IMPORTANT NOTE:  This page was originally published at   EyeKnowWhy.com   Because we expected financial pressures to stop its publication we copied the pages and placed them here for you to be able to access.  As expected,   EyeKnowWhy.com  no longer exists.  Though the data here is now aging, it is still quite relevant despite all the Hype about the New And Improved Laser Surgery.  (Some of the links may also no longer be usable).  

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EyeKnowWhy Site Highlights

What This Site Is About

What is 'vision correction surgery'? Does a patient's statement that they no longer wear glasses mean they have excellent or perfect vision? What does 20/20 really mean? What does "safe" and "effective" really mean? It's time to become an informed consumer. This site presents a detailed view of refractive surgery, and covers extensively the refractive surgery industry that markets refractive surgery procedures such as RK (Radial Keratotomy), PRK (Photorefractive Keratectomy), LASIK (Laser assisted In-situ Keratomileusis)and many other procedures collectively known as vision 'correction' surgery to the public. EyeKnowWhy uses the term Refractive Surgery throughout this site to refer to all 'correction' surgeries. Whenever you see a word in single quotes ('), think "For lack of a better word" or "euphemism". These are EyeKnowWhy opinions and everyone is free to disagree. References have been provided for your own research.

But keep a few quotes in mind as you evaluate this site, as well as the statements and conclusions of other sites and references you encounter on the web and at your public and medical school library.:

"Everybody has an opinion, this is just one." EyeKnowWhy, 1997.

"You can call it haze, trace, clouding, or insignificant, but it's still a scar." EyeKnowWhy, 1997

"Complications may be rare, but if it happens to you, the chances are 100%." Dr. Walter Stark, Johns Hopkins Medical School, as quoted in Consumer Reports, Feb. 1994, "Surgery Instead of Glasses?"

"When you burn a silicon wafer with the excimer laser and the etching doesn't turn out right, you can throw it away and start over. You can't do that with a cornea." EyeKnowWhy, 1997

"It's the same each time with progress. First they ignore you, then they say you're mad, then dangerous, then there's a pause and then you can't find anyone who disagrees with you." - Tony Benn (b. 1925), British Labour politician. Quoted in: Observer (London, 6 Oct. 1991).

You are welcome to excerpt any length of this web site and distribute it freely to whomever you choose provided it is for non-profit purposes only. You should identify the source as Website: http://members.aol.com/eyeknowwhy/ Site Title: I Know Why Refractive Surgeons Wear Glasses. Reproducing any part of this site for profit requires specific permission - email to eyeknowwhy@aol.com.

What This Site Does Not Extensively Cover At This Time

This site does not discuss the following extensively at this time:

• Finding a 'good' ophthalmologist or optometrist.
  There are many sites and books on the subject (People's Medical Society is a good source and is a consumer health advocacy group.)
  
• Regulatory agencies of Canada, England, France, Japan or other countries.
  
• Ophthalmologists/Optometrists for Patients with Very Poor Outcomes.
  
• Eye Exercises or Orthokeratology (Cornea Remodeling Using Contacts) to correct nearsightedness.
  

Who is EyeKnowWhy?

EyeKnowWhy is a consumer health site created to present a more accurate picture of refractive surgery. We are not ophthalmologists or optometrists or sponsored or paid by them. We are a group of concerned citizens speaking out based on our research. You can consider this site questionable and go on your way or read it and assess its validity yourself. We do know individuals who have had refractive surgery, some with excellent outcomes and some with devastating outcomes.

EyeKnowWhy bases this site on extensive research, much of it unavailable on the web. EyeKnowWhy recommends you do your own research and form your own opinions. There's nothing for sale here! No agenda to stop refractive surgery. Refractive surgery is a 'miracle' for many people, but not everyone. Be suspicious of everyone - EyeKnowWhy and prestigious surgeons and acclaimed refractive surgery researchers included. That's the way a free market, free speech, caveat emptor ('buyer beware') democratic society works. If you have already had refractive surgery, THINK NOW before you go further - Do I want to know more? This site is graphic and presents issues that may disturb postoperative patients. If not, exit this web site now.

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What Is Refractive Surgery?

Refractive surgery refers to a range of surgical procedures using knives, lasers, or some combination to wound and alter the cornea resulting in structural changes in the cornea's curvature. The resultant change in the cornea's shape often produces a significant change in its refractive power (and thus the eye's visual perception) that may be perceived as desirable by many patients. Damaging the cornea structure creates an array of vision and ocular side effects, some temporary and some permanent. The results of refractive surgery are irreversible and controversial and should only be considered after thorough research.

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Assessing Information Sources

How do you get accurate and unbiased information about refractive surgery procedures like PRK and LASIK? Everybody has an agenda. Who do you believe? Is anything you see, hear or read believable or accurate? Your sources for information about refractive surgery are advertisements and 'patient information' literature from refractive surgery clinics, discussions with people who have undergone refractive surgery (known as postops), consumer books on refractive surgery, web sites with varying agendas, believability and depth, web 'vision discussion' newsgroups, discussions with your optometrists, 'PRK and LASIK vision correction education seminars', ophthalmology trade journals and magazines, medical associations, ophthalmology medical journals of varying quality, TV news and magazine shows and lay press (magazines and newspaper) articles on refractive surgery. All (including this site) should be reviewed with healthy skepticism. EyeKnowWhy provides an extended discussion of Refractive Surgery Information Sources - Extended Discussion and is recommended for first time visitors.

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The Eye Structure - Overview and Links

The eye is a complex structure, and EyeKnowWhy recommends you visit other sites (and especially your public library) to get a general overview of the eye's structure, myopia, hyperopia, astigmatism, and presbyopia. There are hundreds of eye sites that discuss (with variable depth and accuracy) the eye and refractive disorders. Most of the web sites lack depth but they are a start. You can use any search engine and keywords like "Photorefractive Keratectomy", "PRK", "LASIK", or "informed consent", or any combination. Some miscellaneous web sites of note are listed toward the end of this document (see site highlights).

The American Academy of Ophthalmology is one of numerous web sites you should visit before continuing further.

American Academy of Ophthalmology - Refractive Surgery
http://www.eyenet.org/public/ref_surg/ref_surg.html

American Academy of Ophthalmology - Home Page
http://www.eyenet.org/aao_index.html

Some sites provide a comprehensive set of ophthalmology listings. Check out Eye Resources on the Net for their link list.

As mentioned at Eyenet and other sites and the books obtained from your library, light goes through six optical mediums before the image is processed by the brain.

They are:

• Cornea - provides 70% of the refractive power of the eye
• Aqueous Humor - fluid filled area between the cornea and lens. This area is known as the Anterior Chamber.
• Lens - behind the iris, flexible (at least until middle age) and can fine focus up to 2 diopters (possibly more) of farsightedness.
• Vitreous Humor - very thick gel like fluid in main cavity of the eye
• Retina - light processing membrane; converts light into electrical impulses that are transmitted to the optical nerve
• Optic Nerve- millions of optical nerve fibers merge into the 'optical nerve', and terminate in the brain where images are created.

Sight is extremely complex, and all parts of the eye must operate optimally to provide the best possible vision. Unfortunately, the eye is so complex, that slight variations can cause unusual and disturbing vision problems. The most common problems are the refractive errors nearsightedness, farsightedness, and astigmatism and are generally correctable by glasses or contacts. Correction with eyeglasses or contacts may not be easily accomplished in severe myopia, hyperopia and astigmatism. Refractive errors are defined using a measurement called diopters.

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The Diopters

Refractive errors are measured in diopters. The range is between +15 and 0 (hyperopic) and 0 and -25 (myopic), with the range +6 to -6 being by far the most common subset encompassing over 96% of refractive errors. Plus (+) diopters (for correcting hyperopia) indicate a convex lens (bows outward) is needed in eyeglasses or contacts to 'increase the bend' of light rays before they enter the eye. As you recall from the above sites, in hyperopic eyes, the focused image is 'beyond' the retina. The convex lens bends the light so that the cornea and lens can successfully focus the image on the retina.

