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IS REFRACTIVE SURGERY RIGHT FOR YOU?
Millions of people are regaining active lifestyles and preferred occupations with clear vision. Is LASIK right for you?
WHAT IS GLAUCOMA?
Glaucoma is a group of eye disorders that can lead to progressive loss of vision, often without any symptoms.
Index
Ocular Anatomy and Refractive Error
Preoperative Evaluation and Decision for Surgery
LASIK- Basic Information
LASIK- The Procedure in Detail
Custom LASIK- Wavefront Technology
LASEK
ICL- The Implantable Collamer Lens
Refractive Lensectomy
Conductive Keratoplasty
Introduction
It is estimated that more than 70 million Americans are nearsighted, and millions more are farsighted or have significant astigmatism. The majority of these individuals are reliant upon eyeglasses or contact lenses for clear vision. Despite great improvements in the visual quality achievable with modern lenses, many would prefer to leave their glasses and contacts behind in favor of good, unaided vision.
The first refractive surgical procedure, radial keratotomy (RK) was introduced to the United States from Russia in 1978. Since then, numerous other surgical options have become available for the correction of refractive errors, and surgical vision correction now ranks among the most commonly performed elective surgical procedures in the U.S. The following information is provided to educate you about the surgical choices available, and to help you decide if refractive surgery is right for you.
Ocular Anatomy and Refractive Error
The eye is a truly amazing organ. Just the size of a ping-pong ball, this complex little globe converts the light around us into vibrant images. While the anatomy of the eye is somewhat complex, its overall function is much like that of a camera. This section will explain how the normal eye works and how refractive errors such as nearsightedness and farsightedness develop.
As shown in the adjacent diagram, light passes through the clear cornea, the front window of the eye, which partly focuses the rays. The pupil, a round opening in the center of the colored iris, dilates and constricts to control the amount of light entering the eye, much like the diaphragm of a camera lens. Next, light passes through the lens of the eye, which sits just behind the iris. The lens further focuses the light, which continues on through the clear vitreous which fills the majority of the eye. Light finally arrives at the retina, a tissue paper thin membrane which lines the inside of the eyeball. The retina is the eye's film, sensing the light we see and converting it into signals which are then sent on to the brain via the optic nerve. The brain, like a computer, further processes information from the retina, creating the images we see.
In the normal eye, distant light rays are precisely focused by the cornea and lens onto the retina, leading to excellent visual acuity, generally 20/20 or better. (This numerical description of visual acuity means that the person being tested can see at 20 feet what a normal sighted person can see at 20 feet. The limit of normal human visual acuity has been determined by study of the eye.) If there is an imbalance between the power of the refractive structures of the eye (cornea and lens) and the eye's length, light will not be properly focused on the retina. Depending on the type of imbalance, either nearsightedness, known as myopia, or farsightedness, known as hyperopia, occurs. These refractive errors are measured in units known as diopters .
Nearsightedness (myopia) develops if the cornea/lens power is too strong, or the eye is too long. In this case, a person can see well at near, but distant objects are out of focus. Corrective lenses refocus the light onto the retina in order to improve distance visual acuity (see diagram at left). Refractive surgery either reshapes the cornea or uses an implanted lens to refocus light properly onto the retina to achieve good vision.
Farsightedness (hyperopia) occurs if the cornea/lens power is too weak, or if the eye is too short. This leads to poor near vision and better distance vision, though in some cases vision is not clear at any distance without correction (see diagram at right). Again, corrective lenses or refractive surgery can refocus light to achieve good acuity.
Astigmatism develops when the curvature of the cornea or lens is irregular, leading to different refractive powers depending upon the direction of the incoming light. This condition also leads to blurring of vision and can be corrected with lenses or surgery.
Presbyopia is the age-related loss of the ability to change focus from far to near. Most people notice its onset between 40 and 45 years of age. Before the onset of presbyopia, the normal human lens can change shape as muscles inside the eye adjust, allowing continually adaptive focusing of the eye. As presbyopia develops and progresses, the flexibility of the lens and muscles diminishes, and reading glasses or bifocals become necessary for near viewing. Presently, one FDA-approved procedure, conductive keratoplasty (CK) is available specifically for the treatment of presbyopia. This will be discussed later.
Is Refractive Surgery Right for You?
