慎做近视眼激光的十条理由（英文）

UPDATED 8/27/04 TEN COMMON SENSE REASONS WHY YOU SHOULD NOT HAVE LASIK by Ariel Berschadsky After years of dealing with the hassle of spectacles and contact lenses, you’ve decided to reward yourself by having Lasik. You’ve read the glowing reports in the media about the wonders of this “state of the art” procedure and your ophthalmologist has just pronounced you “a perfect candidate.” It is at this time, more than at any other time in your life, that you must pause, stand back from the excitement of the moment, and reflect deeply on what you are about to do. Lasik will permanently alter the optics and physiology of your eyes. Most likely things will go well. But there is a significant chance, much greater than many ophthalmologists realize or will publicly admit, that your eyes will be irreversibly damaged. The results could be devastating. When considering elective surgery one must ask if the benefits truly outweigh the risks involved. You’ve heard a lot about the benefits, no doubt from the surgeon who stands to gain financially by operating on your eyes. But you owe it to yourself to take a few minutes to read the rest of this document in order to become better informed about Lasik’s risks. Once you understand these risks, you may conclude that the prudent course of action is to avoid the Lasik fad until the procedure has fully matured, withstood the test of time, and been proven safe. After all, we’re talking about your eyes. 1. The True Degree of Risk is Unclear and is Being Downplayed. Before surgery, patients are typically told that the risk of complications from Lasik is 1%, and even lower in the hands of an experienced surgeon (such as the one trying to sell you the procedure). For starters, one must realize that the risk being referred to is for each eye, so the combined risk that permanent damage will occur to at least one eye is, by these figures, actually 2%. Doesn’t sound so good anymore? Read on… During the process of obtaining Food and Drug Administration (FDA) Preliminary Market Approval (PMA) for its LADARVision Excimer Laser System, Alcon Corporation admitted that 22.8% of Lasik patients complained of light sensitivity post-operatively, 7.1% now suffered from headaches, 31.9% had glare symptoms, and 32% now experienced night driving difficulties.1 The FDA nevertheless approved the LADARVision laser for commercial use,2 despite the fact that 12.7% of LADARVision patients stated that they experienced “worse” or “significantly worse” quality of vision, as reported in the PMA.3 One recent study states that complications from Lasik surgery occur in approximately 4% of eyes operated on.4 These complications often produce 1 See Premarket Approval Application #P970043/S5, available through Dockets Management Branch (HFA-305), FDA, p.19. 2 Approved May 9, 2000. See Docket #OOM- 1592, p.1. 3 See Premarket Approval Application, p. 23. 4 See Sugar A. et. al., LASIK for Myopia and UPDATED 8/27/04 vision-distorting irregular astigmatism. Unlike regular astigmatism, which is correctable with glasses, irregular astigmatism cannot be corrected with glasses. Rigid Gas Permeable (RGP) contact lenses offer some hope to those suffering from Lasik-Induced Irregular Astigmatism (LIIA) because they provide a smooth surface that masks corneal irregularities by permitting pooling of tears beneath the lens. However, due to the flattening of the cornea following Lasik, it is nearly impossible to find RGP lenses that will stay centered over the pupil and will not rub against the interface between treated and untreated areas of the cornea. The result is that RGP lenses are extremely uncomfortable for the post-refractive and therefore do not offer a viable solution to irregular astigmatism. New laser techniques involving eye tracking are being developed to treat irregular astigmatism,5 but they are still in the experimental stages, are yielding mixed results, and may never be precise enough to correct LIIA.6 Astigmatism: Safety and Efficacy, OPHTH., Vol. 109, pp.175-87, 2002. 5 These include Alcon-Summit- Autonomous/Zeiss’s CustomCornea System, Visx’s WaveScan Wavefront Analysis System based on Hartmann-Shack principles, Bausch & Lomb’s Zyoptix System, the University of Dresden’s Wavefront Analyzer, Tracey Technologies’ Visual Function Analyzer, Wavefront Sciences/Asclepion-Meditec’s Complete Ophthalmic Aberrometer System, Nidek’s Optical Path Difference Retinoscopy- Based System, and Laser Sight Technologies’ CustomEyes System. All of these systems are still in clinical trials. See Michael Moretti, Laser Makers Riding the Wavefront in Corneal Ablation Push, BBI NEWSLETTER, Vol. 24(2), Feb. 1, 2001, p.41. 