Important

Many hyperopic (farsighted) people with refractive errors between +.25 and +2 (less so at +2) can use accommodation to achieve good focus without using glasses. However, this 'mild overcorrecting' results in an early form of presbyopia called 'premature presbyopia'. See presbyopia below. Any + prescription above +2 generally means the hyperope needs glasses for far and near vision, i.e., the glasses make them equivalent to an emmetrope.

A diopter of 0 indicates no refractive error, and is called plano.

The minus (-) diopters (for correcting myopia) indicate a concave lens (bows inward) is needed in eyeglasses or contacts to 'decrease the bend' of inbound light rays before they enter the eye. In this case, the image without correction reaches 'focus' in front of the retina. By the time it reaches the retina, it is out of focus to some degree. The concave lens 'reduces the bend' of the light so that the cornea and lens can successfully focus the image on the retina.

Astigmatism is another refractive error and is fairly common with myopes (about 20% of myopes have some degree of correctable regular astigmatism). Unlike myopia or hyperopia, that is rarely caused by a cornea that is "too steep" (a favorite marketing statement by refractive surgeons) or "too flat" (note: it is almost always an elongated or shortened eye ball), astigmatism is almost always caused by cornea irregularity. Regular astigmatism is measured in diopters and cylinder meridian or axis. As mentioned at the beginning of this site, astigmatism will not be discussed extensively. Astigmatism, unless above 2 diopters, is not a major problem during the day when the pupil is smallest. Astigmatism, depending on its severity, may affect daytime vision, but it always affects low light and night vision, sometimes severely. Astigmatism is defined across a meridian or axis. If the cornea was mapped into wedges, two opposing wedges would be a meridian. Regular astigmatism is often described as having a 'bowtie' appearance on color topography maps.

For example, an eye with the following refraction "-3, sphere" has a mild myopic error of -3 and no astigmatism; an eye with the following refraction "-4, +1.5, 180" has a myopic error of -4 with an astigmatic error of +1.5 in the 180 degree meridian (180 degrees is straight across (horizontal) the eye). To understand astigmatism and refractive prescriptions fully requires a lengthy explanation. The major public libraries have two books that provide good discussions of astigmatism, diopters and prescriptions. A good layman's discussion of astigmatism can be found in As I See It by Raymond Munna. A much more extensive discussion can be found in Eye and Its Disorders by Trevor-Roper and Curran. There are numerous other books at the library - get out from in front of the monitor!

Astigmatism below 1 diopter (+ or -) is generally considered a minor vision problem and easily corrected. It is important to understand the difference between regular and irregular astigmatism. Whereas regular astigmatism can be corrected (to a major extent) by corrective lenses and contacts, irregular astigmatism cannot be effectively corrected. Irregular astigmatism can take on all kinds of unusual surface curvatures (especially after refractive surgery). In some cases, irregular astigmatism can be improved (but not corrected) by substituting a 'best fit' regular astigmatism cylinder correction. Irregular astigmatism is a common (and sometimes severe) optical problem after cornea injury or cornea surgery (such as RK, PRK or LASIK). The effect of irregular astigmatism is most prevalent when the pupil is fully dilated, or looking at sharp contrast objects under low to medium lighting (like reading or watching movies at a movie theater). It is discussed further in the Complications of Refractive Surgery section.

EyeKnowWhy has grouped the diopter ranges and their characteristics into the following table.

Table Caveats: All ranges and descriptions are approximate.

Click here for MORE discussion within this topic (Refractive Errors). After reading the extended discussion, use your browser back key to return here.

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The Cornea - A Detailed Look at Its Tissue Structure

The cornea is far more than meets the eye. It is a complex structure with a multitude of functions and extraordinary complexity. Considering its transparency, absence of blood vessels, and ability to withstand the insults of modern life from smoke, fumes, cosmetics, opportunistic organisms and active lifestyles, its ability to maintain its transparency for the entire life of an individual is remarkable. Nevertheless, it is subject to transparency threatening complications. The most serious of these is infections by viruses, bacteria or fungus (organisms) and trauma, accidental or intentional.

Click here for MORE discussion within this topic (Cornea Tissue). After reading the extended discussion, use your browser back key to return here.

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Clarifying Important Concepts

General concepts related to vision and surgery are often misunderstood by the public.

• Surgery

  Surgery is mutilation of living tissue and all surgery is invasive. It doesn't matter whether it is done with a knife or laser. Any surgery that injures any organ of the body presents risks. 'Functional' surgery is surgery intended to interrupt, stop or slow the pathology of a disease. It is 'functional' when removal of a mature cataract is performed in an attempt to restore vision since substantially all vision has been lost because of the cataract; likewise burning and cauterizing a retinal tear with a laser to prevent blindness is functional.

  Surgery that is cosmetic is intended to alter the physical appearance or external feature of the body. A 'plastic' surgery procedure is either cosmetic or functional depending on the circumstances. If the procedure is intended to correct a gross disfigurement, it is functional, ex., a nose job to repair a nose that has been severely damaged in a car wreck. If a nose job is done to alter a large nose that is aesthetically displeasing to the individual, it is cosmetic.

  Surgeries that are elective are considered non-emergent, i.e., there is no immediate need to have the surgery. This does not mean that the surgery is not necessary to avert adverse consequences. Many elective surgeries could be considered 'medically necessary' for this reason. However, 'medically unnecessary' elective surgeries must be considered by the prospective patient in the context of their possible risks and benefits, and should always have a very high benefit and very low degree of risk.

  So where does refractive surgery fit? Well, it's definitely elective and medically unnecessary since glasses and contacts are effective alternative solutions to refractive errors in 'almost' all cases. So is it cosmetic or functional? In most cases, refractive surgery does not alter the physical appearance of the eye enough. Cornea scars and iris pigmentation loss are not easily observable with the naked eye and would not be considered advantageous if they were.

  Is it functional in those patients that no longer need glasses for a period of time? Is it functional in those patients who do not need glasses as much as before the surgery? Is it functional in the severely myopic or astigmatic patient that has an excellent outcome? Many would argue it is. You have to decide for yourself.

• "Persistence of Vision"

  The eye is a remarkable structure. It 'wants to see', and can withstand a remarkable amount of trauma, and continue to do so to some extent. Anyone who reads journals detailing cornea transplant, cataract surgery or refractive surgery would be amazed that the eye is able to survive such invasive surgery. But it does. Many people have difficulty reconciling damaging the cornea and visual improvement. How can wounding and scarring the cornea result in vision improvement? Yet, the initial effect after refractive surgery does improve many aspects of vision in most cases, but it does come at a price to other aspects of vision, and the risk of short term and long term complications.

• Loss of Visual Acuity and Blindness

  Blindness takes on many meanings depending on the clinical and personal perspective. But what is blindness exactly? To some percentage of the population, it would be anything less than vision correctable close to 'perfect' vision. But this is not 'blindness' but may be considered a loss of visual acuity. Some people believe best correctable vision less than Snellen 20/40 (i.e. the person can read the 20/40 line, albeit slowly, with glasses) would be blindness. It is a loss of visual acuity. The government's definition of legal blindness is when the best eye of an individual cannot be corrected by glasses or contacts to read the 20/200 (big "E") on a Snellen eye chart. EyeKnowWhy considers a person 'blind in one eye' when that individual cannot read the 20/200 line with glasses in any eye. There are other more extreme degrees of blindness. CF stands for counting fingers only (at close range), LP stands for light perception, and NLP (or absolute blindness) is no light perception.
  