While most refractive errors can be corrected to some degree with either glasses or contact lenses, many find that this is not a satisfactory or convenient solution. Studies suggest that the majority opt for surgery because they desire more freedom from glasses or contacts. About 25% have become contact lens intolerant, and another 10% are motivated by sports interests or occupational/professional reasons. Below are some suggestions, restrictions, and guidelines to help you determine if you are a good surgical candidate and what to expect after surgery.
Requirements and Restrictions: Generally, the best candidates for LASIK and other refractive procedures are between 25 and 55 years of age, however those older or younger are not necessarily excluded. A great deal depends on the individual’s health, lifestyle, and degree of motivation with respect to decreasing dependency on glasses or contact lenses.
Limitations as to the degree of myopia, hyperopia, and astigmatism that can be corrected vary by procedure. Presently, LASIK has the highest tolerance of all existing procedures, and has been employed to correct as much as 14 diopters of myopia, about 6 diopters of hyperopia, and 6 diopters of astigmatism. These are upper limits of correction, and may not apply to any one individual. In any case, the patient should not have experienced more than a one diopter change in refractive error during the year prior to surgery. It is important to remember that while our ability to predict outcomes is quite good, nothing is infallible. The degree of correction achieved by any refractive procedure depends entirely upon the severity of the myopia, hyperopia, and/or astigmatism, with less accuracy as upper limits of correction are approached.
Preoperative Testing and Evaluation: Before arriving at a final decision to have surgical vision correction, a thorough evaluation of your candidacy for the proposed procedure by a qualified eye doctor is required. Because there are general health concerns that might preclude any type of procedure, this evaluation will include a full review of your overall medical condition. Additionally, refractive surgery is usually not recommended for people with moderate to advanced glaucoma, macular disease, or corneal diseases such as herpetic keratitis, keratoconus, severe dry eye, corneal dystrophies, or any other significant eye pathology.
If you wear soft contact lenses, they should not be worn for at least two weeks prior to your evaluation. Gas permeable or hard lenses should not be worn for at least one month prior. Contact lens wear distorts the cornea, and these periods of no contact use allow the cornea time to recover fully. Failure to do so could lead to inaccurate measurements and poor surgical results.
A full ocular examination will be performed after a basic screening determines possible procedures to correct your vision. This exam will include:
- Refraction: accurate measurement of the eyes’ refractive state to determine the amount of myopia, hyperopia, or astigmatism present.
- Keratometry: determination of the corneal curvature and power.
- Corneal pachymetry: ultrasound is used to measure the thickness of the corneas, important in determining the safety of certain procedures. Normal thickness is about 540 microns.
- Computerized corneal topography: a sophisticated device creates a computerized elevation map of the cornea, looking for any irregularities that might indicate problems such as keratoconus, which could lead to poor surgical outcomes.
- Tonometry: measurement of the intraocular pressure, looking for signs of glaucoma.
- Slit lamp/ophthalmoscopy: examination of the internal structures of the eye, looking for any other problems such as cataracts or retinal/macular disease.
Results/Expectations: As a result of all the preoperative testing, your surgeon will be able to determine three basic things:
- If you a good candidate for any type of surgical vision correction.
- Which procedure is best suited to your particular situation.
- What kind of visual result you can expect from the surgery.
This is the time to ask your surgeon questions and go into detail about your expectations regarding the surgery. If you are expecting too much in the way of uncorrected visual acuity given your degree and type of refractive error, you may ultimately be disappointed with the results. This may make you a poor candidate for a particular procedure. Results from LASIK and other procedures have generally been excellent for those patients with realistic expectations. Many achieve 20/20 vision almost immediately after surgery, while others achieve 20/40 or better vision without glasses or contacts- vision good enough for an unrestricted driver’s license in most states. Typically, those who do not reach 20/20 were told not to expect perfection and are therefore delighted with the results they do achieve. Much depends upon each patient’s individual condition and expectations.
It should be pointed out that there are always risks involved with any type of surgery and, although vision correction procedures are among the most successful and safe of all surgical procedures, this is true for refractive surgery as well. These risks are minimized by the precise and thorough preoperative tests conducted by our doctors and technicians using state-of-the-art instrumentation. As with any surgical procedure, you must understand all the risks prior to proceeding, and are required to sign a surgical consent form before undergoing the procedure. This consent should be read thoroughly and not signed until all your questions are satisfactorily answered. A detailed discussion about potential risks of each procedure is beyond the scope of this article and should be conducted with your surgeon.
