Basik Lasik: Tips on Lasik Eye Surgery
Produced in cooperation with the American Academy of Ophthalmology.
If you're tired of wearing glasses or contact lenses, you may be considering Lasik eye surgery — one of the newest procedures to correct vision problems. Before you sign up for the surgery, get a clear picture of what you can expect.
The Facts
•Lasik is surgery to a very delicate part of the eye.
•Hundreds of thousands of people have had Lasik, most very successfully.
•As with any surgery, there are risks and possible complications.
•Lasik may not give you perfect vision. The American Academy of Ophthalmology (AAO) reports that seven out of 10 patients achieve 20/20 vision, but 20/20 does not always mean perfect vision.
•If you have Lasik to correct your distance vision, you'll still need reading glasses around age 45.
•Lasik surgery is too new to know if there are any long-term ill effects beyond five years after surgery.
•Lasik surgery cannot be reversed.
•Most insurance does not cover the surgery.
•You may need additional surgery — called "enhancements" — to get the best possible vision after Lasik.
Understanding Your Eyes
To see clearly, the cornea and the lens must bend — or refract — light rays so they focus on the retina — a layer of light-sensing cells that line the back of the eye. The retina converts the light rays into impulses that are sent to the brain, where they are recognized as images. If the light rays don't focus on the retina, the image you see is blurry. This is called a refractive error. Glasses, contacts and refractive surgery attempt to reduce these errors by making light rays focus on the retina.
Refractive errors are caused by an imperfectly shaped eyeball, cornea or lens, and are of three basic types:
•myopia — nearsightedness; only nearby objects are clear.
•hyperopia — farsightedness; only objects far away are clear.
•astigmatism — images are blurred at a distance and near.
There's also presbyopia — "aging eye." The condition usually occurs between ages 40 and 50, and can be corrected with bifocals or reading glasses.
Are You a Good Candidate for Lasik?
Lasik is not for everyone.
•You should be at least 18 years old (21 for some lasers), since the vision of people younger than 18 usually continues to change.
•You should not be pregnant or nursing as these conditions might change the measured refraction of the eye.
•You should not be taking certain prescription drugs, such as Accutane or oral prednisone.
•Your eyes must be healthy and your prescription stable. If you're myopic, you should postpone Lasik until your refraction has stabilized, as myopia may continue to increase in some patients until their mid- to late 20s.
•You should be in good general health. Lasik may not be recommended for patients with diabetes, rheumatoid arthritis, lupus, glaucoma, herpes infections of the eye, or cataracts. You should discuss this with your surgeon.
•Weigh the risks and rewards. If you're happy wearing contacts or glasses, you may want to forego the surgery.
•Understand your expectations from the surgery. Are they realistic?
•Ask your doctor if you're a candidate for monovision — correcting one eye for distance vision and the other eye for near vision. Lasik cannot correct presbyopia so that one eye can see at both distance and near. However, Lasik can be used to correct one eye for distance and the other for near. If you can adjust to this correction, it may eliminate or reduce your need for reading glasses. In some instances, surgery on only one eye is required. If your doctor thinks you're a candidate, ask about the pros and cons.
Finding a Surgeon
Only ophthalmologists (Eye MDs) are permitted to perform Lasik. Ask your Eye MD or optometrist for a referral to an Eye MD who performs Lasik. The American Academy of Ophthalmology website (www.eyenet.org) feature "Find an Eye MD" can provide you with a list of their members who perform Lasik. Ninety-five percent of all ophthalmologists (Eye MDs) are Academy members. Also, the International Society of Refractive Surgery website (www.LocateAnEyeDoc.com) will provide you with names of refractive surgeons.
Ask your surgeon the following questions:
1.How long have you been doing Lasik surgery?
2.How much experience do you have with the Lasik procedure?
3.How do you define success? What's your success rate? What is the chance for me (with my correction) to achieve 20/20? How many of your patients have achieved 20/20 or 20/40 vision? How many patients return for enhancements? In general 5-15% return.
4.What laser will you be using for my surgery? Make sure your surgeon is using a laser approved by the U.S. Food and Drug Administration (FDA). As of this publication's printing, the FDA has approved five lasers for Lasik; they are manufactured by VISX, Summit, Bausch and Lomb, Nidek and ATC. Contact the FDA for updates.
5.What's involved in after-surgery care?
6.Who will handle after-surgery care? Who will be responsible?
7.What about risks and possible complications?
Risks and Possible Complications
Before the surgery, your surgeon should explain to you the risks and possible complications, and potential side effects, including the pros and cons of having one or both eyes done on the same day. This is the "informed consent" process. Some risks and possible complications include:
•Over- or under-correction. These problems can often be improved with glasses, contact lenses and enhancements.
•Corneal scarring, irregular astigmatism (permanent warping of the cornea), and an inability to wear contact lenses.
•Corneal infection.
•"Loss of best corrected visual acuity" — that is, you would not be able to see as well after surgery, even with glasses or contacts, as you did with glasses or contacts before surgery.
•A decrease in contrast sensitivity, "crispness," or sharpness. That means that even though you may have 20/20 vision, objects may appear fuzzy or grayish.
•Problems with night driving that may require glasses.
•Flap problems, including: irregular flaps, incomplete flaps, flaps cut off entirely, and ingrowth of cells under the flap.
The following side effects are possible, but usually disappear over time. In rare situations, they may be permanent.
•Discomfort or pain
•Hazy or blurry vision
•Scratchiness
•Dryness
•Glare
•Haloes or starbursts around lights
•Light sensitivity
•Small pink or red patches on the white of the eye
Surgery: What to Expect Before, During and After
Before: You'll need a complete eye examination by your refractive surgeon. A preliminary eye exam may be performed by a referring doctor (Eye MD or optometrist). Take your eye prescription records with you to the exams. Your doctor should:
•Dilate your pupils to fine-tune your prescription.
•Examine your eyes to make sure they're healthy. This includes a glaucoma test and a retina exam.
•Take the following measurements:
oThe curvature of your cornea and your pupils. You may be rejected if your pupils are too large.
oThe topography of your eyes to make sure you don't have an irregular astigmatism or a cone-shaped cornea — a condition called Keratoconus.
oThe pachymetry — or thickness — of your cornea. You need to have enough tissue left after your corneas have been cut and reshaped.