  EyeKnowWhy defines "functional blindness" after refractive surgery where the vision acuity in one or both eyes is worse than 20/40 best corrected with glasses and suffers moderate to severe optical aberrations and non-visual ocular disease symptoms. This is EyeKnowWhy's definition. You have to decide what your definition of functional blindness is.

• "Safe" and "Effective"

  What does 'safe' and 'effective' mean? For that matter, what does 'proven' or 'conclusive' mean? The definitions are as varied as the agendas of those providing the definitions. Generally, a procedure proven 'safe' represents little or no risk of permanent damage or injury, either in the short term or long term view. A procedure proven 'effective' should provide expected results consistently and that are patent, i.e., permanent. All refractive surgery procedures do not meet these high qualifications. This is true of all surgeries because all surgeries have risks. The issue then becomes how much risk of permanent harm is acceptable in an elective surgery. The definition of acceptable risk is difficult, and is dependent on perspective, i.e. one person or group's definition may vary considerably from another person or group. For example, the FDA PRK studies showed 7% of Summit patients lost 1 or more Snellen lines at the 1 year point (best corrected vision with glasses). Is this 'safe' and 'acceptable' risk? It was for the FDA's ophthalmic advisory review panel and for the FDA regulatory staff. You should be aware that the FDA uses the term 'reasonable safety and effectiveness'. Furthermore, how long a follow-up does a procedure require before it is considered 'safe'? Since many people who have refractive surgery are in their 20's or 30's, is a 2 year follow-up in the clinical trials long enough? Is 5 years? Is 10 years?

  There is no doubt that many refractive surgery patients experience a permanent reduction in quality of vision, especially at night, compared to their pre-operative vision corrected with glasses or contacts. In a few cases, moderate to severe vision impairment (including blindness) will occur. There are also cases where patients' visual acuity improved after refractive surgery; for example, patients with high myopia and severe astigmatism may actually have considerable improvement in their uncorrected and best corrected vision (assuming they do not develop other complications such as irregular astigmatism or significant scarring, and heal as expected). It is also recognized that the long term effects of all refractive surgery procedures are unknown.

  It is true that 80% to 96% (depending on which study you review) of post operative patients have enough acuity (based on a Snellen eye test) that they do not have to wear glasses except for certain tasks such as reading or driving at night. It is also true that the overwhelming majority of patients are happy with their results 12 months after surgery (based on the most recent studies of patient satisfaction). But this claim of 'success' and 'satisfaction' must be inspected closely. Most studies are only short term snapshots in the lives of postoperative patients (6 mos. 1 year, 2 year, 3 year). A patient who needs glasses after surgery will discover that glasses do not correct many optical aberrations and ocular symptoms that are persistent and common after surgery, and that the prescription may be small but unusual. Cornea distortion and scar irritation may make contact lens wear impossible. What's more, cornea wound modeling in the years after surgery may result in a more frequent need for new eyeglass prescriptions as the cornea 'remodels' and the acuity changes.

  Much of the argument about the safety of refractive surgery is based solely on the Snellen eye chart test, a limited test of visual acuity, that does not test many visual functions such as symmetry of acuity between the two eyes, contrast sensitivity (high and low, with and without glare sources), astigmatism (regular and irregular), cornea clarity, masked mild hyperopia, glare, optical aberrations` and night vision. You need to understand these concepts before making an informed decision.

• Optical Zones and Optical Axis

  Any discussion of refractive surgery requires an understanding of optical zones. Optical axis refers to the central axis of the cornea, pupil, and lens. Optical zones refer to various zones of the cornea that are the primary (i.e. greater than 90%) passthrough points for light projected on the retina. The central optical zone is where the light that provides detail and color passes through. During the day when the pupil is small (sometimes very small), over 90% of the light processed by the retina passes through the central optical zone. What is the diameter of the central optical zone? There appears to be no specific rule but three to four millimeters is the approximate range. Remember, the cornea's diameter is between 11 and 13 millimeters. The next zone is called by various names, so EyeKnowWhy calls it the Mid zone. The diameter is variously defined between five and seven millimeters. Under moderate to moderately low light, the Mid zone comes into use to pass 90% of reflected and direct light. Myopia PRK is currently done with a 6mm (most common), 6.6mm and a 7mm ablation/transition zone. The Peripheral zone comes into play for low light conditions (such as driving in areas with few overhead lights). The defined diameter varies with pupil size; ranges are between 7 and 10 millimeters (or about 2 millimeters more than the pupil diameter under low light conditions). It is important to understand zones (and the diameter of your own dilated pupil) because scar formation and ablation wound profiles fit within these zones, and thus create optical aberrations such as glare, starbursts and halos of varying intensity dependent on the 'zone' used for the laser ablation or knife cutting.

  Since refractive surgery alters the curvature of the cornea, and thus its refractive powers, the cornea's focusing power and characteristics change as the pupil dilates and inbound light rays are refracted differently from the central ablation zone, the transition zone and the untouched peripheral area. After refractive surgery, three zones of different refractive power are present: The central optical zone is where the full ablation occurs and has the greatest decrease in diopter power; this zone is usually between 4mm and 6mm in diameter. The transition zone encircles the central optical zone, and receives a 'transition ablation' that decreases from the inside edge to the outside edge that meets the untouched peripheral part of the cornea. The transition zone is 1mm to 2mm wide ring. The combined ablation zone (central plus transition) is 5mm to 7mm. Newer techniques may be larger and go up to 9mm total (usually only for hyperopic corrections). These changes in refractive power and its effect on the 'sharpness' of the image often encompass abstract terms such as contrast sensitivity, reduced night driving vision, increased GASH, night glare, multifocal lens effect (ghosts and double images) and the 'veil' effect that light scattering has on the retinal image.

  For a more extended discussion, a separate page Refractive Surgery's Effects on Retinal Image and Contrast Sensitivity -under construction is available if you would like to know more.

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Assessing Refractive Errors and Snellen Visual Acuity Testing.

Post operative patients are always saying 'I see 20/15 with my left eye, and 20/25 with my right eye' or 'I'm 20/20 now.' or 'I can see 20/30 without glasses.', 'Night vision isn't that much of a problem.', 'Glare and halos are only occasionally noticeable.', or 'I only need to wear glasses to drive at night.' Just what does all this mean?

Everyone is familiar with a Snellen eyechart, big 'E' at the top, and lines of letters decreasing in size. A person who can 'read' the 20/20 line is said to have '20/20 vision'. But is that misleading? It depends.

Do you remember the testing that occurred at your last eye exam? One or two? Two or three? During that process, the examiner is fine tuning your spherical (myopic or hyperopic) and cylinder (astigmatism) lens power for best corrected vision. You may also recall eyedrops to paralyze the lens and prevent accommodation from masking mild hyperopia. During the last part of the process, you are still reading the same '20/20' line; they are just making it sharp! Other tests are done to evaluate your contrast sensitivity in normal and low light conditions, peripheral vision, retina health, cornea health, pupil dilation, and other eye functions. The point is, that Snellen, although commonly used as the 'standard' for visual acuity, can be misleading.

The term 20/20 DOES NOT MEAN EMMETROPIA (i.e plano or zero correction needed) or exceptional quality of vision or peak function of vision or excellent night vision or excellent contrast sensitivity or absence of glare or visual distortion or regular astigmatism or irregular astigmatism or early cataract formation or a host of other things such as abnormal tearing, eye pain, glaucoma, eye throb, headaches, and equality of visual acuity between the two eyes. Those are discerned by other tests and in many cases rely on patient subjectivity and must be assessed separately. However in normal unscarred myopic eyes with mild to moderate myopia and mild to moderate astigmatism, these other assessments are normal or very close to normal when corrected by eyeglasses or contacts.

It is possible (and often likely) that people who have refractive surgery can have several of the above other factors be mildly or significantly worse than before surgery and be able to 'read' the 20/20 line. For example, the cornea to the left has undergone RK resulting in significant scarring, but the uncorrected visual acuity is 20/30 (based on Snellen line read). Whether this patient is happy is subjective, and whether that happiness will last is undetermined.