Experience has shown that those who have taken the time and made the effort to become well informed regarding all aspects of refractive eye surgery and the available options make the best candidates and are more satisfied with the results. The various refractive surgical options available will be discussed in the sections that follow.
LASIK
This highly successful procedure combines the best qualities of two previously approved refractive surgical techniques: Automated Lamellar Keratoplasty (ALK) and Photorefractive Keratectomy (PRK). Although these two procedures have been virtually supplanted by the LASIK (Laser In-Situ Keratomileusis) procedure, we believe you will better understand LASIK if you know something about the procedures from which it was derived.
Photorefractive Keratectomy (PRK): The excimer lasers employed in all laser-based refractive surgery were first approved by the FDA for the PRK procedure in late 1995 after nearly ten years of extensive testing. As with all corneal refractive surgery aimed at correcting nearsightedness, the objective of PRK is flattening of the central cornea in order to focus light properly on the retina.
The first step in PRK is removal of the corneal epithelium, the thin, outermost layer of the cornea. This is usually achieved with the help of surgical instruments. The excimer laser, a computer-controlled device capable of very precisely removing thin layers of tissue, then ablates (vaporizes) corneal tissue in order to “sculpt” the corneal surface into the desired shape. The pattern of sculpting is determined by measurements from your preoperative evaluations, which are input into the laser’s computer. Under the skillful guidance of your surgeon, the computer directs the firing of the laser to achieve the specified pattern. Healing is delayed, with discomfort common during the first few postoperative days.
Automated Lamellar Keratoplasty (ALK): The basic procedure of ALK was developed by a Columbian physician in 1949, but was not widely accepted until refined over many years. It is capable of correcting very large degrees of myopia. The ALK procedure employs an instrument called a microkeratome to create corneal flaps, allowing the necessary reshaping of the cornea. Healing time is very rapid, usually within 24 hours, with rapid restoration of vision and little discomfort. The procedure is less accurate than laser-based surgery.
Laser In-Situ Keratomileusis (LASIK): This highly successful procedure combines the minimal postoperative discomfort and rapid visual recovery of ALK with the computer-controlled precision of PRK. LASIK is now the most commonly performed refractive surgical procedure in the world.
As with ALK, the initial step in LASIK is creation of a corneal flap using either a microkeratome, or more commonly the IntraLase laser (see details below). Once the flap is folded out of the way, the excimer laser is used to sculpt the cornea as determined by ocular measurements. The corneal flap is then gently repositioned by the surgeon, sealing down within minutes. Vision is often good within 24 hours with minimal discomfort. Complete healing takes about one month.
For more information about the LASIK procedure, read the following step-by-step explanation of the surgery.
The LASIK Procedure in Detail
Step One: Preoperative preparation and measurements: In our practice, LASIK is performed on an outpatient basis at the Arizona Eye Laser Center on Campbell Avenue. Although the procedure itself takes only a few minutes to complete, you should plan to spend a couple of hours at the center. Some of this time will be spent preparing you and your eyes for the procedure, while a few minutes will be required afterwards for postoperative instructions and departure preparation.
Before the procedure begins, a nurse or technician will talk to you about any immediate health problems that may affect your readiness for the surgery. At this point, additional eye measurements will be taken if you are undergoing wavefront LASIK (read about wavefront technology below). Anesthetic eye drops will be given to completely numb your eyes during the entire procedure.
Step Two: Creating the Flap: Currently, we create most LASIK flaps using the IntraLase® laser.This advanced technology “femtosecond laser” allows the formation of a corneal flap of any shape and size with tremendous precision, virtually eliminating the blade-related complications of a metal microkeratome. All cutting is done by laser, with no sharp instruments ever touching the eye. IntraLase LASIK has now been approved by the U.S. military for Air Force pilots, and by NASA for astronauts due to its precision and safety.
You will be comfortably positioned under the IntraLase device and a suction ring will be moved into place around your eye. Using a vacuum, this ring will hold your eye perfectly still while the laser creates the flap, a process that takes about 10-15 seconds. During this time you might feel a slight pressure, but no pain, and your vision will be diminished. Once the suction ring is released, you will notice a diffuse haze over your vision as the flap fully develops over the following few minutes. The procedure is then repeated on your second eye, if both are being treated.
