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Risks & Complications

Understanding Risks

The most difficult part of the journey for any patient considering LASIK is the process of accepting that no surgery can be guaranteed. We can reduce our risks substantially by selecting an experienced surgeon, advanced LASIK technology, and a professional clinic, but there are still no guarantees for a great outcome. Even if only one patient in five thousand develops a certain complication statistically, it is 100% when it occurs to that patient. This is a very difficult and frightening concept to grasp, but one that every patient undergoing any procedure must recognize. We thoroughly believe in the potential of Custom All Laser LASIK with the Schwind AMARIS 750S laser system to effectively and safely correct a range of prescriptions, but we do not want you to ever feel we are making the procedure sound too easy or simple, or that the procedure is perfect or guaranteed. Read more...

The next important concept is one of shared responsibility. Both the patient and the clinic must work toward a positive final result. Each patient must become informed, learning about the procedure, the technology and the clinic they select. They must recognize not simply about the potential of this procedure to provide independence from glasses but also the potential for side effects and complications. As you will learn, there are several steps in preparing for the procedure, and several important measures you must take after your procedure to ensure a safe recovery including using the medications as prescribed and attending each scheduled post-operative appointment. We hope that you will take advantage of the information provided to you within our website, through your personalized patient link, from our staff and Dr. Machat. Your eye doctor is another excellent source of information as are friends and family members who have had LASIK. Please remember that if you do not invest the time to educate yourself, and follow the instructions it is possible that your results may be compromised.

The third aspect of being fully informed and prepared, is that of having realistic expectations. This is one of the most important concepts, as 20/20 is a quantitative visual measurement and not a measure of success. While statistically most patients within our prescription range will achieve 20/20, some patients will not, due to the variability in healing patterns between patients. We do understand that achieving 95% vision is still 5% blurry, but our primary goal is your safety, not perfection. When the remaining prescription is very small, it may be medically unwise or unsafe to perform additional laser surgery to enhance the visual result. During the first year there will be no charge for an enhancement, but more importantly there is additional risk associated with an additional surgery and you and your surgeon will decide whether or not it is a reasonable option. In general, as we have learned from past LASIK patients, it is sometimes best to appreciate the vision gained rather than focus on the fact that 20/20 was not achieved. All surgeries carry risk, and even if the prescription is small, that does not reduce the level of risk. In fact, some surgeons believe that the level of risk with enhancement procedures is the same or greater than with the initial LASIK procedure. Hide...

Understanding Complications

It is important to review the informed consent video and gather as much information as possible. The test questions help ensure that you have acquired a level of understanding and appreciation for the major issues presented. Read more...

Side effects and complications can be divided into several sections in order to better appreciate their significance. We will present LASIK problems in two different ways in order to help you fully understand both the common and rare problems you may encounter. We will also highlight some of the safety measures that we have introduced to help reduce these problems however at no time do these measures completely eliminate your risk:

Most common complaint Dry Eye
Most common side effect Night Glare
Most serious complication Corneal Ectasia
Most common treatable complication Over or undercorrection or response
Most common serious Surgical Complications
Most common serious complications during Healing phase

Another way of looking at the problems that can occur with LASIK

Refractive (Prescription) PROBLEMS
  • Over response
  • Under response
  • Residual prescription
  • Induced astigmatism
Surgical Phase
Early Healing Phase
  • Pain / discomfort
  • Dryness
  • Keratitis
  • Glare
  • FB sensation
  • Striae
  • DLK
  • Infection
Late Healing Phase
Vision Quality Side Effects
  • Night glare
  • Irregular astigmatism
Most common serious complications during Healing phase
  • Irregular astigmatism: loss of sharpness, crispness and clarity
  • DLK – immune inflammatory reaction
  • Infection

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What we do to help reduce your risks:

Severe Dry Eye Read More...