EyeKnowWhy located two trade magazine articles online that discuss patient satisfaction after PRK (note these surveys had a very low return rate for questionnaires):
EuroTimes - 1994, (patient satisfaction; some what old but enlightening)
http://www.escrs.ie/eurotime/
UPDATE: Sorry, this article is no longer available to the public - now membership only protected. This article showed about 75% of patients were satisfied after two years. Many patients complained about night vision effects, and ghost vision.
Eyeworld - Patient Survey Shows High PRK Satisfaction - Feature Article http://www.eyeworld.org/March/patientsurvey61.html.html {UPDATE: Sorry, this article is no longer available to the public - now membership only protected. Basically it said that one year after PRK 85% are happy and 15% are unhappy. Patients report persistent night vision problems.

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Refractive Surgery, Decreased Visual Acuity, and the Risk of Blindness

The picture to the left is a clear unaltered cornea. Refractive surgery does damage, scar and distort the cornea structure, but very rarely results in blindness. This has been shown throughout the ophthalmology journals. There are pictures of corneas that have undergone numerous procedures, developed severe scarring and irregular astigmatism, but the eye is not blind. Amazingly, some of the eyes (using the scarred and distorted cornea pictured in the journal study) actually have uncorrected visual acuity of 20/40 or better (remember the limitations of Snellen testing).

"Corneal Scars are the inevitable sequel to any injury of the cornea that transgresses Bowman's membrane. The extent of such scars necessarily depends on the extent of the injury to the cornea lamellae [i.e., tissue layers] and the vehemence of any superadded infection; the amount of clearance of such scars is dependent on the youth of the patient, becoming proportionately less as age advances.

Scars are termed nebulas if they are translucent 'cloudlets', and leucomas if they are dense and 'white'. The degree of visual impairment depends partly on the position of the scar (axial opacities causing gross visual loss and peripheral opacities none), and partly on the density of the scar - the slighter 'nebulas' causing, paradoxically, more confusion than the opaque leucomas, since the former allow distorted light rays to reach the retina, giving vicarious stimulation, while the totally opaque leucoma merely reduces the number of entrant rays." From Eye and Its Disorders, Trevor-Roper and Curran, 2nd Ed., P. 379

The good news is that cornea scars (or severe cornea haze) do diminish (albeit slowly) in the majority of eyes in the years following cornea surgery.

Vision Threatening Complications and Risk of Vision Impairment

Although corneas that are damaged or scarred by refractive surgery can perform, and even perform well, all prospective patients should be aware that vision threatening complications may occur after surgery (immediately or delayed for months or years). There are six critical complications that may occur after refractive surgeon (or in natural aging or accidental eye trauma) that can lead to legal blindness or absolute blindness in the affected eye: uncontrolled infection, cornea ulceration, cornea rupture, cataract, retinal hemorrhage, detachment and failure, and optic nerve atrophy/disease.

Vision impairment is more difficult to define. It is not just an inability to read the same Snellen line with glasses after surgery as you could with glasses before surgery.

Vision threatening complications and an assessment of vision impairment with examples are provided in the extended discussion page Vision Threatening Complications and Vision Impairment Examples.

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How the Cornea Heals

Because the cornea is avascular (without blood vessels), all cornea wounds of any substantial size heal slowly over many years. This prolonged period is called cornea wound remodeling. However, EyeKnowWhy divides corneal wound healing into four stages. The four stages after wound trauma that penetrates Bowman's Membrane are a)initial barrier restoral and epithelial infill, b) cornea recovery and wound healing initiation, c) scar formation, and finally, d) long term cornea wound remodeling. All cornea wounds that penetrate Bowman's Membrane heal by scar formation. For each type of refractive surgery (Radial Keratotomy - RK, Photorefractive Keratectomy - PRK, and Laser Assisted In-Situ Keratomeuliesis - LASIK), these stages have slightly different characteristics.

Click here for MORE discussion within this topic (Cornea Healing). After reading the extended discussion, use your browser back key to return here.

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Patient Happiness and Unhappiness

What makes a postop happy or unhappy? It depends on a number of things. Results, expectations, and time since surgery all play a major role in a postop's happiness or unhappiness. Patients who have poor results or 'significant' complications are obviously unhappy. People who like 'things just right' should avoid refractive surgery. People who are bothered by persistent 'visual quirks' (e.g., glare, halos, transient wakeup edema, reduced night vision) after refractive surgery should avoid it entirely. For example, it is quite possible for a person who had an excellent outcome in relation to most postops will be unhappy because of mild side effects. A 'finicky' patient with an excellent outcome may dislike seeing halos and be very dissatisfied. A person with severe myopia or astigmatism may be happy with improvements that would be very unsatisfactory for a mild or moderate myope. You also have to look at happiness over the very long term. A person in their 30's who is mildly overcorrected may be upset when he needs reading glasses to read or do close work in his early 40's. Also, if a person regresses or progresses or develops a 'significant' complication five, ten or twenty years after surgery, they may become unhappy then. Surveys show about 90% to 96% of patients are happy (or satisfied) at the end of year one, but these surveys are sometimes questionable due to nonresponse, and the subjective nature of the questionnaire. It just "depends". Remember, every minute you are awake and for the rest of your life, you will 'see' the results and side effects, if any, of refractive surgery.

Click here for MORE discussion within this topic (Patient Happiness/Unhappiness). After reading the extended discussion, use your browser back key to return here.

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The FDA

The FDA is supposed to protect and serve the public but that is not how it always works. Of all the regulatory agencies in the world responsible for protecting that country's citizens from health fraud and unsafe drugs and medical devices, it is generally considered the best.

The History of the FDA

Prior to the FDA's establishment by Congress, Americans were often the victims of health care fraud and dangerous drugs and medical devices. Originally chartered to regulate drugs and food, in 1976 Congress expanded the FDA's authority to include medical devices. Medical devices prior to 1976 were 'grandfathered'. After 1976, medical devices were assigned classes; Class I devices present the least risk, Class II are a step up, and Class III present the greatest risk to patients. All new medical devices are classified, and in some cases a device could bypass almost all regulatory review by obtaining a 'substantial equivalency' designation. Substantial equivalency is somewhat controversial but will not be discussed further here. As the FDA has matured, and its critical importance to the welfare of the U.S. population (as well as drug and medical device manufacturers bottom line) has become recognized, it has come under fire on all sides. Consumer health advocates argue that reviews are flawed, and 'safety and effectiveness' standards are too low. Manufacturers argue the review process is too complex, too lengthy, and standards and review costs too high. Some things the FDA does well. There are many drugs and medical devices that never make it to market and harm thousands, if not millions of people, because of problems uncovered by FDA review. But there are perceived failures. For example, the Dalkon shield and breast implants, Fen/Phen (still controversial) and Olestra (fake fat). Like any agency that decides the fate of products with billions (that's billions) of dollars in potential revenue at stake, it also is subject to intense lobbying. Lobbying can be direct or indirect. Drug and device manufacturers do not give money to politicians without cause. Likewise, the indirect lobbying is even more invisible. Regulatory coordinators for manufacturers may have too cozy of a relationship with FDA staff. Medical 'associations' may pressure the FDA to approve products. FDA review panels may be dominated by physicians with conflicts of interests. FDA staff may consider job opportunities with manufacturers after leaving the FDA in their review decisions.

Because of the above and other possible conflicts, any FDA approval of a drug or medical device must be considered with some skepticism and understanding of what 'reasonable safety and effectiveness' means. Do not rely on any regulatory agency to protect you from unethical, incompetent doctors or surgeons, or questionable medical treatments and surgical procedures.