6 See Steven Wilson, M.D., Chief Medical Editor, “The Complications of Raising Expectations,” REV. REFRACT. SURG., p.3 Many ophthalmologists are unaware of Lasik’s true risks because they tend to avoid patients with post-Lasik complications, given that it is less profitable to treat such a patient than to operate on a fresh candidate. These doctors therefore never gain an accurate awareness of the extent of damage that is being done by Lasik. Their ignorance is compounded by their unfamiliarity with organizations such as SurgicalEyes and LasikInfoCenter, which are dedicated to providing emotional and informational support to thousands of people suffering from refractive surgery complications. 2. Lasik Technology is in its Infancy. The refractive surgical community depends financially on the average individual’s tendency to get swept up by fads. This natural human tendency provides refractive surgeons and medical device manufacturers with large numbers of patients on whom to refine their surgical techniques and devices. At present, for example, there is no consensus on what kind of excimer laser provides optimal results. Nidek’s single beam laser follows a very different approach to ablating corneal tissue from that of Visx’s broad beam laser, yet both are touted as being “state of the art.” Many surgeons cut the Lasik flap from side to side (a nasal hinge) because they feel that this method transcects (“… there is a bothersome trend in which patients with complications from LASIK or PRK are told that [custom corneal ablation] will be possible “within a year”… this is far from becoming a reality… these eyes are exponentially more complex than [those with corneas] that are essentially smooth… custom corneal ablation for irregular astigmatism is just as likely to be a decade away from now as a year from now.”). UPDATED 8/27/04 fewer nerves.7 Other surgeons pronounce themselves experts in using the Hansatome microkeratome, which cuts a supposedly superior “up-down” flap.8 The field of refractive surgery is still so young that many ophthalmologists develop and market their own surgical instruments to perform various procedures, such as cutting, lifting, or irrigating flaps. Perhaps some of their enthusiasm for Lasik stems from the goal of “creating rapid profits by promulgating sales of surgical equipment and adopting new surgical techniques,” as one eminent refractive surgeon has speculated.9 7 See Nicole Nader, Smaller Flap, Nasal Hinge Reduce Lasik-Induced Dry Eye Symptoms, OCULAR SURG. NEWS, 2/15/04 (“The nerve trunks in the cornea enter nasally and temporally,” Dr. Donnenfeld said. “A superior hinge transects both areas of the cornea where innervation occurs, severing both arms of the neuroplexus.” A nasal hinge transects only one of these nerve trunks, the temporal arm.) 8 A recent study concluded that the Hansatome microkeratome does not always produce a corneal flap of the intended thickness. Flaps that are too thin can lead to flap wrinkles, which in turn cause devastating irregular astigmatism. See Rengin Yildirim, M.D. et al, Reproducibility of Corneal Flap Thickness in LASIK Using the Hansatome Microkeratome, J. CATARACT REFRACT. SURG. (2000) Vol. 26, pp. 1729-32. See also Vikram D. Durairaj, M.D. et al, Predictability of Corneal Flap Thickness and Tissue Laser Ablation in LASIK, OPHTH. (2000), Vol. 107, pp. 2140-3 (“Actual flap thickness was significantly different from predicted flap thickness.”). 9 See George O. Waring III, MD, FRCOphth, A Cautionary Tale of Innovation in Refractive Surgery, ARCH OPHTH., Vol. 117(8), Aug. 1999. Dr. Waring has stated that he would not be willing to take even a 1 in 500,000 risk on his own eyes through elective refractive surgery. See Jeffrey Weiss, Demand High for RK Eye Surgery – Critics Say Glasses, Contacts Work Marketers recognize a type of consumer known as the “early adopter,” someone who enjoys buying products with the latest technology. Refractive surgeons are also keenly aware of this, and most medical texts about Lasik contain one or more chapters on how to boost profits by targeting such consumers. The discussion of marketing strategies in medical texts speaks volumes about the commercialized nature of this field of “medicine.” There is no harm in being an early adopter when one is dealing with a video game or laptop computer. But does this approach make sense with an irreversible surgical procedure on one’s eyes? Dr. George Waring, Editor-in-Chief of the Journal of Refractive Surgery, answers this question best when he writes that “… we proceed with active teaching of hundreds or thousands of ophthalmologists to use a technique that we are simultaneously figuring out how to do – including the identification of complications and statistical outcomes. Is it not safer for patients and more rational for the profession to proceed in a graduated manner, refining the techniques and improving the results on smaller numbers of patients (or in the laboratory), and saving our mass education for the time when we have worked the bugs out of the technique and have acquired reasonably quantitative descriptions of safety and efficacy?”10 Other leading refractive surgeons concur that Lasik has not yet been Best, Doctors Just Trying to Enrich Themselves, SEATTLE TIMES, Jul. 12, 1993, at A4. 