for help up close.  For young people who are nearsighted and need “minus power” glasses or contacts to see far away, they do not need a separate bifocal segment to see up close, because the natural lens is accommodating – pulling the focal point inward.

Over time, the natural lens becomes stiff, typically in our 40s, and that results in the inability to focus from distance to near. This loss of range is called presbyopia.  Presbyopia means “old eye” in Greek. Those who have always had perfect vision everywhere begin to need reading glasses for up close or hold objects further away to see them.  Those nearsighted people who have always worn their glasses or contacts may now have to either add a bifocal or remove the glasses to see up close.  Presbyopia is normal and inevitable whether someone has had LASIK or EVO ICL in the past or not, and while there are a few prescription eyedrops available that can help, they have not been a major success due to limited effectiveness, risk profile and side effects.

Call us at 713-893-2020 or contact us to make an appointment if you want to discuss how best to help your vision. 

Whether you consider a custom lens exchange (CLR) at this time of natural lens dysfunction or wait until the natural lens becomes cloudy and you need cataract surgery, it will almost always make sense to place an IOL during that surgery.

What kinds of IOLs are available?

Most IOLs are either acrylic plastic or silicone. Both materials work well with the eye tissues long-term.  Neither material generates a foreign body rejection response, due to the eye’s unique properties.  In fact, a British ophthalmologist, Sir Harold Ridley, noticed that a British World War II pilot’s eye tolerated a fragment of acrylic from his airplane, prompting Sir Ridley to ultimately be the first surgeon to place an IOL after cataract surgery.

There are many types of IOLs, and it is easy for patients to feel overwhelmed by the many options.  We recommend seeing a surgeon who has specific subject-area expertise in IOL selection.  Dr. Bennett Walton has specific expertise in the area of advanced cataract surgery IOL personalization and is a consultant, advisor, and clinical trial surgeon to both the “Big 4” ophthalmic companies who design IOLs and IOL-specific companies.

Range of Vision IOLs

Trifocal or bifocal lenses have multiple focal points. These lenses give the biggest range of vision from distance to near.  In general, eyes need to be quite healthy to enjoy the benefit of these lenses.  Unlike bifocal or trifocal glasses, they are easier to use in that you do not have to move your head or neck to get things into focus.  Brand names in this class include Clareon Panoptix, Finevision, Tecnis Synergy, Tecnis Multifocal and others.  They are available in astigmatism-correcting “toric” versions, since correcting astigmatism is an important part of crisp vision.

Extended depth-of-focus (EDOF) IOLs have an extended focal range.  Astigmatism correction may also be built-in.  Some models in this category have easier nighttime vision than others.  Brand names include Clareon Vivity, Tecnis Symfony, Apthera and others.

Each of these lenses has a different vision profile, and selecting the best one for an individual patient’s eyes requires expertise.

“I highly recommend working with Dr. Walton. My experience with him for two LK procedures and a cataract surgery/lens replacement (just yesterday) has been outstanding. Dr. Walton’s expertise and commitment to care cannot be beat!”

Bonnie M.

Adjustable IOLs

An adjustable IOL has one focal point, but unlike every other lens, it can be adjusted after surgery with a non-invasive light treatment. The accuracy is the highest among IOL technologies, since we wait for the eye to heal and then re-measure based upon what your eye is actually seeing.  It can treat nearsightedness, farsightedness, or astigmatism within certain ranges.  Special glasses are provided to be worn until the adjustment process is finished.  The brand name is the Light-Adjustable Lens, and Dr. Walton has particular expertise with the LAL as a clinical trial surgeon and investigator.

Toric Monofocal IOLs

These IOLs have a narrow focal range that will require more pairs of reading glasses to see different focal points when aimed for distance, but they do have built-in astigmatism correction.  Brand names include Clareon Toric, Tecnis Toric, Envista Toric and others.

Basic Monofocal IOLs

Basic IOLs are still made of excellent material. However, they give a narrow focal range and do not correct astigmatism to achieve the best clarity if needed.  There are many brand names from many companies.

What is astigmatism, and why does it matter for cataract surgery?

Astigmatism refers to the focal power of the eye being not like a soccer ball or a basketball – with the same curvature in every measurement direction – but instead more like an American football – with a tighter curvature in the “quarterback grip” direction, and with a flatter curvature in the vertical kicking direction. For another example, think of the difference between seeing your reflection in an equally round soup spoon, which gives a more balanced reflection as if there is no astigmatism, versus a normal spoon, which has an oval shape that warps the reflection of part of your face.

Some people have never needed astigmatism correction in the past, but will at the time of or after cataract surgery. This is because removing the natural lens changes the overall optics of the eye. There are many examples in which people’s natural lens offsets or negates built-in astigmatism from the cornea, or windshield of the eye.  Then, when the natural lens or cataract is removed, the total astigmatism is now unbalanced, making the vision blurry.  This is typically better shown in your various measurement pictures, which Dr. Walton will review at your cataract evaluation.  Most people who have had astigmatism correction in their glasses or contacts in the past will also need it at cataract surgery to see their best.

Should I have my astigmatism corrected with an IOL or with the laser at the time of laser cataract surgery?

Dr. Walton will discuss your best option with you. In general, it has to do with the amount of astigmatism, how “regular” it is, and the orientation of the steep axis of the eye.  It will make more sense when Dr. Walton can show you the images of your eye during a cataract evaluation.

Astigmatism correction is important for sharp vision, but astigmatism correction alone does not restore a full range of vision.

How is an intraocular lens (IOL) placed?

Dr. Walton will insert the IOL folded through a small incision and allow it to unfold inside the eye.  IOLs are placed behind the colored iris tissue in the middle of the eye. This technique is minimally invasive and normally requires no stitches for the cataract or custom lens replacement surgery.

Do intraocular lenses (IOLs) have side effects?

All IOLs are different from the natural lens in a few ways.  They are thinner and smaller in diameter than the natural lens, making easier to fold and insert in a minimally invasive fashion.  The refractive index of the material – which is how it focuses light – is different from the natural lens.  All IOLs, even the basic monofocals, have some optical side effects, and some models have more than others.  Typically, optical side effects are dysphotopsias, which could refer to glare, halo, starburst, or other optical phenomena.  Some people notice these more than others, and the symptoms typically improve over time as the brain begins to adapt to the new, different visual world.  Again, these are reasons why making a wise IOL choice in the first place is important.

Can IOLs be swapped or changed later in life?

In general, it is not recommended to change out an IOL later unless there is a compelling health or visual reason.  The eye heals by shrink-wrapping the new IOL into place, which means an IOL exchange requires opening well-healed tissue inside the eye.  Dr. Walton is experienced in IOL exchange surgery, but the goal of a well-planned cataract or custom lens replacement surgery is to make a wise choice the first time.  The IOL placed is meant to provide the vision for the rest of a lifetime.

What about eye changes over time?

All body tissues grow and change, and the eye is no different.  However, after IOL placement with cataract or custom lens replacement surgery, the biggest source of change has already been removed:  the natural lens.  Changes tend to be small and over long periods of time.

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