Cataract Removal and Lens Implants
The human lens is normally clear and transparent to light rays. However, with aging and less commonly in certain disease conditions such as diabetes, the lens may become partly or completely cloudy. This condition is called cataract, and it is such a common problem that there are more than one million operations for cataract removal in the United States each year. Fortunately, when the most modern methods of microsurgery are used, this is the most highly successful of all operations.
Patients with cataracts frequently wonder whether they need surgery. Surgery is usually performed when the patient is no longer satisfied with his/her vision. The cause for the dissatisfaction can be blurred vision, difficulty reading, problems with glare or seeing street signs, poor night vision, difficulty seeing traffic signals or judging distances when driving, etc. Also, the statement that cataracts must be “ripe” in order to be removed is incorrect. As long as the vision problem is found to be caused by a cataract, removal of the cataract can be performed.
During cataract surgery, the entire lens, with the exception of the lens capsule, must be removed. This is true whether or not the entire lens has become cloudy, since any remaining lens would become cloudy immediately. Removal of the cloudy lens creates the need for lens replacements. If a cataract is removed and no replacement lens is used, vision is extremely blurred. In fact, the blurriness is similar to that which occurs when we open our eyes while swimming underwater. Lens replacement can be accomplished in any of the following three ways: glasses, a contact lens, or an intraocular lens implant. Let’s consider each of these lens replacement methods in more detail.
A strong eyeglass can be used to substitute for the normal human lens after cataract surgery. However, these glasses are very thick and heavy, and they do not produce normal vision. With these glasses, objects are magnified approximately 33% and side vision is greatly reduced. Because of these problems, cataract glasses are not the best method of lens replacement. As an alternative, a contact lens can be worn following cataract surgery. This solves the problem of wearing thick glasses and does not cause magnification of objects or loss of peripheral vision, but the difficulties of contact lens wear remain. Contact lenses can be difficult to insert and remove, and vision is often variable. In addition, cataract lenses worn overnight can sometimes produce serious eye infections. Because of the difficulties with the first two types of lens replacements, almost all cataract operations are now performed with simultaneous lens implant. During this operation, the cataract is removed and an artificial lens is placed within the eye.
The great benefit of an artificial lens implant is that it solves all of the above problems associated with thick cataract glasses or contact lenses. This does not mean that patients never wear glasses following the operation, however. Normal types of eyeglasses are often worn in order to correct such conditions as astigmatism, or to improve vision for reading or driving. The human lens loses its ability to focus or change shape as we grow older. An artificial lens implant has no ability to change shape whatsoever, and therefore most implants provide clear vision only at a distance. Multifocal lens implants do exist, and can be used for those patients who wish to avoid glasses as much as possible. However, these lenses can cause patients to see haloes around lights. If a lens implant is placed within the eye so that distance vision is very clear, then near vision is blurred and spectacles must be worn for reading, and vice versa. If an implant is used which provides clear vision for intermediate distance of about three to six feet, then moderately good vision is present for distance and near. In order to obtain the clearest possible vision, these patients wear a relatively weak bifocal eyeglass. However, much of the time they are able to function without glasses due to the “all purpose” type of vision which they have when the best vision is at an intermediate distance.
Lens implants are made of either a hard plastic or a soft foldable material. Both of these types of lenses provide excellent vision, and differ mainly in the incision size required for insertion into the eye at the time of cataract surgery. The rigid plastic lens implants require an incision of slightly less than one-quarter of an inch, and the foldable soft implants require an incision of one-twelfth of an inch. The decision as to which implant is the best for an individual patient is determined by rather complex factors such as strength of the implant required and the amount of astigmatism present. At The Mackool Eye Institute and Laser Center, we often use a special implant to reduce or eliminate astigmatism at the same time that cataract and implants surgery are performed. This can result in better vision without glasses following surgery.
A lens implant and a dime.
After surgery, vision without glasses is often better than it was with glasses before surgery. And of course, when glasses are worn after cataract surgery, vision is almost always better than the vision before cataract surgery. In fact, more than 99% of the tens of thousands of cataract operations which Dr. Mackool has performed at the Institute and Laser Center have successfully restored all of the vision which had been lost due to cataract.
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The Methods of Cataract Removal
There are two basic methods of cataract removal: the large incision and the small incision methods. With the large incision method, an opening of approximately one-half inch is made at the top of the eye near the junction of the cornea and sclera. The entire cataract is then removed in one piece, and the lens implant is inserted. Remember that lens implants do not require a large incision for insertion; they can be inserted through an incision as small as one-eighth of an inch. As many as ten stitches may be required to close the incision. While healing and recovery of vision can be delayed, and removal of the stitches is often necessary, the final results are usually good.
Large incision cataract method with many stitches.
The second method of cataract removal takes advantage of the small size of lens implants. It allows removal of the cataract through an equally small opening (one-eighth inch) in the eye as that which is required for lens implant insertion. This method is called a phacoemulsification, and it allows the cataract to be removed through a tiny ultrasonic needle. The needle vibrates approximately forty thousand times per second, and this vibration acts to break up the cataract as it enters into the hollow needle and is removed from the eye.
Small incision cataract method (phacoemulsification) often requires no stitches.
It is extremely important that the eye remain inflated during this method of cataract removal. In order to accomplish this, the cataract must be replaced with fluid as it is removed. In 1978, Dr. Mackool conceived the idea of a computerized instrument which would more precisely control the rate of cataract removal, and balance it with the rate of replacement fluid entering the eye. The replacement fluid enters the eye through a second hollow needle which surrounds the vibrating needle. The first computerized instrument to control this process, and to thereby allow the pressure within the eye to remain normal during the operation, was the Mackool/Heslin Ocusystem. In 1993, Dr. Mackool patented a process which changed the design of the hollow needles in such a way that, after they were inserted into the eye, there was absolutely no leakage of fluid from the eye (between the outside of the needle and the tissues of the eye around the needle). This has proven to be a critical step which permitted even finer control of the pressure within the eye and greatly reduces the amount of fluid which passes through the eye during cataract removal. Because of its ability to “seal” the incision, the first model of this instrument was called the MicroSeal System. The most recent model, the Mackool System, recently received FDA approval and is now being used by surgeons throughout the world. With this type of instrumentation, the vast majority of my patients are able to have their cataracts removed in a brief and painless operation, and over 99% require no stitches. Healing is extremely rapid, and patients are able to return to normal activity immediately. Injections, and even bandages, are no longer necessary for more than 99% of patients. Vision improves quickly, and most patients have improved vision within 10 minutes after the operation!
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