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The History of Refractive Surgery - Through Radial Keratotomy

As early as the 19th century there were observations that some individuals who experienced cornea injury experienced significant changes in visual acuity. In very rare events, nearsighted trauma victims may experience a dramatic decrease in their nearsightedness. It was also observed that these positive changes in visual acuity were often accompanied by a wide array of visual aberrations and ocular disease symptoms associated with trauma to the cornea and eye. Not much was thought of it.

In the early 1950's, a Japanese eye surgeon, Dr. Sato began experimenting with placing primitive cuts in the corneas of volunteer myopes. These cuts were around the outermost part of the cornea, were numerous, and completed with a scalpel that often penetrated into the chamber. Occasionally, the resulting scarred and deformed cornea did somewhat improve vision, but complications were common and severe. Sato eventually abandoned this early form of radial keratotomy, but only after operating on thousands of corneas. The long term results of Sato's surgery are well known - almost all of his 'volunteers' are now blind as documented in the Contact Lens Association of Ophthalmology Journal and the American Journal of Ophthalmology articles (CLAO J, "Problems arising from Sato's radial keratotomy procedure in Japan", Akiyama K., Tanaka M., Kanai A., Nakajima A., Vol. 10 P 179, 1984; Am. Jrnl. Ophthalmology,, "30 year follow-up of posterior radial keratotomy", Beatty R.F., Smith R.E., Vol. 103, P. 330, 1987.) These are not available online.

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'Modern' Radial Keratotomy Is Born

Around 1973, a Russian eye surgeon named Vyataslov Fyodorov experimented with Sato's incision technique, and 'modern' Radial Keratotomy (RK) was born. There has been a legend associated with Fyodorov's RK involving a patient of Fyodorov's RK. As the story goes, this patient came to Fyodorov with glass fragments (in his cornea(s)). Dr. Fyodorov removed the fragments (which supposedly had not penetrated the anterior chamber (the liquid filled void just behind the cornea and before the iris/lens complex). Rather than suturing the lacerations, Fyodorov allowed them to remain gaped open and heal by scar infill. After experimenting on rabbits and other animals for a few years, Fyodorov began experimenting on human corneas. Claims of tremendous 'success' were met with skepticism. Nevertheless, 'pioneering' U.S. eye surgeons trekked to Russia, and learned Fyodorov's Russian RK technique. Radial Keratotomy was introduced to the U.S. in 1978 by these 'pioneers'. Fyodorov went on to invent "assembly line RK" surgery at his clinic in Russia. In this 'factory', patients are placed on gurneys that are on automated tracks. By moving through a procedure 'factory', RK is broken down into individual processes and large numbers of patients can be done during a day. There is an amazing picture of this process in the National Geographic, Nov. 1992 issue ("The Sense of Sight") (Click Here to see Fyodorov's Assembly Line RK Factory), and a witty interview with Fyodorov and a site visit to the surgical suite in his Moscow clinic in Health, Nov./Dec. 1993 "Sight for Four Eyes" by Mary Roach.

Because RK uses only a knife in the surgical process, there is no oversight or regulatory review requirement, government or peer. This is important to understand because it explains how the wide scale marketing of keratotomy ('cut the cornea') procedures in the U.S came about. No government regulation or review means anyone with a medical degree of some type and a scalpel can perform RK or any other refractive surgery procedure such as ALK, AK, HK (Hexagonal Keratotomy), using only a knife and common eyecare instruments with no or minimal training - all it takes is a patient willing to sign a consent form. Up until 1982, there was no credible large scale, long term study of the safety and effectiveness of RK. During 1982, the National Eye Institute, a division of the U.S. National Institute of Health, under the directorship of Dr. Carl Kupfer, funded a multicenter, multiyear study of RK. A coalition of refractive surgeons under the leadership of Dr. George Waring, Emory University, began the study with the well recognized name PERK for Prospective Evaluation of Radial Keratotomy. Besides reporting summaries of PERK outcomes, many specialized substudies of RK surgery effects in the PERK 'volunteers' have been published. These 'substudies' and the PERK summaries have been published in peer reviewed ophthalmology journals. In reviewing any refractive surgery study and its conclusions, please keep in mind potential conflicts of interest by its authors and the credibility of their conclusions.

The PERK study enrolled 435 patients in 1983 and 1984. Of these, 792 eyes were operated on. This represents approximately 80% of the PERK study group that had both corneas surgically altered, and 20% who declined surgery on the second eye. For safety reasons (in case of disastrous complications such as infections and retinal detachments), patients had to wait at least 1 year before having the second eye done (note: a few did not). One of the questions you may ask is "If RK is so 'bad', why did 80% choose to have the second eye done? Patient reasons vary - some had a 'good' outcome with the first eye, and wanted to do the second. Others had difficulty with anisometropia (refractive mismatch between the two eyes) and believed it would be better to try and bring the acuity of the second eye more in line with the first. Others were unhappy with the first and refused surgery on the second eye. Patients' decision to have the second eye operated on is complex and in some cases illogical. Complications of keratotomy surgery are well known and well documented in the ophthalmology journals.


To the left is a typical 12 cut RK done in 1995. You can clearly see the debilitating scarring that resulted. In this patient, the uncorrected visual acuity was 20/30 - 20/40 after surgery (based on their ability to discern letters on a Snellen eye chart), but vision quality was debilitating. This patient is not happy though they are considered a "clinical success."

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The History of Refractive Surgery - Today's Laser Surgery

In 1983, it was postulated that the excimer laser may be viable in modifying the cornea structure. Two companies eventually emerged to pursue development of excimer laser surgery on the cornea, Visx and Summit. Initial designs were to use the excimer laser to make the RK cuts rather than a knife. This didn't work well and was abandoned. The alternative technique was to reshape the central and mid optical zone of the cornea by using a diaphragm (mechanical iris) to create a flattening of the central cornea. By 1988, Visx and Summit applied and received Investigational Device Exemptions (IDEs) from the FDA.

Photorefractive Keratectomy - Details and Analysis

You can visit numerous web sites to get an idea of the overall clinical procedure and preparation. This site focuses on the physical details of PRK during the procedure, and the wound healing that occurs during the initial year. With PRK, wound creation is done in the central optical axis and the peripheral area is left untouched. Three of the recognized difficulties of the PRK procedure is stripping the epithelium, centering of the ablation wound and consistent ablation as tissue removal progresses. Once the patient has been trained to focus on the light and the eye has been anesthetized, the epithelium must be removed. This is quite traumatic to the cornea as you can well imagine. Current techniques are scraping with a spatula blade, dissolving with chemicals or ablation with a few pulses of the laser. After removing the epithelium, the laser is then fired successively building a crater shaped wound as Bowman's Membrane and part of the underlying stroma is ablated. PRK achieves tissue destruction by pulsing on and off UV laser exposures. Each laser pulse is rapidly absorbed by the cornea tissue. The internal water of the cornea surface cells rapidly boils, vaporizes and expands, exploding the cell walls. This is a picture taken with extreme magnification showing the 'plume' of tissue debris being ejected from the cornea surface after a pulse of laser light. One of the problems that plagues PRK is uneven stroma removal resulting in elevated spots of stroma tissue in the central optical zone (central islands), or in some cases, excessive tissue removal spots (keyholes,pits). The causes are complex, and relate to fluid movement from exploded cells between UV exposures inhibiting ablation during subsequent pulses, and difficulty in managing consistent laser energy across the diameter of the beam thoughout the ablation process.. Another problem is transitioning from the ablation wound to the unablated cornea tissue. Off center wound profiles are a problem and relate to poor initial alignment (with the central optical axis), patient focus drift (not keeping their eye on the 'little light'), and saccadic (involuntary) eye movement. Did you know your eye is always moving even when you are staring? It's small and involuntary, and is called saccadic eye movement.

