INTRA-OCULAR LENSES (IOLs)
Before intra-ocular 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 eye doctor to determine the IOL that best suits your vision needs and lifestyle.
CATARACT LENS REPLACEMENT: HOW IOLs WORK?
Which lens option is right for you?
Before surgery your eyes are measured to determine your IOL prescription, and you and your eye doctor 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 Eye M.D. 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.
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.Some who choose monofocals decide to have the IOL for one eye set for distance vision, and the other set for near vision, a strategy called “monovision.” The brain adapts and synthesizes the information from both eyes to provide vision at intermediate distances. Often this reduces the need for reading glasses. People who regularly use computers, PDAs or other digital devices may find this especially useful. Individuals considering monovision may be able to try this technique with contact lenses first to see how well they can adapt to monovision. Those who require crisp, detailed vision may decide monovision is not for them. People with appropriate vision prescriptions may find that monovision allows them see well at most distances with little or no need for eyeglasses. 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.
Astigmatism and cataract? A toric IOL can fix both
Most people with cataracts want not only to have clear vision after cataract surgery, but freedom from eyeglasses as well. One thing that can prevent that from happening is residual astigmatism after surgery.
Astigmatism is very common before and after cataract surgery. Almost one in three people who are candidates for cataract surgery in the United States have at least 1.0 diopter (D) of astigmatism, which is enough to cause noticeably blurred vision without eyeglasses or contact lenses.
One study of refractive errors found that 29 percent of the U.S. population has between 1.0 and 2.0 D of astigmatism, 6.5 percent has between 2.0 and 3.0 D, and 2.2 percent has at least 3.0 D. These findings suggest nearly four out of 10 Americans have a significant amount of astigmatism.
In the past, intraocular lenses (IOLs) used in cataract surgery could not correct astigmatism. Some astigmatism could be corrected if the cataract surgeon chose to make incisions in the cornea during cataract surgery — a procedure called limbal relaxing incisions (LRI). Unfortunately, the LRI procedure can correct only limited amounts of astigmatism, and sometimes outcomes are unpredictable.
Thankfully, special intraocular lenses (called toric IOLs) have been developed to more predictably correct astigmatism during cataract surgery.
How Toric IOLs Work
Like toric soft contact lenses for astigmatism, toric IOLs have different powers in different meridians of the lens to correct the asymmetric power of the eye that is characteristic of astigmatism.
Cataract surgery with a toric lens implant (IOL) is essentially the same as cataract surgery with a conventional IOL, but with a couple of important differences.
Prior to surgery, measurements are taken to enable cataract surgeons to choose the most beneficial toric IOL power and the required orientation of the implant in the eye to correct the astigmatism successfully.
Toric IOLs have special markers on the peripheral parts of the lens that enable the surgeon to see the orientation of the astigmatism correction in the lens. Once the toric IOL is implanted in the eye, the surgeon then rotates the lens so the astigmatism correction is properly aligned for best results.
Use of a toric IOL during cataract surgery does not increase the risk of common cataract surgery complications, but a misaligned toric IOL can cause blurred vision that cannot easily be corrected with eyeglasses or contact lenses.
The toric correction is not included in the newer presbyopia correcting IOLs, like Toric Symfony.
Simulation of vision throughout life and with correction of cataract with different types of lens implants
Multifocal or accommodative lenses
These newer IOL types reduce or eliminate the need for glasses or contact lenses. In the multifocal type, 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 design of the accommodative lens allows certain eye muscles to move the IOL forward and backward, changing the focus much as it would with a natural lens, allowing near and distance vision. The ability to read and perform other tasks without glasses varies from person to person but is generally best when multifocal or accommodative 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 either of these IOL types.
Considerations with multifocal or accommodative IOLs
For many people, these IOL types reduce but do 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. People with astigmatism can ask their eye doctor about toric IOLs and related treatments. 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.
Simulation of vision with Astigmatism with correction of cataract with different types of lens implants
The latest addition to the TECNIS Family of IOLs offers new optical technology for providing an Extended Range of Vision.
Traditional IOL solutions for treating presbyopia include Multifocals and Trifocals, which work on the principle of simultaneous vision by splitting light into multiple distinct foci, and Accommodative IOLs, which change in shape and power when the ciliary muscle contracts.
Traditionally with these technologies, the correction of presbyopia is commonly thought of in terms of the distinct distance for which functional vision is provided.
TECNIS Symfony IOL
Introducing TECNIS IOL, the first and only presbyopia-correcting extended range of vision IOL.
The TECNIS Extended Range of Vision IOL delivers a continuous, full range of high-quality vision with incidence of halos and glare comparable to a monofocal IOL.1, 2
TECNIS Extended Range of Vision IOL is available in both a Non-Toric version and a Toric version for patients with astigmatism.
Mechanism of Action, TECNIS IOL merges two complementary enabling technologies
- The proprietary diffractive echelette design feature extends the range of vision.1
- The proprietary achromatic technology corrects chromatic aberration for enhanced contrast sensitivity.2
Proprietary Diffractive Echelette Design Feature Extends The Range Of Vision
Proprietary diffractive echelette design feature introduces a novel pattern of light diffraction that elongates the focus of the eye resulting in an extended range of vision.1 As evidenced by the measured light pattern when projected through the TECNIS monofocal IOL, TECNIS multifocal IOL and the TECNIS Symfony extended range of vision IOL, there is one distinct focal point for distance with the TECNIS monofocal lens, two distinct foci for the TECNIS multifocal lens, and one elongated focal point for the TECNIS Symfony extended range of vision IOL.
