Accommodation refers to the ability of the crystalline lens (located behind the pupil) of the eye to change shape in order to bring into focus objects located at different distances from our face. For instance, we might need to focus on the moon (infinity), our computer (intermediate, or about 60 cm) or a book (near, or about 40 cm). Different objects located at varying distances require our crystalline lens to instantly adjust to see them clearly. This process is similar to focusing a camera lens on an object when taking a picture.
There is a natural, but inevitable loss in the focusing power of our crystalline lens as we age, called Presbyopia. The ability of the crystalline lens to instantly change shape in order to focus light rays on the retina for near vision tasks gradually declines throughout life. Around age 43, most people begin to notice they must hold reading material farther away than usual. To correct this problem, bifocals, reading glasses or monovision contact lenses are increasingly required so by age 50 there is generally total dependence on corrective lenses.
View video: Why we need reading glasses as we mature.
The crystalline lens of the eye which has become cloudy and no longer perfectly transparent to light is called a Cataract; this condition results in hazy vision. Once visual function is sufficiently compromised,cataract surgery may be recommended by your doctor. The cloudy crystalline lens of the eye is removed during cataract surgery and exchanged with an artificial intraocular lens implant (IOL). If you are considerably younger than 50, and require cataract surgery, keep in mind that any remaining accommodative amplitude is immediately lost and you will typically need bifocals. For instance, a 30 yr old may require cataract surgery because of a dense lens opacity compromising vision, but the downside is this relatively young lens still has the ability to fully accommodate. After cataract surgery with IOL, vision will be expected to significantly improve, but the eye will also immediately lose the accommodation the cloudy crystalline lens had provided so this young patient will need bifocals after surgery. Conversely, older patients who require cataract surgery are already accustomed to bifocals and will still require them after surgery with a conventional IOL.
Conventional intraocular lenses (IOL’s) have a fixed focus and are not designed to restore the eye’s natural ability to focus (accommodate) following cataract removal. Until recently, patients undergoing lens implant surgery had no other choice but a monofocal, or single focus IOL. Monofocal IOL’s implanted in both eyes generally provide excellent uncorrected vision if both IOL’s are powered for distance (infinity) and pre-existing astigmatism, if any, is corrected at the time of cataract surgery; however, patient’s typically remain dependent on spectacle correction for near and intermediate vision.
Conventional IOLs and “MONOVISION”
Single focus IOL’s can be electively targeted for distance focus in one eye and intermediate or near focus in the other eye. When both eyes are open, this optical condition, called “monovision” provides good simultaneous distance and intermediate (computer distance) or reading distance but the downside is some loss of binocularity or sterovision. Not all patients tolerate such an imbalance and may not accept “monovision”. Others may gradually adapt to this imbalance over time (several months). Still others only notice problems in low light or night illumination. Distance driving glasses may be all that is needed.
If you are approaching or are in the presbyopia age range (above age 40), you may already be familiar with this arrangement if you’ve worn contact lenses set up for monovision. If you have an interest in this option, you may ask your doctor to “tailor” the surgery (leave some residual near-sighted ability in your non-dominant eye) to allow some independence from reading glasses.
Presybyopia IOL’s are more recent innovations that are designed to significantly improve depth of focus. Use of these IOL’s during cataract extraction or refractive lensectomy may reduce or eliminate the need for corrective lenses for distance, intermediate and near visual tasks. Since both eyes are generally focused at a similar distance, stereopsis or depth perception is maximized. While Presbyopia IOL’s have definite advantages over conventional monofocal IOL’s it is important to realize that they do not yet simulate the full range of accommodation provided by the young human crystalline lens!
Unlike Conventional IOL’s, Presybopia IOL’s are NOT a covered benefit of your health insurance and instead are considered an “upgrade”. Additional out-of-pocket fees will apply if you elect this option.Payment plans are provided. Please contact us for more information.
There are currently three US FDA approved Presbyopia IOL designs,Crystalens ® (Eyeonics), Rezoom ® (AMO), and Restor® (Alcon) each using different optical principles to achieve better depth of focus. Each has advantages and disadvantages.
The following is a brief summary of the Crystalens ® and Rezoom ® and does not attempt to present a full discussion of the benefits and risks that may be associated with their use. Be sure to talk to your doctor who will determine if you are a suitable candidate and before making any decisions about vision improvement procedures, as this information is not intended to replace the advice of a healthcare professional.
|Crystalens ® view video: presbyopia and how crystalens® works|
|The first and only FDA approved accommodating intraocular lens|
|The only lens that uses the natural focusing ability of the eye|
|The only lens that provides a single focal point throughout a continuous range of vision from far to near|
|The crystalens® is intended for the visual correction of aphakia secondary to the removal of a cataractous lens in adult patients with and without presbyopia|
In Clinical Trials:
|•||98.4% of patients implanted with crystalens in both eyes could pass a driver’s test without glasses|
|•||100% could see intermediate (24″ to 30″) without glasses, the distance for most of life’s activities|
|•||90% could see well enough to read the newspaper without glasses|
|•||Some patients did require glasses for some tasks after implantation of the crystalens|
|•||Significantly more patients implanted with a crystalens (88.4%) could see better at all distances then patients implanted with a standard IOL (35.9%)|
The crystalens accommodating intraocular lens is engineered with a hinge designed to allow the optic, or part of the lens that you see through, to move back and forth as you constantly change focus on images around you.
|Your ciliary muscle contracts, causing the lens to gently move forward and to focus on images that are NEAR.||To go from NEAR to INTERMEDIATE vision, your ciliary muscle must slightly relax, allowing the lens to gently reshape.||When your ciliary muscle is totally relaxed, your lens is back and you are able to focus on images within you DISTANCE field of vision.|
In the late 1990s, Advanced Medical Optics (AMO) introduced its first multifocal IOL designed to provide multiple points of focus, thereby dramatically reducing the need for bifocals or trifocal glasses after surgery. Today, with its many optical design enhancements, AMO’s second-generation ReZoom™ Multifocal IOL provides patients with a full range of vision and greater independence from glasses or contact lenses than ever before. Clinical studies show that 92% of those receiving the ReZoom™ Lens technology “never”, or “only occasionally,” need to wear glasses.1
1. Package Insert. ReZoom™ Multifocal Acrylic Posterior Chamber Intraocular Lens. Advanced Medical Optics, Inc.
Rezoom ® Multifocal Lens Technology
Balanced View Optics™ Technology literally provides multiple focal points so you can see well at a variety of distances. The ReZoom™ Multifocal Lens has five uniquely proportioned visual zones designed to provide clear vision for different light and focal distances. Due to this design, about 20% of patients with this IOL experience visually significant halos and glare, usually at night. Most patients who experience these effects report they generally become less noticeable or bothersome over a period of several months to a year due to a natural process called neural adaptation. Rarely, it may occasionally become necessary to exchange this IOL with an alternative IOL should disabling glare persist and not spontaneously resolve.
The First Steps to Resuming Life
If you suffer from poor vision, or think you might have a cataract, you should make an appointment to have a complete eye examination. Once it is determined that you are a good candidate for a Presbyopia IOL, you will be given additional information about the possible risks, complications, and costs involved with the procedure. Be sure to have all of your questions answered before giving your consent to have surgery.
Learn more about cataract surgery.