In occasional cases, a microkeratome might still be used to create the flap. The overall process is similar, with placement of a suction ring. The microkeratome, which functions somewhat like a carpenter’s plane with a rapidly oscillating blade, passes over the cornea to cut the flap. This takes about 10 seconds, with no pain.
Click here to learn more about IntraLase technology.
Step Three: The Excimer Laser: Your eye is now ready for the final phase of LASIK- administration of the laser pulses to reshape the cornea. You will lie comfortably below the laser aperture and the area around your eyes will be prepared with a sterile cleanser. A plastic or paper drape will be placed around the eye, and a small eyelid separator will be placed to keep the eye open. Your surgeon will use an instrument to gently lift up and fold back the previously created corneal flap. You will not feel any discomfort. The surgeon will ask you to look towards a fuzzy, blinking red light above you. You do not need to worry about small eye movements, as the laser tracks the movement of your eye and adjusts its aim accordingly. It will stop firing completely if you move too far off track. As the surgeon activates the laser, you will hear a rapid “clicking” or “tacking” sound, and may smell an odor similar to hair burning. Again, you should feel no discomfort whatsoever. The total number of laser pulses required depends upon the amount of refractive error being corrected, but seldom last longer than one minute. When the laser is complete, your physician will irrigate away any debris with a sterile solution and then carefully reposition the flap. A contact lens may be placed on the eye to help the flap heal more quickly.
Step Four: Postoperative Measures: When the procedure is complete, antibiotic drops will be given and your surgeon will cover your eye with a clear plastic shield. For a short time after the surgery, you will not have much sensation due to continued numbness. However, later in the day you may experience some light sensitivity and a scratchy or dry sensation as though you have dust in your eye. This usually resolves within a few hours. You should plan to have someone drive you home from your procedure, as you will most likely be given medication to help relax prior to surgery.
You will return to our office the following day for a postoperative examination. The flap will be checked to assure that it is healing properly. If present, the contact lens will be removed at this time. Vision at this time is usually between 20/20 and 20/40, depending on the degree of refractive error corrected. Vision may continue to improve over the next few weeks before stabilizing fully. At this point you should be able to go about your business as usual… with one exception- no more glasses or contact lenses!
Custom LASIK: Wavefront Technology:
The latest major advance in the LASIK procedure came with the introduction of wavefront technology to the field of refractive surgery. The result is something called “custom LASIK,” a procedure that allows a surgeon to customize the surgery to each patient’s unique vision correction needs. Studies indicate that wavefront-guided LASIK produces visual outcomes superior to conventional LASIK.
To understand how custom LASIK works, we first need to know that there are actually two categories of visual irregularities: lower-order aberrations and higher-order aberrations. The differences are easiest to understand if we think of lower-order as being responsible for how much we see, while higher-order determines how well we see. Traditional LASIK is limited to correcting lower-order irregularities, commonly called refractive errors. These include myopia (nearsightedness), hyperopia (farsightedness), and astigmatism, and account for over 80% of optical errors. Higher-order aberrations are irregularities other than refractive errors which can cause problems such as glare, halos, and shadows. For example, while two different people may be able to read the same 20/20 line on the eye chart, one may see the letters more distinctly, with better contrast and clarity, due to fewer higher-order aberrations.
Wavefront technology works by measuring how light is distorted as it passes through the eye and is reflected back. The result is a color, three-dimensional corneal map that is distinct to each eye, much as a fingerprint is unique. The map is used to diagnose aberrations and determine the proper corrections for the eye. This information is programmed into the excimer laser and helps guide the treatment during the procedure. Because the measurements are more refined than those used in traditional LASIK, there is a greater chance for achieving 20/20 vision or better. Custom LASIK also may limit the chances of reduced contrast sensitivity and night vision problems, including glare and halos.
The Arizona Eye Laser Center currently uses the Alcon LADARVision® 4000 laser with CustomCornea wavefront technology. Click here for more information about LADARVision technology.
Laser Epithelial Keratomileusis (LASEK)
LASEK is a modification of PRK, meant to decrease postoperative discomfort and shorten healing time. This procedure is also referred to as surface ablation. Rather than totally removing the surface epithelium, as in PRK, the surgeon loosens the epithelium and moves it aside, creating a superficial epithelial flap. Excimer laser treatment is then performed, similar to PRK. Once complete, the epithelium is gently replaced and a contact lens is placed on the eye.
