New LASIK Eye Surgery Technology and Options
While the most popular and widely practiced vision correction procedure performed today is LASIK, laser eye surgeons have access to a wide variety of refractive procedures that may be employed, should your particular needs not fall into the realm of LASIK. The most exciting and potentially beneficial procedures will be based on a technology known as wavefront guided laser eye surgery or Custom LASIK, which is a method of completely customizing your refractive procedure.
Custom LASIK: Wavefront-LASIK Laser Eye Surgery
Many patients do not realize that the eye is an imperfect optical system. As light rays from distant objects pass through the individual optical components of the eye, they are subject to being distorted by the imperfections found in the cornea and the crystalline lens.The distortions that are created are referred to as “aberrations.” The vast majority–90% or more–of these aberrations create common refractive errors, such as nearsightedness, farsightedness and astigmatism, which can be treated by optical devices, like glasses and contact lenses, or by Laser Vision Correction, using the conventional methods of LASIK or PRK. The remaining 10% of optical aberrations create images which are altered by chromatic aberration, spherical aberration, diffraction, curvature of field, coma, trefoils and quadrafoils–collectively known as “higher order aberrations.” These higher order aberrations only occur in a visually significant manner in 10% to 15% of the general population. When they do occur, they are entirely unique to a particular patient–much like a fingerprint. For these patients, the use of a wavefront-guided laser technique to create a completely customized reshaping of the surface of the cornea may be the best treatment option.
To achieve a Custom LASIK, it will require measuring the higher order optical aberrations using a wavefront analysis system called an aberrometer and then digitally interfacing it with a laser, using high speed computerized control to direct the delivery of a very tiny beam of laser energy across the cornea.
The Aberrometer Wavefront Measurement System lets the surgeon see refractive aberrations in clear and accurate, rotating 3-D images. This is accomplished by the Aberrometer sending low-energy laser light into the eye. The light reflects off the retina and travels back through the lens and cornea as an outgoing wavefront.
This wavefront is captured by the Aberrometer, which then measures it to determine both higher and lower order aberrations of the entire optical system. The aberrations are then displayed on-screen in precise 3-D images.
To then create a customized corneal ablation from the aberrometer measurements we digitally interface that data with the Excimer Laser System. The Excimer Laser System incorporates the use of a tracking system which is a high-speed computerized eye tracking method that helps the LASIK surgeon enhance your treatment by providing precise registration of the laser beam to create a customized ablation surface.
Custom corneal ablation can be performed by your surgeon, whether you have LASIK or PRK, which we will discuss next.
Intacs Corneal Ring Segments
Approved in April 1999, the IntacsTM corneal ring segments offer patients with mild myopia and minimal astigmatism another option for correcting their nearsightedness. Currently, the rings are approved for correction of nearsightedness up to 3.00 diopters in patients twenty-one years or older who have no more than 1.00 diopter of astigmatism. This procedure does not correct astigmatism, and patients who have astigmatism–even less than 1.00 diopter–need to understand they will be astigmatic postoperatively.
The procedure involves inserting two small plastic “ring” segments in the peripheral cornea through small incisional channels. A temporary suture is then used to close the incision. The rings cause the central cornea to flatten. The advantage of IntacsTM is that the tiny ring segments may be removed if the patient wishes to reverse the correction.
In most patients in the clinical trials, when the rings were removed, the eyes went back to their preoperative state. In a few patients, they did not. Because of those few patients whose eyes did not return exactly to their preoperative condition, the FDA will not allow the use of the term “reversible,” but Intacsâ˘ are removable if desired.
Intacsâ˘ insertion is accomplished in a time frame slightly longer than LASIK, taking roughly fifteen minutes per eye under anesthetic drops. The recovery of clear vision seems to take slightly longer than LASIK and doesn’t seem to have quite the “wow” effect of rapid visual recovery. In addition, patients tend to experience more postoperative discomfort. The procedure is newer than LASIK or PRK, so it doesn’t yet have the track record that the other two procedures do.
The cost of Intacs is roughly equal to or more than LASIK in most centers. Removal of the rings, either for fine tuning the result or from dissatisfaction, is accomplished with a second surgery. The segments are removed, the eyes are allowed to heal, and an alternate procedure (such as LASIK or PRK, or a change in ring size) may be performed once the eyes have healed. The treatment range for Intacs is currently very limited, and they cannot treat astigmatism; hence, patients with astigmatism are not good candidates for Intacs.
Astigmatic Keratotomy (AK)
Astigmatic Keratotomy (AK) is similar to RK, but its purpose is to correct astigmatism. Usually, two incisions are made in the cornea in such a way as to make it more round (analogous to loosening the laces on a football). This procedure is often combined with radial keratotomy (RK) and has a similar long track record.
AK is still considered an excellent procedure for correcting pure astigmatism (patients without coexisting nearsightedness or farsightedness). AK can also be used to enhance the results of LASIK and PRK by correcting small residual amounts of astigmatism. However, most surgeons prefer to correct astigmatism with the excimer laser.