PRK to correct myopia involves removing tissue from the central and mid cornea. The reduction in refractive power is achieved by removing more tissue from the center of the cornea than from the midzone cornea. This results in a reduction of the refraction or bending of the rays passing through the ablated parts of the cornea, and thus moves the image farther back toward the retina. Overcorrection occurs when the changed curvature is too great, moving the image 'beyond' the retina resulting in farsightedness. Astigmatism is 'corrected' by cutting away a pie shaped section of the cornea along the angle of the cornea's steeper sections. Farsightedness is corrected by cutting a circular 'trench' called an annullus along the midzone of the cornea, and progressively carving less tissue at the center of the cornea. The annulus is usually created at a diameter of six or more millimeters to reduce night vision aberrations which can be severe. Newer farsighted techniques moves this annulus out to seven or eight millimeters. The resulting effect is a steepened 'hill' in the central zone. Because a farsighted 'sculping' is more irregular than a myopia 'flattening', it is more difficult to create, and the cornea's physiology does not 'seem to like' the steepened central zone. A stroma and epithelial fillin response occurs causing significant regression. The peripheral annulus tends to produce a more profound scarring response as well. Currently, only myopia and astigmatism have been approved by the FDA. Astigmatism ablations tend to cause a stronger wound response, and more optical side effects such as irregular astigmatism, glare, halos, arcs, and starbursts.

The picture to the left is a scanning electron microscope (SEM) photo immediately after PRK myopia ablation, and reflects the smooth 'cutting' of cornea tissue by the excimer laser. The central zone (3) is fully ablated, and a transition zone (2) merges into the epithelium (1). Newer excimer lasers and scanning lasers supposedly provide a smoother transition zone than that shown here. The epithelium within the ablation zone is removed prior to ablation.

The ablation technique for myopic, astigmatism and hyperopia for LASIK is the same as PRK, except it is done on the stroma exposed after the flap is lifted out of the way. One notable difference is that the ablation depth for LASIK may be adjusted compared to that for PRK, since a PRK ablation may include extra ablation pulses to compensate for stroma regrowth which does not seem to occur after LASIK. In addition, any additiional adjustments for central island prevention may need to be adjusted as well since central island formation may be different for LASIK than PRK for the same attempted correction. This 'fine tuning' is established as experience progresses, and is a very good reason NOT to be the first for a 'new and improved' version of the laser. Let others get these early and easily corrected 'bugs' out.

Epithelial regeneration is a complex problem following PRK. As you may recall, the epithelium is normally 6 cell layers thick, and the lowest layer is known as basal cells. After PRK, there is no Bowman's Membrane remaining within the ablation wound area. Within the first 3 days (sometimes less, sometimes more), a layer one to two cell layers thick of epithelium regenerates from the edge of the ablation wound. This is critical to prevent infection and rapidly reduces eye pain stimulated by the residual nerves in the exposed stroma.

Because Bowman's Membrane is destroyed, a scar wound healing response is evoked after PRK. This scarring that occurs in the ablation wound manifests itself as a haze under the slit lamp. Haze (or scarring) is assessed on a scale of 0 (no haze, clear cornea) to 5 (severe scarring and degradation of vision). Most eyes begin to develop a hazy scar between 1 and 2 months after surgery. Over the next 12 months, this haze does decrease. Despite the PRK scar/haze scale, assessment is still fairly subjective. 'Trace' haze and sometimes the wound edge can be detected in almost all eyes with the appropriate slit lamp angle, lighting and magnification at 12 months. Still, haze graded below 1 (often called 'trace') does not seem to impair vision although it may increase GASH. The picture to the left is a PRK eye at 12 months with grade 2 haze/scarring.

One of the subset studies that was performed within the FDA PRK trials was using PRK after 'failed' RK surgery. The results were poor. In many cases, substantial haze and scarring developed, healing was slower and more problematic than in eyes that had no previous surgery and significant reductions in best spectacle corrected visual acuity (BSCVA) occurred. Despite this, there are refractive surgeons who market PRK to RK patients seeking solutions to their vision problems. If anything, EyeKnowWhy hopes that RK patients do extensive research before attempting PRK or LASIK surgery over a cornea compromised by RK scars. The photo to the left is a cornea that developed substantial haze after PRK after RK. The white lines are the RK scars.

If anything comes out of your reading this site, it is that RK and AK are bad ideas and should be avoided by everyone. You have to be really wary of any surgeon who defends any type of keratotomy procedure (RK or AK).

Because laser refractive surgery is so financially lucrative, some disturbing trends have occurred. The advent of 'black box' lasers, changes in 'treatment techniques' without adequate clinical research, and the promotion of new surgical procedures such as LASIK without adequate research are increasingly common.

Black box lasers are particularly disturbing. Since these excimer lasers are made without quality controls associated with lasers undergoing FDA trials, the risks to the patient increase significantly. Is the 'power' of the excimer beam calibrated correctly? Does this machine perform consistently? Black box lasers began showing up in 1995, and a few are still in operation today. The following are news stories in the online journals regarding 'black box' lasers:

• Journal of Refractive Surgery (JRS) Sept/Oct. 1995 - Black box laser user responds to editor
  http://www.slackinc.com/eye/jrs/vol115/9let.htm
  
• JRS Sept/Oct. 1995 - Custom Excimer Users Threaten PRK Success
  http://www.slackinc.com/eye/jrs/vol115/news3.htm
  
• JRS Sept./Oct. 1995 - FDA Takes on Maker of "homemade" Excimer
  http://www.slackinc.com/eye/jrs/vol115/news1.htm
  
• JRS Nov./Dec. 1995 FDA Investigates Injury
  http://www.slackinc.com/eye/jrs/vol116/11news1.htm
  
• Ocular Surgery News (OSN) Feb. 1996: FDA's bark may be worse than its bite when it comes to LASIK
  http://www.slackinc.com/EYE/osn/19962a/lasik.htm
  
• OSN June 1996 - FDA loses control of black market excimers http://www.slackinc.com/eye/osn/19966b/black.htm
  
• JRS Nov./Dec. 1996 - FDA Begins to Act Against Unapproved Excimer Lasers
  http://www.slackinc.com/eye/jrs/vol127/news.htm
  
• Eyeworld Dec. 96 - Feat Article FDA Grants Grace Period To BlkBox Laser Owners http://www.eyeworld.org/December/fdagrants.html.html (UPDATE: This article may not be available due to recent membership only restrictions by Eyeworld)
  

Laser Assisted In-situ Keratomileusis (LASIK) - New and Unproven

LASIK is the newest technique promoted for 'vision correction'. LASIK is being marketed as the solution for almost all refractive errors (severe myopia, high astigmatism and hyperopia) and for rapid recovery and 'fast' healing. It was the predominant surgical procedure worldwide by the end of 1997. Still to look at it in detail, it is certainly an 'intense' procedure requiring great skill to get that flap just right. If you haven't reviewed other sites promoting LASIK, do so now.

Some sites you may visit are:

Laser Site (The Vision Correction Website)
Emory Vision Correction Center

The 4 Steps of a LASIK Procedure

LASIK is PRK with a flap of surface tissue that is placed over the ablation wound. This is where great skill, surgical experience and the right keratome (cutting device) are really critical.

When the flap cutting and relaying of the flap over the ablated stroma 'bed' is done, things can go very badly, with devastating results. Some of the known problems are lopsided and decentered cuts, complete detachment resulting in a 'cap', thin caps and flaps, rough flap edge due to blade 'chatter' during cutting, cap/flap wrinkle, epithelium ingrowth, adverse growth of striae (collagen fibrils between bed and flap), caps lost, cap/flap necrosis and 'fall off', cornea ecstasia, central islands and keyholes in the ablated stroma, and irregular astigmatism.