•Ask you to sign an informed consent form after a thorough discussion of the risks, benefits, alternative options and possible complications. Review the form carefully. Don't sign until you understand everything in the form.
•If your doctor doesn't think Lasik is right for you, you might consider getting a second opinion; however, if the opinion is the same, believe it.
If you qualify for surgery, your doctor may tell you to stop wearing your contact lenses for a while before the surgery is scheduled because contacts can temporarily change the shape of the cornea. Your cornea should be in its natural shape the day of surgery. Your doctor also may tell you to stop wearing makeup, lotions or perfume for a few days before surgery. These products can interfere with the laser treatment or increase the risk of infection after surgery.
During: Lasik is an outpatient surgical procedure. The only anesthetic is an eye drop that numbs the surface of the eye. The surgery takes 10 to15 minutes for each eye. Sometimes, both eyes are done during the same procedure; but sometimes, surgeons wait to see the result of the first eye before doing the second eye.
The Surgical Procedure: A special device cuts a hinged flap of thin corneal tissue off the outer layer of the eyeball (cornea) and the flap is lifted out of the way. The laser reshapes the underlying corneal tissue, and the surgeon replaces the flap, which quickly adheres to the eyeball. There are no stitches. A shield — either clear plastic or perforated metal — is placed over the eye to protect the flap.
After: Healing is relatively fast, but you may want to take a few days off after the surgery. Be aware that:
•You may experience a mild burning or sensation for a few hours after surgery. Do not rub your eye(s). Your doctor can prescribe a painkiller, if necessary, to ease the discomfort.
•Your vision probably will be blurry the day of surgery, but it will improve considerably by the next day when you return for a follow-up exam.
•If you experience aggravating or unusual side effects, report them to your doctor immediately.
•Do not drive until your vision has improved enough to safely do so.
•Avoid swimming, hot tubs and whirlpools for two weeks after surgery.
Alternatives to Lasik
You may want to discuss some surgical alternatives to Lasik with your eye doctor:
•Photorefractive keratectomy (PRK) is a laser procedure used to reduce myopia, hyperopia and astigmatism without creating a corneal flap.
•Astigmatic keratotomy (AK) is an incisional procedure to reduce astigmatism.
•Intrastromal corneal rings are clear, thin, polymer inlays placed on the eye to correct low myopia only.
Thursday, September 18, 2008
Glaucoma Surgery
The surgical management of glaucoma is offered to patients if drug therapies have not been satisfactory or are inappropriate (e.g., because of the desire to avoid drugs during pregnancy). There are two types of surgical treatment: those using a laser and those using surgical techniques.
During laser treatment for open-angle glaucoma, laser light is aimed at the eye’s trabecular meshwork (the eye’s drainage system). The laser application results in a biological and mechanical reaction in the trabecular meshwork to open the previously blocked meshwork and increases the flow of aqueous fluid from the eye.
The most common conventional (incision) surgical technique is called filtering microsurgery, which involves making a hole through which the excess fluid drains and lowers pressure in the eye. Surgery is used if medication and laser procedures have not been successful or if there is a medical emergency for which pressure must be relieved immediately.
Laser Surgery
Laser surgeries lower intraocular pressure by enhancing the drainage of aqueous fluid or slowing its production. The kind of laser surgery used depends on the type of glaucoma being treated. The length of time the pressure remains lowered depends on the type of laser surgery, the type of glaucoma, and the patient’s individual characteristics.
In some cases, laser surgery may have to be repeated to control internal eye pressure more effectively. Typically, medications will still be needed to maintain fluid pressure within the eye, although a lower dose than previously used may be sufficient. If the laser therapy does not lower the pressure in the eye satisfactorily or the effects wear off, the surgeon may recommend conventional surgery.
What to expect: Laser surgeries are preformed in a doctor’s office in a facility called an ambulatory surgical center or in a hospital. Although some patients may experience a slight stinging sensation, the procedures are usually painless. In some instances, local anesthetic agents are used, in which case there is little if any discomfort.
When the procedure is over, patients may experience blurred vision and some irritation. Normal activities, such as driving and work, may be resumed the next day.
Risks: As with all surgery, there are risks. Risks of laser glaucoma procedures may include a short-term increase in intraocular pressure or an excessive drop in pressure. Both complications are rare and controlled with glaucoma medications. There is a small risk for cataract formation after some types of surgery.
Benefits: Failure to control glaucoma can result in destruction of the optic nerve and permanent blindness of the affected eye. Reducing or preventing raised intraocular pressure by laser therapy is effective in reducing the risk of blindness from glaucoma.
Laser Treatments for Primary Open-Angle Glaucoma
* Selective laser trabeculoplasty (SLT) reduces intraocular pressure by enhancing drainage of excess aqueous fluid. The laser increases drainage by selectively treating certain cell tissue of the trabecular meshwork. The meshwork is at the entrance of the drainage canals. SLT treatments can occasionally be repeated if necessary.
* Argon laser trabeculoplasty (ALT) reduces intraocular pressure by opening the drainage canals of the eye. In many cases, drugs will continue to be needed to maintain safe internal eye pressure after this procedure.
Laser Treatments for Narrow-Angle Glaucoma
* Laser peripheral iridotomy (LPI) reduces excessive intraocular pressure by making a small hole in the iris, the colored part of the eye. Narrow-angle glaucoma occurs when the angle between the iris and cornea, the clear front part of the eye, is too small. The hole allows the iris to move back from the cornea, opening the angle and enhancing aqueous flow.
* Laser cyclophotocoagulation is used to reduce eye pressure by treating the ciliary body, which produces aqueous fluid. The procedure is most commonly used for patients with extensive and end stage glaucoma damage that are not responding to other glaucoma surgeries.
Conventional or Incision Surgery
As noted above, conventional surgery or filtering microsurgery is used when management of glaucoma through medication and laser surgery has failed or is less desirable. Trabeculectomy is most commonly used to prevent or curtail damage to the optic nerve by reducing intraocular pressure. In this procedure, a small incision is made in the sclera of the eye (see Diagram 2) and a flap of tissue is left to cover the incision, allowing slow release of fluid from the inside the eye to its outer layers. The procedure results in the formation of a small blister-like bump called a “bleb.” The bleb is covered by the eyelid and is usually not visible. The excess fluid is carried away as it is absorbed into the bloodstream.