For patients with significant cataracts who are looking for an option for correcting their nearsightedness or farsightedness, cataract surgery presents the best option for achieving this goal. After removing the cataract with ultrasonic power, the surgeon can implant a lens that will reduce or eliminate nearsightedness and farsightedness. With the development of new toric intraocular implants, astigmatism can also be treated.
This procedure is not performed in younger patients without cataracts because the surgery involves entering the eye and, therefore, slightly increases the risk of more serious complications. The surgery also involves removing the natural crystalline lens, which in young people allows them to focus up close. LASIK surgery, which leaves the lens intact, is a better option for younger patients.
Automated Lamellar Keratoplasty (ALK)
Automated Lamellar Keratoplasty (ALK) is a refractive procedure that was done on high myopes prior to the invention of the excimer laser. It is similar to LASIK in that it uses a special instrument called a microkeratome to separate the surface layer of the cornea. This “flap” is temporarily folded back (similar to the first part of the LASIK procedure), and a thin disc of corneal tissue is removed with a second pass of the microkeratome. The procedure is much less precise than LASIK and was associated with a much higher complication rate. It is primarily used to correct large amounts of myopia.
Satisfactory results are not always obtained the first time though, and a high percentage of eyes need additional procedures to achieve the desired result. Sometimes an irregular corneal surface results from the procedure, causing some distortion of vision.
Automated lamellar keratoplasty is rarely performed today due to the advent of LASIK. LASIK has essentially replaced ALK because of the increased accuracy afforded by the excimer laser in making the second “cut.”
Radial Keratotomy (RK)
Until recently, Radial Keratotomy (RK) was the most commonly performed refractive procedure for nearsighted patients. With the aid of a high-powered microscope, the surgeon makes a series of radial microscopic incisions (usually between four and eight) on the surface of the cornea in order to reduce its curvature. This procedure is well suited for patients with low myopia and has been used for over twenty-five years. A form of RK called mini-RK is still used occasionally for very minute degrees of nearsightedness, such as those resulting from slight undercorrections in LASIK.
Although rarely performed as a primary procedure anymore because of the increased accuracy and stability of the excimer laser techniques, RK is still an effective vision correction technique and is used in those areas of the world that do not have access to the much more expensive laser technologies.
Bioptics is a combination procedure involving a phakic intraocular lens implant followed by LASIK. It is recommended for the most extreme levels of myopia and hyperopia when neither technique alone will entirely correct the refractive error. This combined technique can be used to correct over 30.00 diopters of myopia–nearly twice the maximum amount of myopia that can be safely corrected with LASIK.
Clear Lens Extraction (CLE)
Clear Lens Extraction (CLE) involves removing the internal lens of the eye, just like in a cataract operation. This is done with a special ultrasound instrument and may be done with eye-drop anesthesia (similar to LASIK). The procedure can be performed without the need for stitches. A flexible synthetic lens implant of the proper power is then placed inside the eye through an extremely small incision to correct the refractive error.
This procedure is more commonly performed for treating higher levels of farsightedness in patients over age forty. The optical results are excellent and the visual recovery period is brief. Clear lens extraction may also be used to correct higher levels of nearsightedness and may be fine tuned with LASIK if a small refractive error remains. Some surgeons have used this procedure to treat extremely nearsighted or farsighted patients who are not candidates for PRK or LASIK.
The major drawbacks of this procedure are the increased risk of postoperative retinal detachment, the increased risk of intraocular surgery, and that patients usually need reading glasses afterward. An intraocular lens called the ARRAY is a multifocal lens that can be implanted at the time of lens extraction. The ARRAY intraocular lens allows you to see both near and far after the operation. In order for it to work to its maximum potential, both eyes should be implanted with the lens. Because of its multifocal capacity, some patients experience a loss of contrast at night and also develop halos around lights. If these symptoms become problematic, the ARRAY lens can be removed and replaced.
Conductive Keratoplasty (CK)
Our 40’s present us with the inevitable need for bifocals or reading glasses. A recently FDA approved vision correction option, called Conductive Keratoplasty, or CK may be a solution for some. CK is a simple, non-laser technique that can be used to restore the ability to see close-up and even read small print.
Although you might have perfect distance vision, your ability to see close objects and the ease with which you can shift your focus between distant and close objects, begins to decrease at about age 40–and usually continues to slowly, but progressively, worsen with age. Currently, more than 70 million Americans who are over the age of 40 are farsighted or have difficulty reading small print at close distances. For many of these people, CK may offer an alternative to bifocals or reading glasses.
CK uses a precisely controlled emission of radio frequency (RF) energy to reshape the cornea. CK does not use a laser or require cutting or removal of any corneal tissue. Since it is considered minimally invasive, the CK procedure avoids the risk of most surgical procedures.