Severe dry eye is marked by symptomatic dryness, foreign body sensation, blurred vision, corneal inflammation, intolerance to contact lens wear and even breakdown of the surface protective layer of the cornea. Patients with severe dry eye are not considered LASIK candidates at Crystal Clear Vision. As many as 50% of those patients seeking LASIK surgery, have some degree of dry eye symptoms. Many have difficulty wearing contact lenses, which is what prompts them to consider surgery. However most can and have been treated with LASIK successfully. While some studies have demonstrated that a surface laser vision correction procedure (PRK) is best for dry eye patients, other studies show an All Laser LASIK procedure to be equally safe. The most important thing to realize is that all laser vision correction procedures will increase the risk of dry eye symptoms. In fact, 100% of all LASIK patients experience dryness symptoms immediately following surgery, although the overwhelming majority, improve to their pre-surgery status within three to six months. The patients that remain symptomatic with blurred vision and significant and often painful dryness are those with severe untreated dry eye before surgery. The risk also is higher for those with severe prescriptions and especially females over forty years of age treated for farsightedness. While most dry eye patients benefit from artificial eye drops, some require ointments, topical steroid drops, bandage contact lenses or even a clinically proven immunosuppressive prescription medication, Restasis®. Today many patients are pretreated with artificial tears and even Restasis® to optimize the tear film and ensure that the corneal surface is healthy prior to surgery, however this medication without a drug plan is expensive and remains the responsibility of the patient.

By only offering All Laser LASIK, we reduce the dry eye risk associated with a mechanically created flap. As well, Crystal Clear Vision will mandatorily screen all patients with dryness symptoms using a highly specialized equipment, TearLab. Any positive test result will require the patient to either undergo pre-operative therapy with repeat testing in three months, or simply canceling their LASIK procedure. The $40 testing fee is deducted from the cost of the procedure if the patient is still deemed a candidate or receives adequate therapy and passes on retesting. Our goal is to ensure your safety and satisfaction, and we believe it is far easier to avoid problems than to manage them once they occur. Hide...

Night Glare Read More...

Symptoms of night visual disturbances such as halos, starbursting and glare can occur following LASIK, and were common with older laser technologies using standard laser patterns. Patients with higher prescriptions, greater degrees of astigmatism and larger pupils were more likely to experience these symptoms. Some patients experienced such disabling degrees of night glare that it affected both their ability to drive at night and the quality of their vision under low light situations. As the pupil enlarged in dim light, it became larger than the treated area therefore allowing unfocused light to enter the eye and scatter.

Wavefront technology

Two technological advances that reduced this risk substantially were the creation of larger treatment zones and the application of Wavefront technology. Wavefront technology was first used in giant telescopes to reduce the atmospheric disturbances or aberrations that distort the images of distant stars and planets. Essentially, the image is broken down into a grid pattern creating small pixels, which are then individually sharpened to improve the overall astronomical image. For the eye, a Wavefront Analyzer is used to create a Wavefront map, which essentially applies a similar grid pattern to the eye, examining light rays that enter across the cornea through the pupil. Instead of a single prescription reading measured through one central point, as is used to make your glasses, a prescription map is created. This prescription map, more commonly referred to as a Wavefront map, is the prescription at each grid coordinate, essentially defining the prescription required to precisely focus light rays at every point across the pupil in dark lighting. As such, not only are the central light rays precisely focused but peripheral light rays are focused as well. The Wavefront map is then used to create a Custom laser pattern for each eye of the patient, which then guides the computerized laser to reshape the eye accordingly. This is what is meant by ‘Custom’. No two eyes have the same pattern, like fingerprints, Wavefront maps are completely unique to each eye. Using a customized treatment pattern targets the optimal corneal shape, for the best quality vision post operatively, however it must be understood that patient healing always results in some degree of variability.

The Wavefront or prescription map can be composed of tens of points, hundreds of points but in the case of the Schwind AMARIS 750S, more than a thousand points of measurements are utilized, providing a far more sophisticated customized treatment plan for each patient.

One of the advantages of Wavefront technology is that when our pupils naturally expand under low light conditions, the peripheral light rays are now better focused, reducing the light scattering which produces night glare, halos and starbursting. Many LASIK surgeons including Dr. Machat have reported that with Custom LASIK, the severe disabling night glare that was frequent with older standard laser technologies has not been observed, even in those patients with naturally larger pupils. For this reason, Dr. Machat only performs Custom All Laser LASIK, as he strongly feels this is a much safer and better quality procedure for his patients and the only one he would have himself or perform for his friends and family. Dr. Machat was the first surgeon in Canada to perform Custom LASIK in March 2000, and one of the first handful in the world. Hide...

