In this blog post, we will discuss in great detail the multifocal and EDOF (extended depth of field) intraocular lenses that have made lens replacement surgery (also called CLE or clear lens extraction, RLE or refractive lens exchange, and a couple other names) even better over the past few years.
What is an Intraocular Lens (IOL)?
An intraocular lens (IOL) is an artificial lens that replaces your natural lens as part of a cataract or refractive lens exchange surgery. It can be made of polymethylmethacrylate (PMMA) which is a rigid IOL no longer routinely used because the incision needs to be larger. Other materials include silicone and acrylic. The current state of the art is to implant multifocal intraocular lenses that can correct your distance vision as well as your near vision.
The three basic types of intraocular lenses are monofocal, multifocal, and toric. Monofocal IOLs focus all the light at one point. If the IOL is planned to focus your vision at distance, you will need reading glasses for near objects. With monofocal IOLs you and your surgeon may decide to focus one eye at distance, and one eye at near, so you won’t be dependent on reading glasses. One eye is always blurry (the eye that is focused at near will be blurry at distance, and the eye that is focused at distance will be blurry at near), but our brains adapt well to this, so that most people don’t notice the blur. I’ve found that monovision does not cause nausea, headaches, dizziness, or difficulty going down stairs. Depth perception is only affected in very fine near work, such as threading a needle. Reading, going down stairs, golf, tennis and other sports are minimally affected. This is called “monovision” and has been done with contact lenses for decades. A 2016 ESCRS survey found 43% of IOLs were targeted for monovision* Multifocal IOLs (MFIOL) are engineered to split off some of the light to focus on distant objects and some of the light on near objects. With MFIOLs, the goal is to allow you to see well at distance and near in both eyes!
History of Intraocular Lens
The first Intraocular lenses were implanted in 1949 by Sir Harold Ridley. Dr. Ridley observed that WWII fighter pilot Gordon “Mouse” Cleaver had acrylic shrapnel from his plane canopy lodged in his eye after being shot at by German planes. The acrylic did not cause an inflammatory response as glass fragments had in other patients. Based on this observation, Dr. Ridley developed the first IOL. The company that developed the lens, along with Dr. Ridley, was called Rayner, and they still make IOLs today. IOLs are still made of acrylic and have been evolving ever since.
The first foldable silicone IOL was implanted in 1978. Foldable IOLs allow the surgeon to make a smaller incision. The smaller incisions allow more control, less trauma, eliminate sutures, cause less induced astigmatism, shorter surgical time, and quicker recovery. The first intraocular lens was approved in the United States in 1981.
State of the art cataract surgery includes MFIOLs, laser assisted cataract surgery, modern phacoemulsification (liquefaction of the lens material so it is rinsed out through microincisions), and extremely accurate lens measurement calculations to allow patients to have a painless 10 minute per eye procedure and have perfect uncorrected distance and near vision a short time after surgery. The most recent innovation is light-adjustable IOLs (LALs) which allow the surgeon to make slight adjustments to the power of the IOL with application of ultraviolet light to correct any slight prescription remaining after surgery. Pretty cool stuff!
Multifocal Intraocular Lens (MFIOL): What is a MFIOL and How Can It Benefit Me?
Multifocal IOLs (MFIOLs) are IOLs that have been designed so that some of the light is split off to focus on near objects. Designs have often included concentric rings in the center of the IOL to have alternating focus between distance and near. MFIOLs have improved substantially over the past ten years. The first MFIOL approved in the US was called the Array lens which was developed in the late 1990s. Johnson & Johnson developed the Tecnis multifocal IOL followed by their Symfony® IOL, Synergy® IOL, and Eyhance® IOL in the past few years. Alcon has similar MFIOL technology called Panoptix and Vivity MFIOL. There is a lot of debate amongst refractive cataract surgeons as to which is the best lens. My opinion is that there is no absolute best lens. Depending on a patient’s needs and wants, as well as the surgeons comfort with different technologies, the lens type can be designed to carefully fit each unique eye. The benefit to our patients is that MFIOLs can allow you to have clear uncorrected distance and near vision for the rest of your life. You will have little need for glasses ever again!
EDOF (Extended Depth of Field) Intraocular Lens: What is it and How Does it Differ from Multifocal Intraocular Lens?
EDOF lenses have been touted over the past five years to allow a broader range of near vision. Earlier designs focus the light at different ranges depending on the patient’s needs. For instance, the Tecnis lens has different powers that allow excellent focus at 10, 14, or 18 inches, but don’t focus as well at different distances. These lenses are very much in use today, and are an excellent choice depending on your visual needs. The EDOF lens called Panoptix was the first one marketed to allow better focus at an increased range of near vision, so that patients could see well at different distances to use their phone close up as well as their computer monitor that is farther away. Always discuss the lens choice at length with your surgeon. He or she will definitely have feedback amalgamated from hundreds or thousands of patients. This surgeon experience is invaluable to help you to make your best decision.
What is RLE?
RLE stands for refractive lens exchange. It is an excellent procedure for those getting closer to cataract development. If you are over 45 years old, you may be a candidate for RLE surgery. RLE surgery is performed exactly the same way as cataract surgery, but its purpose is to correct any refractive error such as nearsightedness, farsightedness, astigmatism as well as correcting your near vision with a multifocal IOL. RLE also has the added benefit of eliminating the need for cataract surgery in the future because your natural lens has already been replaced. It’s a “one and done“ procedure.