Because the microkeratome is considered a "finicky" machine and subject to failure and inconsistent cuts, new flap cutting techniques using a fine jet of high pressure water to cut the flap are under investigation. Initial clinical trials have shown this to be promising with less shredding of the stroma tissue (compared to the keratome reciprocating blade), improved operational view, and decreased need to pressurize the eye (During the current keratome cut, the eye's internal pressure must be raised to approximatley 65 Hg - an eye's regular pressure is less than 20 hg - to distort and flatten the cornea for the lamellar cut pass of the blade). This "waterjet" cutting device is also being looked at as providing a cleaner and smoother removal of the epithelium for surface PRK as well. Waterjet is expected to be available in 1999. Newer blade microkeratomes with easier operation, transparent head compoents for viewing of the cutting process by the surgeon, and disposable blade assemblies are also in clinical trials. Since these new keratomes and the waterjet will be classified as "substantial equivalent" equipment to older keratomes, FDA approval will be expedited.

Because the flap provides a 'preserved' layer of epithelium and Bowman's Membrane, the immediate (within a week) visual results can be remarkable if done right, and there is a lot that must go right. When it does go right, the results can be dramatic, especially for the severely myopic. Still, this is a major incision across the horizontal plane of the cornea, and the issue of the type of wound healing that occurs between the cap/flap and the stroma bed, as well as the long term viability of the flap are concerns. Is the cell nourishment and hydration of the stroma bed and flap tissue impeded by the horizontal incision? Only time will tell. Many refractive surgeons favor LASIK because it leaves Bowman's Membrane intact over the optical zone, and avoids the problem of the epithelium infrastructure having to rebuild from scratch over a foreign subsurface (the now exposed stroma). Although these are reasonable arguments, the creation of the flap is a considerable risk and the long term viability of the flap beyond a couple of years has not been fully studied. Flap manipulation must be kept to an absolute minimum to prevent epithelium abrasions, "lacquer cracks" in Bowman's due to excessive bending and pressure, and unintentional "tear loose" of the flap at the hinge. Most refractive surgeons believe the flap will remain viable but the actual types of long term flap complications and their frequency will not be known for many years.

LASIK also is considerably less painful than PRK because the epithelium and Bowman's membrane is largely left intact. This assumes a successful and clean "flap creation." Also, enhancements for LASIK are "easier" than PRK because you can relift the flap (for a set period of time) whereas in PRK, the epithelium has to be rescraped and go through the painful and sometimes unpredictable regeneration process. Of course a "bad" LASIK, and especially a "bad" flap, can be a real nightmare.

You should visit the Better Health and Medical Network (AOL only) and review the postings on the Vision board. Some posters have had excellent results and some have had disturbing results.

First Person Experiences There have been articles in two of the ophthalmology trade magazines relating LASIK experiences. They are:

OSN: Patient's third LASIK enhancement procedure - 1st person

My Eye: An Ophthalmologist's First-Person Comparison Of LASIK and RK (Yes, there are a 'few' refractive surgeons who have had surgery themselves.){UPDATE: This article not available due to membership only restrictions. Basically, a refractive surgeon in Atlanta had RK years ago in one eye. Recently, he had LASIK in the other eye.

Other Laser and Non-Laser Refractive Surgery Techniques

Excimer laser technology continues to evolve. There are numerous new excimer laser 'machines' and non-laser techniques that are being tried. New excimer lasers by Lasersight, Chiron, ATC, Novatec, Aesculap-Meditec, and Nidek claim to perform PRK and LASIK ablations more accurately and are claimed to be safer than the current Summit and Visx lasers.

New beam techniques (narrow, scanning, 'flying spot') and eye tracking are in clinical trials. The Summit Omnimed, VISX Star and VISX StarS2 use what is known as a 'broad beam' where the beam is controlled by an iris diaphragm, and expands from the center to the perimeter of the planned ablation wound. The newer lasers (currently in clinical trials in the US, and available unrestricted in other countries) have optical systems that allow the beam size to be controlled in a variety of ways, and move about the ablation area. Small 'scanning beams' such as the 'rectangular slit' of the Nidek and the 'flying spot' of the Autonomous LadarTracking and Chiron Technolas 217 transfer less energy per pulse (due to their small size). Theoretically, controlling the beam movement and overlaying many small ablations result in a smoother and more accurate ablation, and optimal wound transition edge. Likewise, these scanning beams are supposed to provide more accurate astigmatic ablations, and have been recently promoted as capable of hyperopia treatments. They all destroy Bowman's Membrane during PRK wound creation.

There are currently nine excimer laser vendors in production or clinical trials - Autonomous Technologies, Chiron Vision Technolas (217 is the latest model), Kera Technology, Lasersight, Nidek, Novatec Laser Systems, Photon Data, Summit Technology, and Visx, all with varying claims of safety and effectiveness. The Motley Fool stock message boards can be insightful regarding these companies and their marketing strategies and clinical claims. You can also access the Yahoo stock message boards for the publicly traded vendors, as well. Beware, these boards can involve heated debate. Autonomous has a site that discusses their FDA approval and their eye tracking design to reduce decentration, improved ablation wound smoothness and reduction of problems associated with saccadic eye movement. Autonomous was approved by the FDA for myopia and astigmatism in late 1998. Autonomous is currently in a merger agreeement with Summit Technology. Nidek has also been approved for myopia treatment in the US. Other lasers nearing approval include Lasersight and Bausch&Lomb/Chiron. There are sites that promote these newer technologies outside the US to US citizens that you may visit.

VISX has recently introduced a successor to the current VISX Star laser called the S2 that will have true scanning and multiple, simultaneous ablation beams and improved centration ergonomics. Although technically still a broadbeam laser, the beam splitting technique utilized appears to improve the results compared to the Star. The S2 is required to do hyperopic ablations which were approved in late 1998. Star lasers are field upgradeable to S2 capability. Currently in research is the "S3" laser which may have treatment capabilities for Irregular Astigmatism, a growing problem for some PRK and LASIK postops. The availability timeframe for this is not known.

Another type of instrument known as the 'waterjet' is being proposed as a replacement for the blade scraping, chemical dissolving, rotary brush removal or laser 'burn off' of the epithelium for PRK procedures, as well as a possible replacement for keratome blade cutting of the flap for LASIK.. Two vendors, Visijet and Medjet, are conducting clinical trials of the waterjet device. The device uses a mciroscopic pulsed stream of water to cut the cap for LASIK or a diffused stream for removal of the epithelium. These waterjet tools will NOT have to go through the same FDA review standards as PRK or LASIK since it will be considered a 'substantially equivalency' device to those currently in use for these cornea 'preparation' purposes.. Medjet is also doing preliminary research to use the water to replace the excimer for tissue sculpting, but this will require studies similar to those for excimer lasers, and would be several years away. In any case, you can visit the Medjet website to review their 'claims'.

Other laser types proposed include holmium that 'thermally' shrink collagen in small circular spots around the central optical zone in a procedure called Laser Thermal Keratoplasty (LTK). The picture to the left is a post Holmium LTK cornea, and you can see the 'thermal burns' as circular spots. Pictures IMMED1 and IMMED2 were taken within 48 hours of treatment. IMMED1 using two 'rings' of thermal burns where the second ring is offset from the first, while IMMED2 shows the two rings aligned. One or two rings may be used, and the number of thermal burns per ring do vary dependent on the correction attempted. The third photo 6 WEEKS shows that the cloudiness where the heat was applied has cleared considerably. LTK is considered by some to be safer than PRK or LASIK since no cutting or ablating or tissue ocurs. Where the laser's energy is applied, the collagen within the cornea stroma 'coils' and shrinks. This produces a 'cinching' effect that results in a steepening of the area within the rings, thus a reduction in hyperopia. Current trials for upto 3 diopters of hyperopia (up to +3) appear to be good, but regression has been a problem, especially in attempts larger than +3 diopters. Clinical trials are continuing. The FDA may approve LTK from Sunrise Technologies in mid 1999 for low hyperopia. Problems with holmium include collagen regeneration, induced astigmatism, cornea 'burn', epithelial defects, and regression (note: this list in not conclusive). LTK has been promoted as a method to correct 'overcorrections' after PRK or LASIK, and this may prove to be the best treatment for PRK and LASIK patients who are rendered farsighted (versus an additional hyperopic PRK or LASIK treatment). The pool of overcorrected PRK and LASIK is expanding fairly rapidly as myopic PRK and LASIK volume grows,and these patients are usually under +3D overcorrected, and appear (based on available studies which are limited) to respond well to LTK to pull them back toward emmetropia or myopia. LTK does not treat astigmatism currently, but is in experimental trials. Another laser called the YDF laser attempts to vaporize tissue within the stroma without destroying the epithelium and Bowman's Membrane first. The vendor that attempted this surgical method was Intelligent Surgical Lasers (now defunct) and the procedure is called intrastromal photorefractive keratectomy (I-PRK). Extremely complex, I-PRK was promoted as able to overcome the problems of excimer direct surface ablation (and preservation of an intact Bowman's Membrane and epithelium regeneration). The technology was sold to another medical company who is attempting to revise the laser as a LASIK capable laser. This is experimental.