Corneal Flap Complications Read More...

The most common serious surgical complication is the occurrence of corneal flap problems created by a mechanical microkeratome used in traditional or Standard LASIK. For this reason, Dr. Machat only creates corneal flaps utilizing a Femtosecond laser. The precision and the reproducibility of the Femtosecond laser flap, is an added safety measure that dramatically reduces the risk of corneal flap problems. The computerized laser system helps ensure the quality of the corneal flap as well as allowing Dr. Machat to customize the depth and shape of the flap accurately. Dr. Machat was the first surgeon in Canada to create a corneal flap with a Femtosecond laser and the first to perform Custom All Laser LASIK in 2003. Hide...

Refractive Problems Read More...

The most common treatable problem is a refractive or prescription issue. Simply stated, not every patient treated achieves 20/20 vision, primarily due to variability in healing. In general, the eye looks at the laser procedure as an injury and tries to heal back to its natural state. For this reason, lasering beneath a corneal flap helps ensure the stability of the new shape change. However some patients after their procedure find that they still have some of their residual prescription remaining, as they have under-responded to the laser treatment while others, over-respond. While this can be treated with an additional laser application beneath the existing corneal flap, patients must wait a minimum of three months but ideally less than six months. It is possible that over time as the cornea heals, the vision will improve, so retreating early must be avoided. Similarly, some patients are perfect initially but find that their vision regresses during the three month healing process as the body tries to repair “the injury”. The ability to re-lift the corneal flap beyond six months becomes more difficult, so for this reason the three to six month time frame is best.

The most important considerations with any enhancement or retreatment procedure are whether it is medically safe and whether the potential benefits outweigh the risks.. The surgeon and patient must balance the level of vision that has initially been achieved and the potential for gain, against the risk of developing complications. At Crystal Clear Vision, any enhancement required in the first year will be performed at no charge, if medically safe, as this is due to an under or over response of the eye. After that time any changes that occur are due to an actual change in your prescription. If an enhancement is required for that reason, there will be a charge of $500. Enhancements should not be taken lightly. While most patients do achieve 20/20 and are pleased, we hope that patients with residual prescriptions will understand that we cannot control the healing variability and that the decision to proceed with further surgery must be medically indicated and safe. Hide...

Corneal Ectasia Read More...

The most serious complication is the development of Corneal Ectasia. This occurs when there is a loss of corneal stability or strength resulting in thinning and bulging of the cornea. There is a lot of confusion and controversy surrounding this complication. This condition is believed to result from excessive tissue removal or excessive depth of penetration of the cornea during the LASIK procedure.

If one considers a book analogy to understand the cornea, the average cornea is 540 pages or microns thick, but ranges in the general population from 470 to 630 pages. In LASIK, the corneal flap is 100 to 160 pages, and the tissue removed with the prescription correction 30 to 150 pages. The FDA has recommended that the stromal bed, the remaining untouched corneal tissue, should be at least 250 microns. Therefore in a typical patient having LASIK, with a corneal flap of 120 pages and a laser correction of 70 pages, the remaining untouched stromal bed would be 540-120-70 = 350 microns. Well above the minimum FDA guidelines. If however, a mechanical microkeratome creates a corneal flap of 160 pages, and an extremely nearsighted person is treated close to the maximum of 140 pages, then the remaining tissue would only be 240 pages or microns. One can now see how the treatment of very high prescriptions or the creation of thicker corneal flaps can be a cause of concern. It also is crucial that accurate corneal thickness measurements are taken before the surgery. What confuses the issue though is that many patients who had been treated in the early days of LASIK, without these guidelines, have stromal beds of 200 to 220 microns (well below current FDA guidelines) did not develop corneal ectasia, while there are an unfortunate group of LASIK patients with more than 250 microns, some even more than 300 microns of residual stromal tissue who did.