A new modification of trabeculectomy, is non-penetrating deep sclerectomy or viscocanalostomy, where a full-thickness hole in the eye is avoided. Instead, a very deep dissection is performed in the sclera and trabecular meshwork. Intraocular pressure is lowered as fluid oozes through a permeable thin layer of tissue that is created by the viscocanalostomy. A bleb may be formed, but it is usually smaller than one that would be formed following trabeculectomy.
In case of complicated glaucoma or patients who have had multiple surgeries, the use of a tube-shunt or seton is required. These devices, which include the Ahmed Valve, Baervedlt device, or Molteno device, have a plastic tube that is placed in the eye, which drains to an external reservoir placed outside the eye.
What to expect: Microsurgical procedures are performed in an ambulatory surgical center or on an outpatient basis at a hospital. Patients are usually given limited intravenous sedation but may be given general anesthesia. Medication may also be administered around the eye to prevent its movement. Typically, patients are relaxed and experience little if any discomfort.
Risks and benefits: The risks of incision surgery are small. Nevertheless, as with any incision, there is the risk of bleeding and infection. The eye may be red or inflamed, with discomfort and pain. In some instances, the procedure may not reduce eye pressure as intended. Loss of too much pressure can result in a loss of vision. As with laser surgeries, there are occasional instances in which the pressure is too high or too low. When this occurs, medications or additional surgeries may be needed to control the condition. In some instances, cataracts may develop. In very rare circumstances, an eye can be removed as a result of surgery. As with all procedures or medications, the risks need to be balanced with the benefits of saving vision in the affected eye. Failure to control glaucoma can result in destruction of the optic nerve and permanent blindness in the affected eye.
Success rates for glaucoma filtering surgery are about 70% to 90% for at least 1 year. In some instances, the surgically created drainage channel may “heal” or close, in which case high intraocular pressure can recur. The healing or closure of the drainage opening is a natural process that is more likely to develop in younger people. To prevent or retard closure, drugs such as mitomycin-C and 5-fluorouracil may be administered. If necessary, the surgery can be repeated in the same eye.
During laser treatment for open-angle glaucoma, laser light is aimed at the eye’s trabecular meshwork (the eye’s drainage system). The laser application results in a biological and mechanical reaction in the trabecular meshwork to open the previously blocked meshwork and increases the flow of aqueous fluid from the eye.
The most common conventional (incision) surgical technique is called filtering microsurgery, which involves making a hole through which the excess fluid drains and lowers pressure in the eye. Surgery is used if medication and laser procedures have not been successful or if there is a medical emergency for which pressure must be relieved immediately.
Laser Surgery
Laser surgeries lower intraocular pressure by enhancing the drainage of aqueous fluid or slowing its production. The kind of laser surgery used depends on the type of glaucoma being treated. The length of time the pressure remains lowered depends on the type of laser surgery, the type of glaucoma, and the patient’s individual characteristics.
In some cases, laser surgery may have to be repeated to control internal eye pressure more effectively. Typically, medications will still be needed to maintain fluid pressure within the eye, although a lower dose than previously used may be sufficient. If the laser therapy does not lower the pressure in the eye satisfactorily or the effects wear off, the surgeon may recommend conventional surgery.
What to expect: Laser surgeries are preformed in a doctor’s office in a facility called an ambulatory surgical center or in a hospital. Although some patients may experience a slight stinging sensation, the procedures are usually painless. In some instances, local anesthetic agents are used, in which case there is little if any discomfort.
When the procedure is over, patients may experience blurred vision and some irritation. Normal activities, such as driving and work, may be resumed the next day.
Risks: As with all surgery, there are risks. Risks of laser glaucoma procedures may include a short-term increase in intraocular pressure or an excessive drop in pressure. Both complications are rare and controlled with glaucoma medications. There is a small risk for cataract formation after some types of surgery.
Benefits: Failure to control glaucoma can result in destruction of the optic nerve and permanent blindness of the affected eye. Reducing or preventing raised intraocular pressure by laser therapy is effective in reducing the risk of blindness from glaucoma.
Laser Treatments for Primary Open-Angle Glaucoma
* Selective laser trabeculoplasty (SLT) reduces intraocular pressure by enhancing drainage of excess aqueous fluid. The laser increases drainage by selectively treating certain cell tissue of the trabecular meshwork. The meshwork is at the entrance of the drainage canals. SLT treatments can occasionally be repeated if necessary.
* Argon laser trabeculoplasty (ALT) reduces intraocular pressure by opening the drainage canals of the eye. In many cases, drugs will continue to be needed to maintain safe internal eye pressure after this procedure.
Laser Treatments for Narrow-Angle Glaucoma
* Laser peripheral iridotomy (LPI) reduces excessive intraocular pressure by making a small hole in the iris, the colored part of the eye. Narrow-angle glaucoma occurs when the angle between the iris and cornea, the clear front part of the eye, is too small. The hole allows the iris to move back from the cornea, opening the angle and enhancing aqueous flow.
* Laser cyclophotocoagulation is used to reduce eye pressure by treating the ciliary body, which produces aqueous fluid. The procedure is most commonly used for patients with extensive and end stage glaucoma damage that are not responding to other glaucoma surgeries.
Conventional or Incision Surgery
As noted above, conventional surgery or filtering microsurgery is used when management of glaucoma through medication and laser surgery has failed or is less desirable. Trabeculectomy is most commonly used to prevent or curtail damage to the optic nerve by reducing intraocular pressure. In this procedure, a small incision is made in the sclera of the eye (see Diagram 2) and a flap of tissue is left to cover the incision, allowing slow release of fluid from the inside the eye to its outer layers. The procedure results in the formation of a small blister-like bump called a “bleb.” The bleb is covered by the eyelid and is usually not visible. The excess fluid is carried away as it is absorbed into the bloodstream.