There are three non-laser techniques currently in FDA trials. The one furthest along is intrastromal corneal rings (ICRs) also known as intrastromal corneal segments (ICSs) that are implanted in the cornea and can supposedly be 'removed'. The vendor of ICRs is Keravision. ICRs/ICSs (marketed as "intacs") are controversial because they are invasive and require significant skill during wound creation and insertion. The ICR/ICS results are mixed and it is still invasive surgery requiring incisions into the cornea (about half to two-thirds of the cornea depth) and somewhat brutal ring insertion techniques. The two segments are inserted, one on each side, in the midzone. Different thickness of segments causes a torquing of the central cornea resulting in 'flattening' and thus reduction of myopia. Even if the rings could be removed, that would be another invasive surgery, and additional scarring and wound healing would occur. Many surgeons claim ICR is "reversible", but this claim is limited. ICR/ICSs can be seen with the naked eye with close observation and oblique lighting (see photo to the left, see arrow). ICRs are in Phase III (final stage) FDA trials for low myopia and no or minimal astigmatism.

In the example to the left, the segments are clearly visible, and can be observed with the naked eye. Some have described it as a "cyborg' eye. You can also see a circular 'cloud' or ring of iron deposits that form around the inside periphery of the segments. Iron lines also form after PRK and LASIK. They do not seem to cause significant long term risk to the eye, but long term observation will be necessary.

In the example to the left, you can see the formation of epithelial deposits and scarring (fibroblasts) around the cornea segments. There are also opaque deposits or precipitates that may have been 'drug' into the wound tunnel during insertion. Obviously, the ring segments do affect night vision producing glare and halo effects. The larger the pupil, the more severe the effect. Known complications of Intacs (Cornea ring segments) are (partial list): overcorrection, undercorrection, induced astigmatism (regular and irregular), pain, inflammation, infection, night vision problems, perforation, wound infiltrates, suture irritation (the entry wound is currently sutured closed after insertion), epithelial erosion, and scarring. In January 1999, the FDA Ophthalmic Advisory Panel recommended conditional approval for the Keravision Intrastromal Cornea Segments. FDA final approval is expected by Spring 1999. For more information on the approved range and the safety and effectiveness of this procedure, visit the Keravision web site at www.keravision.com or do appropriate search engine searches.

A 'new' version of corneaplasty has also been proposed. In this version of Ortho-K, a 'chemical' is instilled/injected into the cornea to 'break chemical bonds' making the cornea 'malleable' and easier to mold with custom RGP lenses. It is only in very early FDA trials, and no reliable details regarding its safety, effectiveness and side effects are currently available. Recently the FDA did approve a specific contact lens, the Contek, for ortho-K treatment (without the 'chemical' component) for up to 3D of myopia, however, ortho-k is not without risks, and a 'retainer' lens must be worn at least once a week to maintain the altered cornea shape.

A third technique is intraocular contact lens (ICLs) manufactured by Staar Surgical. This lens is placed behind the iris, and before the eye's natural lens. Another type of ICL is placed between the cornea and iris. One type uses claws to imbed and lock into the iris, while another using tension springs pressing against the sclera (before it transitions to the cornea). In these highly invasive procedures, a surgical cut is made at the top of the cornea (all the way through it) or cornea edge (where the cornea meets the white sclera), and a foldable intraocular lens (IOL) type 'contact lens' (similar to those used for cataract surgery) is pushed through the wound and placed in front of the iris (tension or Worst claw ICL) or between the iris and the natural lens (Staar ICL). The Staar ICL has extended edges that hold it in place between the iris and the sac that hold the natural lens. Known complications are iris inflammation, glaucoma, cataract. Iff the ICL is not placed correctly or does not 'seat' properly, it may irritate the iris, or worse, touch the natural lens behind the iris resulting in a cataract within days or weeks of the surgery. If the lens is placed successfully and does seat properly, visual acuity can be exactly corrected, and very large degrees of refractive error may be corrected. Iris distortion, large amounts of epithelial cell loss, cataracts, glaucoma and retinal hemorrhage are known complications from clinical trials. The concept of performing invasive surgery inside the aqueous humor (the chamber between the cornea and eye) or between the iris and natural lens in a healthy eye are extremely controversial. The possibility of vision threatening complications should make anyone but those with the most serious refractive disorders wary.

Pretty much all of the complications described within this site are applicable to these newer techniques. The Usenet newsgrouop sci.med.vision may be your best source for reviewing/inquiring about these procedures.

Because the potential market is so lucrative and the demand so strong, refractive surgery and a wide variety of techniques are here to stay. It will be up to the individual consumer to research the feasibility, safety and effectiveness of any surgical procedure they contemplate (in the US and abroad). It's a good idea not to be a guinea pig for experimental or investigational surgery, especially if it's elective. It is also a good idea to go to an experienced surgeon you have thoroughly checked out. It's an individual decision and there are many patients that have results they consider a great success and decided before having surgery that the possible benefits were greater than the possible risks.

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Refractive Surgery Hype and Euphemisms

The English language (as do most languages) relies heavily on vague and subjective terms. Many terms are highly subjective, and may be interpreted to mean very different things by different people since each bring his own perspective to any issue. Some terms like 'some' and 'most' are so basic to language they are unavoidable. However, when these terms are used in the process of making critical decisions such as evaluating refractive surgery, caveats are in order. This is true of the literature and opinions regarding refractive surgery. The marketing material most patients review often contains vague claims and 'general' conclusions. The use of 'most', 'almost all', 'rare', 'significant' and other vague quantifiers is universal. Even EyeKnowWhy can't get away from them in this document! Therefore, the following provides a list of refractive surgery euphemisms, vague quantifiers, and slang you will encounter in the world of refractive surgery.

Because refractive surgery is controversial, it is no surprise that derogatory slang has developed. This list is not intended to 'indict' all refractive surgeons as greedy, unethical, incompetent and uncaring. In fact, many refractive surgeons are truthful with patients regarding the risks and believe in the surgery. However, there is a sizable minority who are financially motivated and it is up to the patient to be sure they are getting the best surgical procedure by the best surgeon.

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Summary of Complications of Refractive Surgery (List and Summary)

It is impossible to name all complications of refractive surgery or accurately define percentages, severity, and duration. The reason is simple however - all human corneas heal differently (even corneas in the same person). That is, each cornea (and the eye itself) responds to trauma differently.

The following table, Refractive Surgery Complications - List Only, attempts to list known complications. An additional web page Refractive Surgery Complications - Summary and Discussion provides a summary with the frequency and characteristics for the applicable refractive surgery procedures (RK, PRK, LASIK). For greater detail or understanding of a particular complication, it will be necessary to visit your nearest medical school library.