Due to this, some surgeons believe that the problem with these patients is not excessive tissue removal but an undiagnosed corneal condition. The two related corneal diseases are Clinical Keratoconus, and Pellucid Marginal Degeneration. Clinical Keratoconus occurs in about 1% of the population however Pellucid Marginal Degeneration is much less common. Both these corneal diseases can result in an abnormal healing response, and a loss of corneal stability after LASIK. Patients may note a worsening of their prescription immediately after their initial LASIK procedure or following an enhancement procedure, but corneal ectasia may even manifest itself months or even years later. Typically these patients become nearsighted and develop severe astigmatism distorting the quality of their vision. Glasses may help initially but eventually specialized gas permeable lenses are required. Although not yet FDA approved, there is a treatment available for corneal stabilization called Collagen Corneal Crosslinking, which was developed and pioneered in Europe. In this technique, the epithelial protective layer is typically removed and Riboflavin eye drops instilled, while Ultraviolet light is applied for thirty minutes. The ultraviolet light activates the riboflavin and results in increased linking between the collagen layers strengthening the cornea. Some surgeons have combined this technique with further laser surgery in an attempt to reduce the astigmatism and improve the vision as well. In the past, aside from contact lenses, the final option was a corneal transplant, which may still be required for patients that cannot achieve acceptable results from other techniques.

Crystal Clear Vision screens each patient in order to identify Clinical Keratoconus and Pellucid Marginal Degeneration pre-operatively. The multidimensional corneal analysis system is designed to identify corneal disease, however in some younger patients the condition may not manifest itself until years later. While it may be possible to do a laser procedure at 18, it is highly recommended that you wait until at least 21 years of age and those with any suspicious corneal map changes or family history of corneal disease are asked to delay LASIK surgery until at least 25. Our approach is simple, if there are tests or guidelines to reduce the risks for our patients, Crystal Clear Vision will adopt these measures. We do not offer LASIK to everyone, but to those that we do accept we will do all that we can to ensure their safety.

Although the risk is very small that a patient will develop Corneal Ectasia, likely in the order of 1 in 5000, or 0.02% or less in Dr. Machat’s experience, he always utilizes a Femtosecond laser to create each and every corneal flap. He was the first Canadian surgeon to adopt this more advanced, safer and more costly technology in 2003 with the belief that safety must be the overriding consideration when laser vision correction is performed. The ability to create thinner more predictable uniform thickness corneal flaps customizable to the size and shape of the eye is what differentiates a Femtosecond Laser created flap from a mechanical microkeratome Standard flap. This advantage reduces the risk of corneal ectasia. Furthermore, the AMARIS 750S excimer laser system at the Crystal Clear Vision clinic is equipped with online pachymetry, a rarity in these systems, capable of measuring the corneal thickness continuously during each step of the LASIK procedure, providing even further safety for Dr. Machat’s patients. Both these laser technologies in Custom All Laser LASIK add to the clinic cost of the procedure for Dr. Machat, but not to his patients, what they do add to his patients is safety and peace of mind. Hide...

Decentration Read More...

A decentered laser treatment or decentration is a surgical complication that occurs when the laser treatment pattern is not correctly centered upon the pupil and visual axis. This complication, which was a major concern with early laser platforms has been essentially eliminated as a surgical risk with the introduction of advanced eye tracking systems. A decentration typically resulted in night glare symptoms and induced astigmatism, often reducing the patient’s quality of vision. Many patients biggest fear, in the early days of laser treatments, was that they would move their eye during the procedure. Today, with infrared eye tracking systems based on missile guidance technology, laser pulses are very accurately placed during the half minute long procedure. Even with significant eye movement, the system is able to follow pupil movements and ensures correct placement, temporarily shutting off with excessive movement. With AMARIS Custom LASIK, the eye tracking technology actually takes the accuracy one step further. While the majority of laser platforms have three dimensional eye tracking technology, the Schwind AMARIS 750S laser technology used at Crystal Clear Vision possesses an advanced six dimensional Eye Tracking system for your added safety. Hide...

Pain/Discomfort/Epithelial Defects Read More...