LASEK/PRK may have advantages for certain patients, particularly those with thinner corneas or relatively small refractive errors. Surface ablation may also be a better option for patients with mild dry eye, as LASEK is less likely than LASIK to exacerbate this condition. Your surgeon may discuss this with you as an alternative to LASIK.
Implantable Collamer Lens (ICL)
Also known as the implantable contact lens, the Visian ICL® is a thin, prescription lens which is inserted into the eye to correct a very wide range of refractive errors. It is capable of treating rather large degrees of myopia or hyperopia, and may be an option for patients who are outside the treatment range of LASIK. Patients with thin corneas or significant dry eye problems may also be more suited to the ICL than to LASIK. The ICL is a permanent implant, capable of remaining within the eye for a lifetime. It is removable and fully “reversible,” easily taken out of the eye if necessary, such as if a cataract develops later in life. It cannot be seen within the eye.
The ICL is implanted in a short surgical procedure, lasting approximately fifteen minutes. Drops are given to dilate the pupil. After being anesthetized, the eye and surrounding skin are cleansed with a sterile solution. A surgical drape is placed over the face, and an eyelid separator is gently placed to keep the eye open. Two small incisions are made at the edge of the cornea, and a thick liquid is instilled into the eye to protect the cornea, iris, and lens. The ICL, which is made of a very soft and pliable material, is gently folded and inserted through a corneal incision. The lens opens inside the eye and is carefully manipulated into its final location just behind the iris and in front of the lens. The thick liquid is then removed from the eye and the pupil is brought back to normal size with medication. The small corneal incisions heal without any sutures. Antibiotic drops are given and a patch or shield is placed over the eye. Visual recovery with the ICL is nearly immediate, with most patients seeing well within hours of the procedure.
Click the image below to visit the Staar Surgical Visian web site or the image below right to watch the procedure as performed live on the Today Show.
Refractive Lensectomy
Sometimes called clear lens extraction (CLE), this procedure is essentially the same as that used to remove cataracts, with implantation of an intraocular lens (IOL) within the eye. The only difference is that the lens being removed is clear, having not yet developed into a cataract. (A cataract is the natural lens of the eye which has become cloudy, usually due to aging).
Refractive lensectomy may be a good option for patients who are moderately to highly hyperopic (farsighted), or for those in whom other refractive procedures might not provide stable vision, such as patients over 55 years old. Additionally, it may be appropriate for those seeking good uncorrected vision at both distance and near via use of multifocal intraocular lenses.
For details regarding lensectomy, please read the library chapters about cataracts and intraocular lens implants.
Conductive Keratoplasty (CK)
Conductive keratoplasty is currently the only surgical procedure approved by the FDA for correction of presbyopia. Presbyopia is the age-related loss of the ability to change focus from far to near. Most people notice its onset between 40 and 45 years of age. Before the onset of presbyopia, the normal human lens can change shape as muscles inside the eye adjust, allowing continually adaptive focusing of the eye. As presbyopia develops and progresses, the flexibility of the lens and muscles diminishes, and reading glasses or bifocals become necessary for near viewing. CK may be an option if you have good distance vision without glasses or contact lenses, however experience difficulty with near tasks.
CK was initially approved for treatment of hyperopia (farsightedness) in 2002, and for presbyopia in 2004. It is generally considered a very safe, non-laser procedure. No cutting or removal of tissue is involved. CK uses a small probe, as thin as a human hair, to deliver radio frequency waves into the peripheral cornea. These radio waves create heat which gently shrinks small amounts of corneal collagen, producing steepening of the central cornea. The result is a nearer focal point for the treated eye.
CK creates a condition known as monovision. Monovision refers to the use of one eye for distance vision and the other for near vision. The eye treated with CK- usually the non-dominant eye- will become slightly nearsighted, and will lose some of its clarity at distance. In time, the brain normally leans to adapt and use the appropriate eye as necessary. It is strongly recommended, though, that monovision be attempted with contact lenses before the surgical option is pursued.
Conclusions
We hope the information provided here has offered some insight into the current options available in refractive surgery. Every year, more and more people are choosing to live independently of glasses and contact lenses, with excellent surgical outcomes. Is refractive surgery right for you? We invite you to contact us to arrange a complimentary, no-obligation screening visit. You will have the opportunity to discuss your interests and concerns, and to determine whether you might be a good surgical candidate.
Call us today at 520-293-6740, and dial 106 to reach our refractive surgical coordinator.