Elongated Focus Leads to the Continuous Range of High-Quality Vision1
The novel pattern of light diffraction projected through the TECNIS Symfony IOL is shown below, along with the light patterns projected through the TECNIS monofocal and TECNIS multifocal IOLs for comparison.
The elongated focus of the TECNIS Symfony lens leads to:
- A continuous range of high-quality vision for far, intermediate, and near distances
- Halo and glare comparable to a monofocal (distinct single focus) IOL
- Multifocal IOLs work on the principle of simultaneous vision; one image is in focus while the out-of-focus image is suppressed; halos are caused by the out-of-focus image. Because the TECNIS Symfony IOL has one elongated focus it has the halo and glare profile comparable to a monofocal IOL.
Clinically Significant Increase In Range Of Vision
TECNIS IOL Showed:3
- 20/20 or better mean visual acuity from distance to 1.5 D of defocus
- 20/40 or better mean visual acuity from distance to 2.5 D of defocus
- 1.0 D increase in depth of focus throughout the defocus curve
Advances in IOLs, Available now in Canada/PVSC
TECNIS Eyhance (Distance and Intermediate Vision Monofocal IOL)
Monofocal IOLS have changed very little in recent years, in part because modern versions have already been providing excellent outcomes. The materials and edge designs were optimized in the 1990s, leading to lower rates of posterior capsular opacity (PCO). Aspheric optics were introduced, which improved optical performance, particularly with regard to contrast sensitivity. With modern lenses, we have long been able to achieve good centration with minimal tilt and stable axial IOL position after surgery.
However, a new monofocal IOL recently received the CE Mark and is commercially available throughout Europe and Canada. The monofocal lens (Tecnis Eyhance, Johnson & Johnson Vision) offers a slightly broader defocus curve, for high-quality distance and intermediate vision.
Intermediate vision in a prospective, multicenter, randomly selected subject- and evaluator-masked clinical trial in Europe, 67 subjects were implanted bilaterally with the new lens (study group) and 72 subjects with Tecnis onepiece (ZCB00) IOLs (control group). The study group achieved 20/20 best-corrected distance visual acuity (BCDVA) and significantly improved intermediate vision compared with the control group. The study group also had the same well-established low incidence of halo, glare, and starburst as Tecnis 1-Piece IOLs.
Patient-reported outcomes suggest that the Eyhance IOL allows patients to perform some activities, such as walking on uneven surfaces or engaging in hobbies, with greater ease compared to a standard aspheric monofocal. This IOL is not designed to give you reading vision, just to improve intermediate vision at 1 meter and up.
Eyhance Blended Vision (EBV)
Eyhance Blended Vision is similar to conventional monovision (MV). Both methods involve correcting the dominant eye for distance vision, while the non-dominant eye is corrected to be slightly nearsighted for near vision. Unlike monovision, EBV offers a greater range of sight (focal depth) in both the dominant eye and the non dominant eye. The advanced design of the distance Eyhance lens allows it to offer vision throughout far and intermediate ranges, reaching as close as 60cm away. This is complemented by the near eye’s ability to see from a meter away, to as close as 40cm. Together, these lenses overcome the weaknesses of monovision by covering the entire range of vision, from distance up to 40cm, without creating a Blur zone in the middle. Essentially, this new Blend Zone makes it easy for the brain to merge the images of both eyes thereby achieving true binocular vision. Overall, EBV helps adaptation and depth perception. The brain is typically good at blending images together seamlessly so that you don’t even notice which eye is being relied upon, but EBV shrinks the disparity between the two images to make that even easier. Many patients after surgery can’t even tell which eye is predominantly near or distance.
Unfortunately, all currently developed options for correcting near vision may encounter night vision issues. While driving at night, patients can sometimes experience halos around sources of light, but it tends to improve with time as the brain adapts by suppressing these halos as noise. In other corrective lenses, such as multi focal lenses, this is due to the rings on the lens and cannot be overcome with glasses. On the other hand, with EBV, halos are caused by the nearsighted eye’s focus on the intermediate and close range. To resolve this issue if it persists, we recommend using prescription night driving glasses to allow both eyes to work together and give the best possible vision at night.
TECNIS Synergy IOL (Continuous Vision Combo IOL)
Synergy is a “revolutionary” continuous-range-of-vision intraocular lens for patients with cataracts, which is now available in Europe, Australia, New Zealand and Canada. TECNIS Synergy™ IOL creates a new standard in presbyopia-correcting IOL technology, allowing patients to experience continuous high-contrast vision from far through near, even in low-light conditions. With TECNIS Synergy IOL, we have our most advanced IOL solution yet, which gives patients the clear, continuous range of vision they want, day and night.
The best of both worlds. Focus far through near, clarity day and night. The result – a revolutionary lens that:
- Gives broad range of continuous vision covering from distance to 33 cm
- Eliminates the visual gaps present in trifocal and other multifocal technology, offering patients the freedom to focus within the range
Continues to deliver superior performance in low-light conditions
- Violet-filtering technology demonstrates reduction in halo intensity for tasks like night driving, as demonstrated in clinical simulations.
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