During the LASIK procedure, the protective layer of the cornea, known as the epithelium is preserved. This is in sharp contrast to surface laser procedures such as PRK or photorefractive keratectomy, where the epithelial protective layer is removed. The removal of the protective layer results in a slower and more painful visual recovery usually taking three to five days rather than one day. A bandage contact lens can be inserted with PRK to improve the vision and comfort during this time. Most LASIK patients only have an hour or two of discomfort if any, and it is usually described as a foreign body or eyelash sensation. This sensation is irritating and is observed immediately following the LASIK procedure as the edges of the corneal flap heal. The best remedy for this discomfort is sleep, as the edges heal very fast during rest.

Occasionally, LASIK patients will develop larger defects in the epithelium, either due to a genetic weakness in the protective layer, age, dryness or surgical trauma. In such cases, patients will experience pain and irritation for a longer period of time and a bandage contact lens will be inserted to improve comfort. The development of increased inflammation, known as Diffuse Lamellar Keratitis and Infection must also be monitored when such an injury occurs, and additional anti-inflammatory and antibiotic drops are often indicated. Lastly, Epithelial Ingrowth may develop, whereby the healing epithelium grows beneath the flap, and requires that the corneal flap be lifted and the interface cleaned. Usually there is no long term risk associated if managed early. Hide...

Diffuse Lamellar Keratitis Read More...

Diffuse Lamellar Keratitis or DLK (also known as “Sands or Sands of the Sahara”) is an immune mediated inflammatory reaction that occurs at the level of the interface where the laser correction was performed. It is not well understood. It is believed to be a form of a hypersensitivity or allergic reaction to something that the eye is exposed to during surgery. It usually occurs within the first few days following LASIK with patients complaining of glare and blurred vision, but no pain or discharge. A faint haze is noticeable at the level of the interface upon microscopic examination by your doctor, and appears to look like grains of sand, hence the nickname. Topical steroid drops are the treatment for DLK to quiet the inflammation, but if unresponsive after careful monitoring, the corneal flap is lifted and the interface cleaned. Most patients respond well and visual recovery is usually quite good, however the key element is early identification. It is important that all LASIK patients see their eye doctor in accordance with the recommended post-operative care schedule and inform their doctor or Crystal Clear Vision should they notice any unusual change in their visual recovery. Hide...

Corneal Striae Read More...

Corneal striae or wrinkles occur when the corneal flap is displaced out of natural alignment. The corneal flap is usually hinged at the top beneath the upper eyelid and any injury even minor during the first few days can displace it. Even a patient squeezing their eyes very tightly can occasionally move the corneal flap and produce wrinkles. Patients are encouraged to wear protective eye shields at bedtime for the first two nights and wrap around sunglasses for the first four days. The greatest risk of corneal flap movement occurs during the first night, when the eye is irritated as patients have a higher tendency to squeeze or rub their eyes. Surprisingly though this problem occurs quite infrequently, and again is significantly minimized by the use of a Femtosecond laser to create the corneal flap.

Treatment usually involves the surgeon lifting the flap and smoothing it back into alignment. The eye is usually a little sore and blurry for a few days. Patients are placed on antibiotics and anti-inflammatory drops again during the recovery. Sometimes with very minor corneal striae, the flap does not need to be lifted to smooth the wrinkles as the vision is not affected.

The development of increased inflammation, known as Diffuse Lamellar Keratitis and Infection must also be monitored when such an injury occurs, and additional anti-inflammatory and antibiotic drops are often indicated. Lastly, Epithelial Ingrowth may develop, whereby the healing epithelium grows beneath the flap, and requires that the corneal flap be lifted and the interface cleaned. Usually there is no long term risk associated if managed early. Hide...

Irregular Astigmatism Read More...

Irregular Astigmatism following LASIK is a term used to describe corneal irregularity that is not correctable with glasses. An analogy for irregular astigmatism is that of wrinkled aluminum foil. If one pulls out a fresh sheet of aluminum foil and shines a flashlight, there is a clear reflection noted. If however, the sheet of aluminum foil is crunched into a ball, then straightened out, when a light is shined on the wrinkled sheet, the light scatters in many different directions.

Although infrequent, there are a variety of causes for Irregular Astigmatism following LASIK. These range from surgical to healing related causes. When the cornea has a significant degree of Irregular Astigmatism, the image is blurred and the best vision with glasses is reduced, meaning usually that the bottom lines of the eyechart cannot be read clearly. There is a loss of sharpness, crispness and clarity with Irregular Astigmatism. In mild cases, patients are often able to read the entire eyechart, however they find the letters qualitatively blurred or distorted.