A new modification of trabeculectomy, is non-penetrating deep sclerectomy or viscocanalostomy, where a full-thickness hole in the eye is avoided. Instead, a very deep dissection is performed in the sclera and trabecular meshwork. Intraocular pressure is lowered as fluid oozes through a permeable thin layer of tissue that is created by the viscocanalostomy. A bleb may be formed, but it is usually smaller than one that would be formed following trabeculectomy.
In case of complicated glaucoma or patients who have had multiple surgeries, the use of a tube-shunt or seton is required. These devices, which include the Ahmed Valve, Baervedlt device, or Molteno device, have a plastic tube that is placed in the eye, which drains to an external reservoir placed outside the eye.
What to expect: Microsurgical procedures are performed in an ambulatory surgical center or on an outpatient basis at a hospital. Patients are usually given limited intravenous sedation but may be given general anesthesia. Medication may also be administered around the eye to prevent its movement. Typically, patients are relaxed and experience little if any discomfort.
Risks and benefits: The risks of incision surgery are small. Nevertheless, as with any incision, there is the risk of bleeding and infection. The eye may be red or inflamed, with discomfort and pain. In some instances, the procedure may not reduce eye pressure as intended. Loss of too much pressure can result in a loss of vision. As with laser surgeries, there are occasional instances in which the pressure is too high or too low. When this occurs, medications or additional surgeries may be needed to control the condition. In some instances, cataracts may develop. In very rare circumstances, an eye can be removed as a result of surgery. As with all procedures or medications, the risks need to be balanced with the benefits of saving vision in the affected eye. Failure to control glaucoma can result in destruction of the optic nerve and permanent blindness in the affected eye.
Success rates for glaucoma filtering surgery are about 70% to 90% for at least 1 year. In some instances, the surgically created drainage channel may “heal” or close, in which case high intraocular pressure can recur. The healing or closure of the drainage opening is a natural process that is more likely to develop in younger people. To prevent or retard closure, drugs such as mitomycin-C and 5-fluorouracil may be administered. If necessary, the surgery can be repeated in the same eye.
Wavefront Technology
Wavefront-guided LASIK is a promising new technology that provides an advanced method for measuring optical distortions in the eye. Measuring and treating these distortions goes beyond nearsighted, farsighted, and astigmatism determinations that have been used for centuries. As a result, physicians can now customize the LASIK procedure according to each individual patient’s unique vision correction needs. The treatment is unique to each eye, just as a fingerprint is unique. Wavefront systems work by measuring how light is distorted as it passes into the eye and then is reflected back. This creates an optical map of the eye, highlighting individual imperfections.
Wavefront technology functions as a roadmap for LASIK surgery, providing benefits to the patient during both the evaluation and treatment process.
- During the patient evaluation process, wavefront provides the physician comprehensive individual diagnostic information, not available using earlier technologies. Thus, before surgery even begins, the surgeon is better able to determine the appropriate course of treatment.
- During treatment, wavefront allows the surgeon to tailor the laser beam settings, making the surgical procedure itself more precise. In this way, wavefront technology offers the patients sharper, crisper, better quality vision, as well as a reduction in nighttime vision difficulties, such as halos and glare.
Wavefront technology is an adjunct tool used to enhance an already safe and effective procedure. As the most common form of vision correction surgery, LASIK has already benefited millions of patients. The increased safety and the improved quality of vision benefits of customized procedures are an important technological advancement for patients and physicians alike.
Visual Errors
For purposes of this discussion, there are two categories of visual errors or “aberrations:” second-order and higher-order.
Conventional forms of optical correction have been limited to measuring the best spherical and cylindrical visual errors (second-order aberrations), which result in myopia (shortsightedness) or hyperopia (farsightedness) and regular astigmatism (blurriness), and prescribing shperocylindrical lenses in the form of spectacles, contact lenses, and conventional refractive (LASIK) surgery to correct them. Correcting second-order aberrations has the highest impact on acuity, which is the eye’s ability to distinguish object details and shape. At the same time that conventional refractive surgery corrects major, second-order spherical errors, in many cases, it also induces some degree of minor spherical aberrations.
However, about 17 percent of optical errors are higher-order aberrations. If these are minimized, image contrast and special detail are increased. Minimizing higher-order aberrations with wavefront technology by reducing the naturally occurring ones is achievable and may be particularly beneficial to individuals with unusually large amounts of higher-order aberrations.
How Wavefront Works: The wavefront aberrometer
Light can be thought of as traveling in a series of flat sheets, known as wavefronts. To clarify the confusion about light traveling as waves instead of rays, waves are just perpendicular to light rays. These light waves are wrinkled or distorted as they pass through imperfections in the eye. These errors can be displayed on a color map of the wavefront image, which is the tool that is used to diagnose, and then determine corrections, for abberrations in the eye.
There are several ways of analyzing the optical system of the eye using wavefront technology. The most common, the Hartmann-Shack wavefront sensing method, deals with light waves as they exit the eye. In this system, the surgeon or other professional shines a small, low-intensity laser into the eye, and the patient focuses on the light. As that light scatters off of the retina (the rear-most portion of the eye) it passes through the lens, the rear surface of the cornea (the clear, crystalline front part of the eye) and the front surface of the cornea. Thus, the emerging waves of light are distorted by the imperfections in the total visual system of the eye. After leaving the eye, the light passes through an array of many small lenses in the sensing device (called an aberrometer), and is focused into spots, which are recorded by a special camera. The deviation of the spots from their ideal location provides information about focusing imperfections in the visual system.
Wavefront-Guided Treatment
The goal of wavefront-guided laser treatment is to make corrections in the surface of the cornea that compensate for errors in the total visual system. Thus, the amount of wrinkle or error in the wavefront reflected from the back of the eye, as compared to the reference wavefront that was projected into it, defines the compensating optical correction. If the wavefront is retarded in relation to the reference wavefront, the laser must remove more tissue from the part of cornea related to that pattern. If the wavefront is advanced (in front of the referenced wavefront), the laser must remove less tissue. It should be noted that wavefront treatment does induce some minor second-order spherical errors, but to a significantly lesser extent than conventional refractive surgery.
In this way, a wavefront-guided treatment is customized to the characteristics of each eye and intended to minimize higher-order aberrations so that the greatest quality of vision can be achieved.
