INTRAOCULAR LENS IMPLANTS
Cataract surgery involves removal of the cloudy natural lens of the eye (“the cataract”). When the cloudy natural lens is removed, the eye is no longer in focus. For years, patients had to wear thick “cataract glasses” after cataract surgery in order to see anything more than a blurry shadow. When contact lenses were developed, they became an option to eliminate the use of these thick glasses. A huge advance was the development of lenses to go inside the eye, fitting in the space that remains when the cataract was removed. These lenses, called “intraocular lenses”, are made of plastic and come in different focal powers. The opthalmologist chooses the power of the lense implant based on measurements of the length and curvature of the patient’s eye. These measurements are used in a computer formula that calculates the power of the lense that should be needed to allow the eye to be in focus at distance without glasses. Most, although not all, patients can see enough to drive a car without glasses after cataract surgery and intraocular lens implantation. The level of vision that is achieved after cataract surgery depends on two factors : the health of the eye and the amount of remaining refractive error, such as nearsightedness, farsightedness, or astigmatism.
A healthy eye with no residual refractive error after surgery should be able to see approximately 20/20 after cataract surgery. However, if good vision is achieved at a distance without glasses after implant surgery, near vision (reading, computer, price tags, needlework, etc.) is usually not good without supplemental reading glasses. This is because the lens implant is unable to change focus (“accomodate”) in orde rto see clearly at different distances. This is the same issue that makes most people depend on reading glasses or bifocals after age 45 or so.
Most patients are accustomed to wearing glasses, and glasses after surgery can usually provide excellent vision for near and distance. On the other hand, many people find glasses inconvenient, and would love to see clearly without glasses. Some patients have chosen to have a lens implant set for distance vision in one eye, and an implant for near in the other eye. This technique, called “monovision”, has allowed many “over 45” patients to see both distance and near in their contact lenses and can also work nicely with lens implants. However, some patients do not adjust well to monovision.
An exciting recent development has been the introduction of lens implants designed to work for both near and distance vision. We offer two different (“premium”) implants have been approved by the FDA since 2004. They are:
- CRYSTALENS – The crystalens is hinged and moves very slightly forward inside the eye in order to change focus. The crystalens is called an accomodating implant.
- RESTOR – The ReSTOR lens focuses some of the light rays coming through the implant for near and some for distance. The ReSTOR is called a diffractive implant.
These premium implants are more expensive to manufacture and require additional work on the part of the surgeon to achieve optimal results. Therefore, there is an additional cost to the patient for the premium implant. Each implant has its own characteristics. Thousands of these new premium lenses have been implanted and although there are no controlled scientific studies comparing visual function wwith the different lenses, opthalmologists are beginning to have an idea of what patients can expect from each of the new lenses. However, each patient is different, and no promises or guarantees can be made about any individual’s result with any given lens implant.
In general, the crystalens provides good distance and intermediate vision, but some (probably 50%) of patients need to use glasses to do prolonged reading or to see fine print. The crystalens is not associated with more glare and halos than a standard lens implant.
The ReSTOR lens tends to provide good near vision. The ReSTOR has a near focal distance of about twelve inches, and is usually excellent for fine near work. However, intermediate range vision, such as computer monitors or price tags, may not be as good.
The ReSTOR is associated with significant glare and halos, particularly when driving at night. These tend to diminish with time, but generally do not disappear completely. Glasses will not make these halos go away. About one patient in one hundred is bothered so much by these unwanted images that they elect to have a second operation to replace their implant with a standard one.
Optimum performance with the premium implants is obtained only when the eye is healthy enough to achieve excellent vision. Therefore, most opthalmologists do not recommend the premium implants for patients with significant eye diseases, such as macular degeneration, diabetic retinopathy, or glaucoma. Also, unexpected complications at the time of cataract surgery, such as a tear in the capsule of the cataract, may prevent the surgeon from placing a premium implant in the proper position and a standard implant may be placed instead.
With any of the implants, the membrane behind the implant may become cloudy with time. A quick and painless laser procedure is sometimes required to open the cloudy membrane. Once the membrane is opened, it will not grow back. Insurance will usually cover this procedure.
Residual nearsightedness, farsightedness, and/or astigmatism after surgery (“refractive error”) can diminish the quality of both near and distance vision with any implant, standard or premium. Even though we use the most modern technology to predict the power of implant that a patient will need to achieve the desired refractive outcome, a small percentage (perhaps 20%) of patients will still end up with significant refractive error. Glasses, or occassionally contact lenses, can be worn after surgery to compensate for these issues. However, a patient who has invested a significant amount of money for a premium implant in an attempt to minimize their use of glasses is not likely to be satisfied if they need to wear glasses for all activities.
If significant refractive error remains after cataract surgery, additional procedures can be used to “fine-tune” the result. These procedures include Lasik, Lasek, astigmatic keratotomy, lens exchange, and “piggyback” lens implantation. We will provide these procedures at a discounted price (see attached). The patient must realize that additional surgical procedures are not free of risk, and may prefer to avoid the risk and expense of additional surgery and increase their uses of glasses instead.
Premium implants offer the possibility of significantly less dependance on glasses. For many patients, this is an exciting opportunity. For those patients who do not mind wearing glasses, a standard implant is included in the cost of cataract surgery, and should provide good vision with the use of glasses. The decision to have a premium implant needs to be based on an understanding of the benefits and risks of these implants, and we hope this information has been helpful. If you have any questions about your eyes or the available implants, please discuss them with your Cabarrus Eye Center surgeon.
Additional internet resources
ReSTOR – www.acrysofrestor.com
Crystalens – www.crystalens.com
Cataracts – www.nei.nih.gov/health/cataract/cataract_facts.asp