Irregular Astigmatism brings to the forefront the concept of visual quality versus visual quantity. For most people, the goal with LASIK is to be independent of their glasses and contact lenses, however the quality of the vision is equally important to the quantity of vision. Visual distortion or blurriness of the letters on an eyechart or ghosting of images or light sources can be very debilitating. Advanced laser systems like the AMARIS 750S, using Wavefront technology substantially reduces the risks of such occurrences, but as has been stated previously, do not eliminate these risks entirely.

Excimer laser programs based upon corneal curvature maps may be able to improve irregular astigmatism for specific cases, such as Decentration. Other surgical causes such as a corneal striae or wrinkles, are treatable, however with many healing related causes time is the only course of management. In these cases, a gas permeable contact lens is recommended in order to provide a smooth surface. These contact lenses usually restore excellent vision. Hide...

Infection Read More...

Infections can be extremely severe and sight threatening. It is the most easily understood complication but also one of the most potentially devastating. The symptoms are typically pain, redness and yellow-green discharge from the eye. Some patients will notice a white spot on their eye as well, which is where the corneal ulcer is located, the central focus of the infection. Infections usually occur during the first week following LASIK, usually during the first 48 hours. Patients with a drop in vision, increasing pain or eyelids sticking together must be evaluated on an urgent basis using the 24 hour emergency number.

Depending upon the virulence of the bacterial strain or other microbial agent, the urgency of treatment is the most critical factor in the visual outcome. In general, the identification and treatment of any active infection prior to LASIK, the use of a fourth generation flouroquinolone antibiotic drops and a careful follow up regimen are important elements in protecting against infection. Hide...

Recurrent Corneal Erosion Read More...

This condition is the repeated breakdown of the surface protective layer (epithelium) in a localized area. It can be either related to a genetic weakness or trauma. It is not uncommon for some patients to have a history of a corneal injury usually related to a finger poke in the eye, tree branch or other similar history. The patient then notices pain and tearing upon waking up in the morning with a foreign body sensation, which then often clears in a few hours without treatment. However, the patient will describe a recurrent pattern of awakening with these symptoms every few weeks or months. The cause is usually related to damage to the underlying “cement” known as the basement membrane that glues the protective layer to the corneal tissue beneath. When the patient opens their eye in the morning, the protective layer sloughs off with the lid movement and the patient notices the pain or discomfort.

Two issues can arise with LASIK. First, surgical trauma that can create an epithelial defect or abrasion could potentially produce recurrent corneal erosions if the underlying basement membrane is damaged. Secondly, patients with a history of recurrent corneal erosion prior to their LASIK procedure will often experience a reoccurrence at the time of surgery as this area is already weakened. In patients with a genetic weakness, known as an epithelial dystrophy, of their “cement” the entire epithelium is at risk to slough, and the LASIK procedure can result in a large corneal abrasion with significant pain, and slow visual healing. These patients are managed with a bandage contact lens, and topical steroid and antibiotic drops to help reduce the associated discomfort and the risk of infection and DLK.

Pre-operatively, patients are examined for any evidence of an epithelial dystrophy and patients who exhibit any signs are excluded from LASIK surgery at Crystal Clear Vision, although AMARIS Custom PRK may be possible. While not always evident even under biomicroscopic examination, patients with a clear history of such symptoms are excluded from LASIK as well. These patients often do better with a surface laser procedure where the epithelium is removed to apply the laser treatment. Hide...

Blepharitis Read More...

Blepharitis is an inflammation of the eyelids and eyelashes, which is often associated with bacteria in response to their toxins. It is a common condition but varies widely in severity and must be managed pre-operatively to ensure that no bacterial infection is present at the time of surgery. Patients are screened for Blepharitis prior to surgery and treated if any clinical findings are found. LASIK surgery must be delayed when uncontrolled Blepharitis is diagnosed. Rarely, even treated Blepharitis can reactivate following LASIK surgery and can lead to corneal infection or inflammation. Hide...