What are the Pros and Cons of RLE?
Before having any surgical procedure, it is essential that you fully understand the pros and cons of the procedure, the alternatives to a procedure, and whether or not you should even have a procedure. The good part about RLE is that it is a “one and done” procedure that fixes any refractive error in one painless 10 minute procedure. Preoperatively, the surgeon and team will perform measurements on your eyeballs so that a perfect intraocular lens can be designed to eliminate your nearsightedness, farsightedness, or astigmatism as well as decrease your need for reading glasses. When you have an RLE procedure, the artificial MFIOL lens will stay in your eye the rest of your life. It will not get cloudy like your natural lens, so you will not need future cataract surgery. Intraocular lenses have stayed in peoples eyes for many decades as evidenced by children who have had an intraocular lens inserted that remains in their eyes for the rest of their lives. Although the intraocular lens itself will not get cloudy, a frequent long term issue is that the membrane that holds the intraocular lens in place may get cloudy on the back of the intraocular lens. Fortunately this is correctable in a one minute painless laser procedure that is done in the office. The laser procedure removes the “secondary membrane” also called “posterior capsular opacification”.
Risks of any surgery include the serious and rare things, as well as the more common things that can be a nuisance. The rare things such as infection or retinal detachment happened somewhere in the one in 15,000 patients for infection, and about one in 1000 patients has a retinal detachment that will likely need additional surgery by a retinal specialist to fix. A more common risk, for multifocal IOL‘s especially, is nighttime glare. There is some trade-off when you have a multifocal intraocular lens implanted in your eyes. The multifocal intraocular lenses split off about 40% of the light for near vision. This splitting of the light tends to cause a bit of nighttime glare. Most patients adapt to this slight glare and say that it is worth the nighttime glare to have the good near vision. During the day very few patients complain of glare with the multifocal intraocular lens. This risk is specific to the multifocal intraocular lens in terms of glare. Most people have some glare with monofocal intraocular lenses also, but it tends to be slightly less. With monofocal intraocular lenses, however, you would need reading glasses if the lens is focused at distance. Other risks with Cataract/RLE surgery are that you will have slight inflammation which is controlled and eventually eliminated by postoperative steroid eyedrops. There can be other complications of RLE surgery such as bleeding, inflammation in the back of the eye, and other rare risks. It’s always important to have a full discussion with your surgeon preoperatively to understand general risks, as well as risks that are specific to your eyes. The most common moderate issue with multifocal and intraocular lenses is residual refractive error. This means that even with extremely precise preoperative measurements of your eyes, there is about a less than 5% chance that there would be enough residual refractive error (nearsightedness, farsightedness, or astigmatism) that would necessitate a secondary procedure such as LASIK or PRK to correct.
Another limitation of multifocal intraocular lens technology is that there are ranges of vision that are clear, and most of the time, ranges of vision that are not totally clear. If you want to see something extremely close, like a splinter or extremely fine print on a medicine bottle, you may need additional help in the form of over-the-counter reading glasses to boost the focusing power for very tiny images that are very near to your eyeballs. Additionally, sometimes patients say that reading something 3 to 5 feet away is a bit blurry. This is due to the fact that the multifocal intraocular lenses have concentrated the light for average reading/computer/phone use as well as distant objects greater than 10 feet away.
What Does the Future of IOL Innovation Look Like?
“Making predictions is tough…especially about the future.” -Yogi Berra
Intraocular lenses have evolved tremendously and continue to improve. The ultimate goal would be to develop an intraocular lens that replicates the lens that we have when we are children. There are many technical difficulties to overcome, but I think it’s possible. Throughout my career I have been amazed when technologies that I thought might be years away or won’t work at all have worked and been approved much more quickly than I expected.
Current MFIOL technology is fixed in place. That is, MFIOLs don’t move as our natural lens moves when we’re young. MFIOLs work because of the shape of the lens that has “built in” bifocals in a sense, but you don’t have to move your head to see near objects as you do with bifocal glasses. Ideally, an IOL would move so that you could change focus from distance to near when you want to. In order to achieve this, the IOL would need to be reliably linked to our focusing muscles, and the exertion of this slight muscular force would need to move an IOL enough to change the shape of the lens. I’ve read that the natural lens of our eyes moves about 200 µm when we exert the muscular pressure to focus on near objects. 200 µm is about 1/5 of a millimeter, or an extremely small amount. To get an artificial lens to reliably move and have a significant effect on our focusing power at near is a very tall order. However, there are multiple companies throughout the world working to achieve this breakthrough. The development of a successful fluid MFIOL may happen sooner than I think, but for now and may be the next 10 years, a static MFIOL is most likely going to be the solution for correcting distance and near vision. Current MFIOLs are excellent, improving, and will likely dominate the market for many years to come.
*Zvorničanin J, Zvorničanin E. Premium intraocular lenses: The past, present and future. J Curr Ophthalmol. 2018;30(4):287-296. Published 2018 May 18. doi:10.1016/j.joco.2018.04.00