Wavefront technology is relatively new to the United States. The U.S. Food and Drug Administration (FDA) issued its first approval of a wavefront system in August 2002, and other major US laser manufacturers are expected to receive their approvals in 2003. As the FDA approves systems and they become widely available, patients will have greater access to wavefront technology and treatment.
Wavefront technology functions as a roadmap for LASIK surgery, providing benefits to the patient during both the evaluation and treatment process.
- During the patient evaluation process, wavefront provides the physician comprehensive individual diagnostic information, not available using earlier technologies. Thus, before surgery even begins, the surgeon is better able to determine the appropriate course of treatment.
- During treatment, wavefront allows the surgeon to tailor the laser beam settings, making the surgical procedure itself more precise. In this way, wavefront technology offers the patients sharper, crisper, better quality vision, as well as a reduction in nighttime vision difficulties, such as halos and glare.
Wavefront technology is an adjunct tool used to enhance an already safe and effective procedure. As the most common form of vision correction surgery, LASIK has already benefited millions of patients. The increased safety and the improved quality of vision benefits of customized procedures are an important technological advancement for patients and physicians alike.
Visual Errors
For purposes of this discussion, there are two categories of visual errors or “aberrations:” second-order and higher-order.
Conventional forms of optical correction have been limited to measuring the best spherical and cylindrical visual errors (second-order aberrations), which result in myopia (shortsightedness) or hyperopia (farsightedness) and regular astigmatism (blurriness), and prescribing shperocylindrical lenses in the form of spectacles, contact lenses, and conventional refractive (LASIK) surgery to correct them. Correcting second-order aberrations has the highest impact on acuity, which is the eye’s ability to distinguish object details and shape. At the same time that conventional refractive surgery corrects major, second-order spherical errors, in many cases, it also induces some degree of minor spherical aberrations.
However, about 17 percent of optical errors are higher-order aberrations. If these are minimized, image contrast and special detail are increased. Minimizing higher-order aberrations with wavefront technology by reducing the naturally occurring ones is achievable and may be particularly beneficial to individuals with unusually large amounts of higher-order aberrations.
How Wavefront Works: The wavefront aberrometer
Light can be thought of as traveling in a series of flat sheets, known as wavefronts. To clarify the confusion about light traveling as waves instead of rays, waves are just perpendicular to light rays. These light waves are wrinkled or distorted as they pass through imperfections in the eye. These errors can be displayed on a color map of the wavefront image, which is the tool that is used to diagnose, and then determine corrections, for abberrations in the eye.
There are several ways of analyzing the optical system of the eye using wavefront technology. The most common, the Hartmann-Shack wavefront sensing method, deals with light waves as they exit the eye. In this system, the surgeon or other professional shines a small, low-intensity laser into the eye, and the patient focuses on the light. As that light scatters off of the retina (the rear-most portion of the eye) it passes through the lens, the rear surface of the cornea (the clear, crystalline front part of the eye) and the front surface of the cornea. Thus, the emerging waves of light are distorted by the imperfections in the total visual system of the eye. After leaving the eye, the light passes through an array of many small lenses in the sensing device (called an aberrometer), and is focused into spots, which are recorded by a special camera. The deviation of the spots from their ideal location provides information about focusing imperfections in the visual system.
Wavefront-Guided Treatment
The goal of wavefront-guided laser treatment is to make corrections in the surface of the cornea that compensate for errors in the total visual system. Thus, the amount of wrinkle or error in the wavefront reflected from the back of the eye, as compared to the reference wavefront that was projected into it, defines the compensating optical correction. If the wavefront is retarded in relation to the reference wavefront, the laser must remove more tissue from the part of cornea related to that pattern. If the wavefront is advanced (in front of the referenced wavefront), the laser must remove less tissue. It should be noted that wavefront treatment does induce some minor second-order spherical errors, but to a significantly lesser extent than conventional refractive surgery.
In this way, a wavefront-guided treatment is customized to the characteristics of each eye and intended to minimize higher-order aberrations so that the greatest quality of vision can be achieved.
Wavefront technology is relatively new to the United States. The U.S. Food and Drug Administration (FDA) issued its first approval of a wavefront system in August 2002, and other major US laser manufacturers are expected to receive their approvals in 2003. As the FDA approves systems and they become widely available, patients will have greater access to wavefront technology and treatment.
Prepare for LASIK eye surgery
Before surgery, your eye doctor takes a detailed medical history and uses specialized equipment to carefully measure your cornea, noting the shape and any irregularities.
If you wear contact lenses, you'll need to switch to glasses full time a few weeks before this exam. Contact lenses can distort the shape of your cornea, which could lead to inaccurate measurements and a poor surgical outcome.
Skip your eye makeup and eye cream on the day before and the day of your surgery. Your doctor may also instruct you to clean your eyelashes daily or more often in the days leading up to surgery, to remove debris and minimize your risk of infection.
You'll need to have someone drive you to and from your surgery. Immediately after surgery, you might still feel the affects of medicine given to you before surgery and your vision may be blurry.
Refractive surgery is usually considered elective surgery — which means it isn't vital to your health and well-being. For this reason, Medicare and most insurance companies won't cover the cost of the surgery. So be prepared to pay out-of-pocket for your expenses.
If you wear contact lenses, you'll need to switch to glasses full time a few weeks before this exam. Contact lenses can distort the shape of your cornea, which could lead to inaccurate measurements and a poor surgical outcome.
Skip your eye makeup and eye cream on the day before and the day of your surgery. Your doctor may also instruct you to clean your eyelashes daily or more often in the days leading up to surgery, to remove debris and minimize your risk of infection.
You'll need to have someone drive you to and from your surgery. Immediately after surgery, you might still feel the affects of medicine given to you before surgery and your vision may be blurry.
Refractive surgery is usually considered elective surgery — which means it isn't vital to your health and well-being. For this reason, Medicare and most insurance companies won't cover the cost of the surgery. So be prepared to pay out-of-pocket for your expenses.
Risks
As with any surgery, refractive surgery carries risks, including:
* Undercorrections. If the laser removes too little tissue from your eye, you won't get the vision results you were hoping for. Undercorrections are more common for people who are nearsighted. You may need another refractive surgery (enhancement surgery) within a year to remove more tissue.