10 George O. Waring, III, MD, FACS, FRCOphth, Editorial, J. REFRACT. SURG., Vol. 12(3), Mar./Apr. 1996. UPDATED 8/27/04 perfected.11 One group writes that “As the technology and techniques improve, we should develop a better understanding of the importance of laser- tissue interactions, corneal wound healing, and the role of pharmacologic agents in modulating refractive outcomes. These advances should allow PRK and LASIK to become more predictable with fewer complications.”12 Do you want your eyes to be the ones to help these doctors learn how to perform Lasik more safely and successfully? 3. Lasik Induces Optical Aberrations that are Poorly Understood by Ophthalmologists. Refractive surgery tries to eliminate spherical and cylindrical defocus, the most important optical aberrations. However, this approach ignores the fact that the eye has significant higher-order aberrations. According to Dr. Raymond Applegate of the Department of Ophthalmology of the University of Texas Health Science Center, these naturally occurring higher-order aberrations, combined with large increases in the eye’s higher-order aberrations induced by refractive surgery, can decrease visual performance despite the elimination of spherocylindrical errors. Surgically-induced higher-order 11 Karl G. Stonecipher, M.D., Wavefront Technology: Reality Beneath the Hype, REV. OPTH, Apr. 2000 (asking “[W]ill wavefront technology help us to maintain prolate corneas? It should, when used in conjunction with the new breed of excimer lasers, which we’re just starting to see.”) 12 Edward E. Manche, Jonathan D. Carr, Weldon W. Haw, and Peter S. Hersh, Excimer Laser Refractive Surgery, WESTERN J. MED., Jul. 1, 1998, Vol. 169(1). aberrations have received less attention than the correction of defocus errors despite their importance to optimal visual performance.13 Moreover, the normal cornea is relatively trouble-free whereas the post- refractive cornea frequently has a more aberrated optical performance. It is often unstable and its optical performance deteriorates at night or in patients with larger-than-average pupils. Contact lenses and spectacles do not permanently alter the physiologic optics of the eye. Refractive surgery does. According to Dr. Leo Maguire of the Mayo Clinic, “When one alters irreversibly the most trouble-free component of the human visual system, one runs the risk of compounding the visual aberration caused by components of the visual system that characteristically show dysfunction with age (the lens and macula).”14 Dr. Maguire worries about how many refractive patients who can compensate for their aberrated cornea will be able to do so when the lens and macula develop age-related changes. How much sooner will they require cataract surgery or visual aids for macular degeneration?15 Another reason why the eye’s optics are degraded by Lasik is that excimer lasers were designed by engineers who assumed that the cornea is spherical rather than prolate.16 According to Dr. 13 See Raymond A. Applegate, OD, PhD & Howard Howland, PhD, Refractive Surgery, Optical Aberrations, and Visual Performance, J. REFRACT. SURG., Vol. 13, May/Jun. 1997. 14 See Leo J. Maguire, Mayo Clinic, Keratorefractive Surgery, Success, and the Public Health, AM. J. OPHTH., Vol. 117(3), Mar. 1994. 