In CK, a few numbing drops are placed in your eye so that you are comfortable. A circular treatment pattern is placed on the cornea, using easily rinsed ink. The surgeon then uses a tiny probe–thinner than a strand of human hair–to apply the RF energy to the cornea in the circular pattern, in order to shrink small areas of corneal tissue. This circular shrinkage pattern causes a fine band of tissue to contract, similar to tightening the belt around your waist. This results in the cornea becoming steeper and increasing its focusing power.
CK is quick, usually taking less than three minutes per eye. CK is performed in the comfort and convenience of the surgeon’s office. The majority of CK patients are able to return to work and other normal daily activities the day after treatment. Many experience improvement in their vision almost immediately. The full effect of CK usually takes a few weeks as your eyes adjust to the treatment.
Laser Thermal Keratoplasty (LTK)
For low amounts of farsightedness, a technique called Laser Thermal Keratoplasty (LTK) is a possible method of thermally changing the shape of the cornea. A special holmium laser is used to deliver laser energy to the peripheral cornea to slightly tighten the fibers and thereby steepen its curvature. The technique only seems to work for low amounts of farsightedness.
The Sunrise Hyperion LTK System received FDA approval for the treatment of hyperopia (0.75 to 2.50 diopters) in January 2000. The procedure is noncontact, takes less than three seconds per eye, and is performed with the patient seated. Many doctors see the benefits of the LTK system for treating not only low degrees of hyperopia, but also occasional overcorrections from LASIK procedures. Although not a cure for presbyopia, some physicians are using LTK to create monovision in patients, thus treating presbyopic symptoms by reducing or eliminating the need for reading glasses.
Phakic Intraocular Lens (PIOL) Implants
Implantable contact lens technology has arisen out of the incredible advances in modern cataract surgery. Current technology allows ophthalmologists to insert flexible intraocular lenses (used to replace the natural lens after cataract surgery) through extremely small incisions. The lenses are flexible enough to allow folding and insertion through a small incision opening.
Once in the eye, the lens expands to its full size, allowing the eye to remain relatively untraumatized, thus reducing astigmatism and recovery time. This same “small incision” lens technology allows the surgeon to insert an even thinner, foldable lens in front of the natural lens to correct nearsightedness or farsightedness.
A Phakic Intraocular Lens (PIOL) is a lens implanted inside the eye for the correction of either extreme nearsightedness or extreme farsightedness. In effect, the lens becomes an internal contact lens rather than a contact lens on the surface of the eye. It is usually recommended for patients whose visual correction is outside the range that can safely be treated with LASIK.
Because of the slightly increased risk of more serious complications, the PIOL is reserved for high amounts of nearsightedness or farsightedness–above the current limits of LASIK. In places where this technology is available, surgeons are implanting the PIOL in patients with myopia greater that 12.00 to 15.00 diopters and hyperopia greater than 4.00 to 6.00 diopters.
Despite the excellent outcomes in most cases, complications associated with the implants are currently the biggest concern. Specifically, in the early studies a small percentage of patients developed cataracts shortly after implantation of the lens. There is also a small risk of endophthalmitis (infection within the eye) because the surgical incision actually enters the eye. This rare complication could lead to complete loss of vision. Endothelial cell loss with some lens designs is also a concern and is being studied rigorously.
Some ophthalmologists in the United States are currently performing this procedure as part of an FDA clinical trial. The procedure holds a lot of promise for extremely nearsighted or farsighted individuals. Ophthalmologists are anxious to see how the implantable lenses fare in current studies using newer lens designs and implantation techniques.
These lenses are currently being used in Europe and South America with very high success rates. The results will be presented to the Food and Drug Administration with the hope that the FDA will authorize other eye surgeons to use this exciting new technology.
Surgery for Presbyopia
One of the more exciting areas of ophthalmology is the surgical treatment of presbyopia, the stiffening of our natural lens that decreases near vision as we age. Several devices and surgeries have been tried, all of which direct their effect at enlarging the circumference of the front of the eye and tightening the fibers that control the focus of the lens.
One of the principle theories of presbyopia suggests that these fibers stretch and become less effective as we age. By enlarging the circumference of the eye, the fibers should once again become tight and thus effective at focusing the lens.
Anterior Ciliary Sclerotomy (ACS)
Anterior Ciliary Sclerotomy (ACS) is a surgical procedure for relieving presbyopia. It involves the creation of several small incisions in the sclera (coating of the eye) directly over the muscle that controls the eye’s natural lens. The purpose of this procedure is to expand the circumference around the equator of the eye.
Scleral Expansion Bands (SEB)
Scleral Expansion Bands (SEB) is another procedure for relieving presbyopia. It consists of a number of thin silicon bands implanted in the sclera to stretch or expand the equator of the eye in order to restore accommodation (the ability to read without corrective lenses after age forty-two).
The theory behind both procedures is that expansion of the eye will allow increased room for the eye’s natural crystalline lens to move normally, enabling the eye to see near objects again. These procedures are still being investigated in the United States.
To date, there is much controversy about both the theory and the effectiveness of these types of surgery. Until scientific studies show more consistent results, monovision and reading glasses or bifocals are still the best options for treating presbyopia.