* Overcorrections. It's also possible that the laser will remove too much tissue from your eye. Overcorrections may be more difficult to fix than undercorrections.
* Astigmatism. Astigmatism can be caused by uneven tissue removal. This sometimes occurs if your eye moves too much during surgery. It may require additional surgery.
* Glare, halos and double vision. After surgery you may have difficulty seeing at night. You might notice glare, halos around bright lights or double vision. Sometimes these signs and symptoms can be treated with eyedrops that contain a type of corticosteroid, but sometimes a second surgery is required.
* Dry eyes. For the first six months or so after your surgery, as your eyes heal they might feel unusually dry. Your eye doctor might recommend that you use eyedrops during this time. If you experience severe dry eye, you could opt for another procedure to get special plugs put in your tear ducts to prevent your tears from draining away from the surface of your eyes.
* Flap problems. Folding back or removing the flap from the front of your eye during surgery can cause complications, including infection, tearing and swelling. The flap removed during PRK may grow back abnormally.
If you're considering LASIK eye surgery, talk to your doctor about your questions and concerns. He or she can explain how the surgery might benefit you and help put the risks in perspective.
* Undercorrections. If the laser removes too little tissue from your eye, you won't get the vision results you were hoping for. Undercorrections are more common for people who are nearsighted. You may need another refractive surgery (enhancement surgery) within a year to remove more tissue.
* Overcorrections. It's also possible that the laser will remove too much tissue from your eye. Overcorrections may be more difficult to fix than undercorrections.
* Astigmatism. Astigmatism can be caused by uneven tissue removal. This sometimes occurs if your eye moves too much during surgery. It may require additional surgery.
* Glare, halos and double vision. After surgery you may have difficulty seeing at night. You might notice glare, halos around bright lights or double vision. Sometimes these signs and symptoms can be treated with eyedrops that contain a type of corticosteroid, but sometimes a second surgery is required.
* Dry eyes. For the first six months or so after your surgery, as your eyes heal they might feel unusually dry. Your eye doctor might recommend that you use eyedrops during this time. If you experience severe dry eye, you could opt for another procedure to get special plugs put in your tear ducts to prevent your tears from draining away from the surface of your eyes.
* Flap problems. Folding back or removing the flap from the front of your eye during surgery can cause complications, including infection, tearing and swelling. The flap removed during PRK may grow back abnormally.
If you're considering LASIK eye surgery, talk to your doctor about your questions and concerns. He or she can explain how the surgery might benefit you and help put the risks in perspective.
After surgery
Immediately after surgery, your eye may burn or itch and be watery. You'll probably have blurred vision. You may be given pain medication or eyedrops to keep you comfortable for several hours after the procedure. Your eye doctor might also ask you to wear a shield over your eye at night until your eye heals.
Typically you're able to see the day of your surgery, but your vision won't necessarily be better right away. Expect your vision to improve over the next two to three months. Most people who have refractive surgery eventually attain 20/25 or better vision. Your chances for improved vision are based, in part, on how good your vision was before surgery.
Other types of refractive surgery
Your eye doctor may recommend another type of refractive surgery if you're not a good candidate for LASIK eye surgery. These include:
*
Photorefractive keratectomy (PRK). PRK is sometimes used if you have a low to moderate degree of nearsightedness or farsightedness, or if you have nearsightedness with astigmatism. PRK removes the thin surface layer of your cornea (epithelium). Your eye surgeon then uses a laser to flatten your cornea or make its curve steeper.
The exposed surface of your cornea repairs itself, assisted by a contact lens you wear as a bandage over your eye for three or four days after surgery. You might have eye pain for a few days until your cornea heals. It generally takes up to a week for your eye to regenerate the surface tissue that was removed. During this time you'll notice variations in your vision. It may take three to six months before your vision improves completely. Most people undergoing PRK have both eyes done on the same day.
PRK has become less common in recent years because more eye surgeons prefer the LASIK procedure. Healing after LASIK is more predictable and usually involves less discomfort and scarring.
*
Laser epithelial keratomileusis (LASEK). LASEK is similar to LASIK eye surgery and might be an option if you aren't eligible for LASIK. During a LASEK procedure, a much thinner layer — the surface layer (epithelium) — of your cornea is folded back to allow the laser to focus on parts of your cornea that need reshaping. The epithelial flap is then replaced.
If you have very thin corneas, you might be a better candidate for LASEK because the procedure allows your doctor to remove less of your cornea. People who play sports or have jobs that carry a high risk of eye injuries might also prefer LASEK because a thinner flap means less damage to your vision should the flap be torn before it can heal. As with LASIK, the LASEK procedure can be done on both eyes on the same day.
Typically you're able to see the day of your surgery, but your vision won't necessarily be better right away. Expect your vision to improve over the next two to three months. Most people who have refractive surgery eventually attain 20/25 or better vision. Your chances for improved vision are based, in part, on how good your vision was before surgery.
Other types of refractive surgery
Your eye doctor may recommend another type of refractive surgery if you're not a good candidate for LASIK eye surgery. These include:
*
Photorefractive keratectomy (PRK). PRK is sometimes used if you have a low to moderate degree of nearsightedness or farsightedness, or if you have nearsightedness with astigmatism. PRK removes the thin surface layer of your cornea (epithelium). Your eye surgeon then uses a laser to flatten your cornea or make its curve steeper.
The exposed surface of your cornea repairs itself, assisted by a contact lens you wear as a bandage over your eye for three or four days after surgery. You might have eye pain for a few days until your cornea heals. It generally takes up to a week for your eye to regenerate the surface tissue that was removed. During this time you'll notice variations in your vision. It may take three to six months before your vision improves completely. Most people undergoing PRK have both eyes done on the same day.
PRK has become less common in recent years because more eye surgeons prefer the LASIK procedure. Healing after LASIK is more predictable and usually involves less discomfort and scarring.
*
Laser epithelial keratomileusis (LASEK). LASEK is similar to LASIK eye surgery and might be an option if you aren't eligible for LASIK. During a LASEK procedure, a much thinner layer — the surface layer (epithelium) — of your cornea is folded back to allow the laser to focus on parts of your cornea that need reshaping. The epithelial flap is then replaced.