15 See id. 16 The normal cornea is prolate, which means that it is steepest in the center and gets gradually UPDATED 8/27/04 Jack Holladay, McNeese Professor of Ophthalmology at the University of Texas Medical School, these engineers further assumed that their job was to reshape a steep sphere into a flat sphere, rather than to reshape a steep prolate into a flatter prolate. As a result, excimer lasers reshape prolate corneas into oblate ones, a shape that is optically worse because now peripheral rays are bent more powerfully, causing more pronounced spherical aberrations when the pupil dilates. This problem to some extent affects every patient who undergoes an excimer laser procedure.17 A final optical ramification of Lasik that is poorly understood by most ophthalmologists is that following Lasik the eyes must focus and converge entirely unaided. However, after years of adaptation to the prismatic effect of myopia-correcting glasses, many eyes will have difficulty working together unaided. This problem of visual fusion can be compounded if either eye experiences even a slight decrease in vision due to a post-Lasik complication. If the eyes are unable to adapt after Lasik, the post-refractive patient will have difficulty reading and will experience constant eye strain. Dr. Holladay concludes by writing that “We are actually ruining the optics of the eye when we perform Lasik. That’s fine when the pupil is small, but as it gets larger, such as in nighttime conditions, this becomes a problem.”18 flatter in the periphery. An oblate cornea is flatter in the center than the normal cornea. 17 See Jack Holladay, MD, MSEE, FACS, What We Should Really Tell Lasik Patients, REV. OPHTH., May 1999. 18 Eye on Technology: New Procedure, Product Refines Lasik, INTL. SOC. REFRACT. SURG. – EYE2EYE, Jul. 2000, p. 6. 4. Lasik Reduces Contrast Sensitivity. Most people will never know what contrast sensitivity is unless they lose it as the result of Lasik. An example of diminished contrast sensitivity is that someone who is walking towards you in a situation where he is lit from behind appears as a dark silhouette. Pre-Lasik, his facial features would have been easily identifiable. Seeing a white rabbit against the snow also becomes more difficult. Loss of contrast sensitivity is permanent and to varying degrees affects everybody who undergoes Lasik, as various studies have concluded. • A study performed for the London Centre for Refractive Surgery following up on patients two to seven years after refractive surgery determined that 58% failed a contrast sensitivity test for night driving.19 • A study at Germany's Tübingen University found that more than 70% of post-refractives failed a night vision test – a requirement in Germany for receiving a driver's license.20 • The U.K. Transportation Research Laboratory concluded that due to loss of contrast sensitivity, at night 80% of post- refractives can’t see a traffic sign at 55 meters, and 40% still can’t see the sign at 15 meters.21 • The Canadian Medical Association has added laser eye surgery to a list of 19 See Carol Hilton, Studies Show Compromised Night Vision an Undetected Complication of Laser Eye Surgery, MED. POST, Jun. 6, 2000 (citing research performed by Dr. William Jory, Consultant Surgeon for the London Centre for Refractive Surgery). 20 See Louise Elliott, Canadian Medical Association Says Laser Eye Surgery Can Pose Driving Risk, CANADIAN PRESS, Aug. 27, 2000. 21 See id. UPDATED 8/27/04 risk factors for unsafe driving, after finding a decrease of night vision in between 30 and 60% of laser eye patients.22 • A report by the American Academy of Ophthalmology concluded that “… side effects such as… reduced contrast sensitivity occur relatively frequently.”23 Why does this happen? One hypothesis is that some of the laser’s energy goes beneath the targeted ablation to the corneal stroma and disturbs the fibrils.24 However, there are other hypotheses and no clear answers. Perhaps you are wondering why this side effect of Lasik has gone largely unnoticed in the United States. The reason is that, although contrast sensitivity tests are easy to administer both pre- and post-operatively, they consume more time than most ophthalmologists are willing to spend with their patients. If refractive surgeons took the time to perform all the recommended diagnostic tests, they would be spending several hours with each patient and the procedure would quickly become uneconomical for them. Therefore, they generally only spend about one or two hours giving their patients a stripped-down pre-operative evaluation. Issues such as the effect of Lasik on contrast sensitivity get lost in 22 See id. 23 See Laser In Situ Keratomileusis for Myopia and Astigmatism: Safety and Efficacy, A Report by the American Academy of Ophthalmology, OPHTH., pp.175-87, Sep. 19, 2001. 24 See id. See also, Maxine Lipner, Inside Lasik – First on the Endothelial Cell Block, EYEWORLD, Sep. 2000. (noting recent studies indicating endothelial cell damage resulting from excimer laser radiation). the rush to put more patients through the Lasik mill.25 5. Lasik Reduces the Cornea’s Structural Stability. The cornea has a natural tendency to become thinner with age.26 Combine this with the surgical removal of corneal tissue through Lasik, and there can potentially be serious pr