If you have very thin corneas, you might be a better candidate for LASEK because the procedure allows your doctor to remove less of your cornea. People who play sports or have jobs that carry a high risk of eye injuries might also prefer LASEK because a thinner flap means less damage to your vision should the flap be torn before it can heal. As with LASIK, the LASEK procedure can be done on both eyes on the same day.
Tuesday, September 2, 2008
A Brief Note on LASIK
LASIK surgery, a laser eye surgery that is safe, may be used to improve the eyesight of millions who suffer with various sight diagnosis. Laser Assisted Situ Karatomileusis, or LASIK, procedures involve the use of a monochromatic beam that reshapes the cornea of the eye. The machines and laser beams used in these procedures are regulated by the Federal Food and Drug Administration (FDA), insuring patients that the process and lasers used are safe. The FDA oversees the selling of medical equipment in the United States. This means that before doctors may purchase a particular medical instrument or device, this piece must be approved by the FDA, who analyze, thoroughly examine, and test the equipment, to determine the equipment to be safe and to be beneficial to the patient. Once an approval for any device is reached, doctors may have access to the instrument.
The procedure of laser surgery for the eyes has grown in popularity, and doctors use an approved refractive laser system for treating various optical conditions. The most common procedures are used to treat refractive errors such as myopia, hyperopia, and astigmatism, which are conditions related to focus. These diagnosis are commonly referred to as farsightedness, nearsightedness, and various astigmatisms. Other optical diseases are not yet being treated with laser surgery for eyes.
Safe LASIK surgeries can even be performed in a doctor's office. The entire procedure may take less than thirty minutes. There are many precautions used to ensure safety and to prevent complications, such as infection. First, numbing medicines are used to prevent extreme discomfort and irritation to the eyes. Doctors will thoroughly clean the eye and surrounding area, removing any possible articles which could cause further irritations. There are simple devices used to keep the eyelids open . Before the procedure, doctors may also prescribe a mild sedative to patients, helping them to relax and stay calm, increasing the likelihood of success.
The actual process of laser surgery for eyes utilizes an intense beam to open a flap in the cornea. The doctor places a ring around the eye during the surgery, where pressure causes the eye to come forward. At this point, the doctor will begin to use various intense beams to open the cornea and reshape it, allowing refractive light to be more focused, improving vision. After the surgical event, there will be a protective covering which should be used to keep patients from rubbing the area, which may be itching and burning and there may be eye drops prescribed, to keep the area clean. Excessive tearing or watering may occur with some patients and patients should also consult with doctors about all post-op instructions.
Even though laser eye surgery that is safe can help restore vivid eyesight, LASIK surgery for eyes is not for everyone. There are certain conditions which may prohibit this high-tech laser beam procedure. Teenagers under the age of eighteen are not good candidates for LASIK procedures. Young people may still grow, and the eye and cornea may alter with time and growth. There are also those who have a condition called refractive instability. Refractive instability is a condition that causes the eye's ability to focus light to change often, making this diagnosis impractical for this procedure. Also, those who are pregnant, who have fluctuating hormones, diabetes, or other diseases which prevent healing, should not consider this process. Anyone with an autoimmune diagnosis will also be advised against taking risks with surgical procedures.
There are different methods used in LASIK surgeries. Those considering LASIK should obtain a quick education about the surgery and research several different doctors who work with laser equipment. While the actual equipment utilized during a procedure is considered safe by the FDA, doctors and their practices are not actively regulated. Also, costs for laser eye surgery that is safe is also not overseen by the government, so patients will want to make sure and pay competitive prices and that they are receiving the entire treatment paid for. With the popularity of laser surgery for eyes, the industry has grown very competitive. Those investigating or considering LASIK procedures will want to avoid advertising campaigns that sound too good to be true, and find reputable doctors to ensure that the laser eye surgery that is safe, truly is.
The Bible tells us, "Happy is the man that findeth wisdom, and the man that getteth understanding. For the merchandise of it is better than the merchandise of silver, and the gain thereof than fine gold." (Proverbs 3:13-14) No one should be quick to rush into any type of surgery, even a laser eye surgery that is safe. The wise person will seek to get knowledge about any medical procedure before taking risks with the body that God has created and given. It is ultimately the responsibility of the patient to determine what is best for their own bodies and what risks involved will make a medical procedure worth those risks. Spend time in prayer and seek the counsel of others before going forward with laser surgery for eyes.
The procedure of laser surgery for the eyes has grown in popularity, and doctors use an approved refractive laser system for treating various optical conditions. The most common procedures are used to treat refractive errors such as myopia, hyperopia, and astigmatism, which are conditions related to focus. These diagnosis are commonly referred to as farsightedness, nearsightedness, and various astigmatisms. Other optical diseases are not yet being treated with laser surgery for eyes.
Safe LASIK surgeries can even be performed in a doctor's office. The entire procedure may take less than thirty minutes. There are many precautions used to ensure safety and to prevent complications, such as infection. First, numbing medicines are used to prevent extreme discomfort and irritation to the eyes. Doctors will thoroughly clean the eye and surrounding area, removing any possible articles which could cause further irritations. There are simple devices used to keep the eyelids open . Before the procedure, doctors may also prescribe a mild sedative to patients, helping them to relax and stay calm, increasing the likelihood of success.
The actual process of laser surgery for eyes utilizes an intense beam to open a flap in the cornea. The doctor places a ring around the eye during the surgery, where pressure causes the eye to come forward. At this point, the doctor will begin to use various intense beams to open the cornea and reshape it, allowing refractive light to be more focused, improving vision. After the surgical event, there will be a protective covering which should be used to keep patients from rubbing the area, which may be itching and burning and there may be eye drops prescribed, to keep the area clean. Excessive tearing or watering may occur with some patients and patients should also consult with doctors about all post-op instructions.
Even though laser eye surgery that is safe can help restore vivid eyesight, LASIK surgery for eyes is not for everyone. There are certain conditions which may prohibit this high-tech laser beam procedure. Teenagers under the age of eighteen are not good candidates for LASIK procedures. Young people may still grow, and the eye and cornea may alter with time and growth. There are also those who have a condition called refractive instability. Refractive instability is a condition that causes the eye's ability to focus light to change often, making this diagnosis impractical for this procedure. Also, those who are pregnant, who have fluctuating hormones, diabetes, or other diseases which prevent healing, should not consider this process. Anyone with an autoimmune diagnosis will also be advised against taking risks with surgical procedures.
There are different methods used in LASIK surgeries. Those considering LASIK should obtain a quick education about the surgery and research several different doctors who work with laser equipment. While the actual equipment utilized during a procedure is considered safe by the FDA, doctors and their practices are not actively regulated. Also, costs for laser eye surgery that is safe is also not overseen by the government, so patients will want to make sure and pay competitive prices and that they are receiving the entire treatment paid for. With the popularity of laser surgery for eyes, the industry has grown very competitive. Those investigating or considering LASIK procedures will want to avoid advertising campaigns that sound too good to be true, and find reputable doctors to ensure that the laser eye surgery that is safe, truly is.
The Bible tells us, "Happy is the man that findeth wisdom, and the man that getteth understanding. For the merchandise of it is better than the merchandise of silver, and the gain thereof than fine gold." (Proverbs 3:13-14) No one should be quick to rush into any type of surgery, even a laser eye surgery that is safe. The wise person will seek to get knowledge about any medical procedure before taking risks with the body that God has created and given. It is ultimately the responsibility of the patient to determine what is best for their own bodies and what risks involved will make a medical procedure worth those risks. Spend time in prayer and seek the counsel of others before going forward with laser surgery for eyes.
Choosing Your Surgeon
When choosing a surgeon to perform your laser eye surgery there are many factors that you will want to take into consideration:
*
Experience
*
Comprehensive Skills
*
A Dedication to Refractive Surgery
*
State of the Art Equipment
*
Personality, Style, and an Expert Staff
EXPERIENCE
The surgeon you choose should have been performing refractive surgeries for at least three years and performed no fewer then 250 refractive vision correction procedures in the last 12 months. Be sure to speak with recent and past patients that have had the surgery performed by your surgeon. Your surgeon should easily give you a list of 25 or more patients to contact.
SKILLS
Make sure your surgeon is qualified to perform your laser eye surgery. Ask him/her which techniques he/she has been trained in. Your surgeon should have the skills to perform more then one type of refractive surgery. Be wary of surgeons that only offer one or two of the available techniques to correct vision problems. Your surgeon needs to be able to offer you the best surgery available for your condition. Additionally, your surgeon needs to have the skills to perform any enhancements to your eyes that may be required after your initial refractive surgery.
DEDICATION
Is your surgeon dedicated to performing laser eye surgeries? Choosing a surgeon that only performs a couple of procedures a week may not have the experience or skills to perform the surgery required for your vision problems. Additionally, you should ask your surgeon which refractive surgery associations and organizations in which he or she belongs. The manufacturers of the laser surgery equipment also provide documentation to the surgeon for any training provided to him/her.
PERSONALITY
Does your surgeon make you feel comfortable? Are you able to ask your surgeon questions and have them answered in a manner that you understand? The answers to both of these questions should be yes. Your vision is invaluable and you must feel at ease with your surgeon on a personal level. Your surgeon should readily be open to questions and answer them to your satisfaction in an honest and caring manner.
EQUIPMENT
Finally, you want to insure that your surgeon's office is equipped with the latest equipment and manned by an experienced staff. Be sure to verify that your surgeon is using a laser that has been approved by the FDA. Some surgeons have been known to use lasers that have been re-imported, custom-made, or home-made. Furthermore, ask your surgeon if the FDA approved laser he/she is using has been properly serviced and maintained.
STAFF
Take the time to interact with your surgeon's office staff before your procedure. A staff that is dedicated to refractive surgery should be able to take care of your needs and insure that your experience is a rewarding one. There are three different types of eye care professionals usually involved in a person's eye care
*
Experience
*
Comprehensive Skills
*
A Dedication to Refractive Surgery
*
State of the Art Equipment
*
Personality, Style, and an Expert Staff
EXPERIENCE
The surgeon you choose should have been performing refractive surgeries for at least three years and performed no fewer then 250 refractive vision correction procedures in the last 12 months. Be sure to speak with recent and past patients that have had the surgery performed by your surgeon. Your surgeon should easily give you a list of 25 or more patients to contact.
SKILLS
Make sure your surgeon is qualified to perform your laser eye surgery. Ask him/her which techniques he/she has been trained in. Your surgeon should have the skills to perform more then one type of refractive surgery. Be wary of surgeons that only offer one or two of the available techniques to correct vision problems. Your surgeon needs to be able to offer you the best surgery available for your condition. Additionally, your surgeon needs to have the skills to perform any enhancements to your eyes that may be required after your initial refractive surgery.
DEDICATION
Is your surgeon dedicated to performing laser eye surgeries? Choosing a surgeon that only performs a couple of procedures a week may not have the experience or skills to perform the surgery required for your vision problems. Additionally, you should ask your surgeon which refractive surgery associations and organizations in which he or she belongs. The manufacturers of the laser surgery equipment also provide documentation to the surgeon for any training provided to him/her.
PERSONALITY
Does your surgeon make you feel comfortable? Are you able to ask your surgeon questions and have them answered in a manner that you understand? The answers to both of these questions should be yes. Your vision is invaluable and you must feel at ease with your surgeon on a personal level. Your surgeon should readily be open to questions and answer them to your satisfaction in an honest and caring manner.
EQUIPMENT
Finally, you want to insure that your surgeon's office is equipped with the latest equipment and manned by an experienced staff. Be sure to verify that your surgeon is using a laser that has been approved by the FDA. Some surgeons have been known to use lasers that have been re-imported, custom-made, or home-made. Furthermore, ask your surgeon if the FDA approved laser he/she is using has been properly serviced and maintained.
STAFF
Take the time to interact with your surgeon's office staff before your procedure. A staff that is dedicated to refractive surgery should be able to take care of your needs and insure that your experience is a rewarding one. There are three different types of eye care professionals usually involved in a person's eye care
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