LASIK Myths and Facts

Myths, Truths, and Valid Concerns about Laser Vision Correction

Nicole Lemanski, M.D. and Evan D. Schoenberg, M.D.

Over thirty million people have benefited from laser vision correction (LVC) — LASIK, PRK, SMILE and a smorgasbord of related acronyms — and it is easy to understand why they celebrate their successes.  Over 97% of people who have LVC see 20/20 or better[1] and 99.5% see 20/40 or better[2] without glasses or contact lenses. Satisfaction with LASIK is better than 99%.[3] There are unfortunately many misconceptions and myths related to laser vision correction among the general population. This has led to confusion, misrepresentation, and spreading of partial truths, especially online and in the media — sometimes shared by well-meaning people and sometimes driven by a handful of vocal zealots who claim to speak for a larger, invisible whole.  We have set out here, utilizing peer reviewed scientific data, to close the gap in knowledge and to set the record straight.

Who can get treatment?

Myth: LASIK is only for young people

Fact: The majority of LVC patients are between 18 to 45 years old, have healthy eyes, see well with corrective lenses, and wish to be more independent of glasses or contacts. LVC can be performed at any age, but it may be performed in a different manner for patients of different ages. A 28 year old patient is treated differently than a 48 year old. Why? While a 28 year old still maintains the ability to focus their eyes for close vision (called accommodation) , a 48 year old may already be noticing some changes in their reading or close vision. There are options to address each of these patients visual and functional needs and still allow them to remain as spectacle independent as possible.

As age increases beyond 45 years, it is possible that a lens-based surgery (e.g. cataract surgery) may be another reasonable approach to long term vision correction, since the body’s natural lens otherwise continues to develop into worsening cataract.  Even with a lens-based surgery as the initial approach, LVC is commonly used afterward to refine vision if needed.


Myth: LASIK is just cosmetic

Fact: LVC corrects refractive error. There are many reasons a person may choose LVC besides just not wanting to actually put glasses on. Some patients with LVC have only ever worn contact lenses.  There are patients who have had difficulty with contact lenses for a number of reasons: dexterity issues, allergies to lens polymers, or a history of past infections. There patients without the use of their upper extremities, who are unable to lift glasses to their face.  LVC relieves people of their need for artificial vision aids, allowing them to function unaided in challenging situations — including the high-impact needs of first responders, laborers, athletes, and professionals of all sorts.

Myth: LASIK can’t treat astigmatism

Fact:  Normal (“regular”) astigmatism is just part of a glasses prescription. LVC reshapes the cornea, thereby treating the glasses prescription. So actually, LVC is an excellent choice for treating most regular astigmatism. Certain types of LVC (called Topoguided LVC) were made specifically to treat “irregular” astigmatism, which can be difficult to correct, even with the best glasses. This type of laser takes into account each patient’s individual corneal shape. After this shape is mapped, a custom treatment is used to correct astigmatism and regularize the shape of the cornea.  The earliest versions of the procedure, in the late 1990s and early 2000s, couldn’t treat astigmatism, giving rise to this misconception.

Myth: PRK is old, and LASIK is newer and better

Fact: In some cases, LASIK is the better choice; in others PRK is.

It is true that PRK has been around longer. The first LVC procedure was PRK, utilizing the excimer laser. PRK, also called “advanced surface ablation” (ASA) or LASEK, involves removal of the skin layer of the cornea, the epithelium. The precise technique to remove this layer varies. A very recent advance called “transepithelial PRK” is available only outside the United States as of 2020 and can be of particular help when treating diseased or irregular corneas. Once the epithelium is removed, the excimer laser reshapes the cornea, thereby treating the glasses prescription. A clear bandage contact lens is worn while the epithelium heals and the vision improves.  PRK can be the best choice for some patients, especially those at unacceptably high risk for eye trauma, such as mixed martial arts fighters, or for those with thinner corneas.  However, it does have a long healing process — it is often three months or more for the eye to reach its final healed state.

LASIK’s innovation is to work inside the cornea rather than its surface.  In the early days of LASIK, a special blade called a microkeratome was used to create a partial thickness flap in the cornea, about 20% from its surface.  Today, about 75% of LASIK uses a femtosecond laser to create this flap instead of the blade. Either way, once the flap is created, the remaining steps are the same. The flap is folded back on a hinge to expose the underlying cornea tissue which is reshaped with the excimer laser, thereby treating the glasses prescription. This flap is then put back into place. Because only a microscopically thin semi-circular sliver of the cornea surface is affected, comfort immediately after LASIK is much better, and because the skin doesn’t need to regrow, visual improvement is much faster, with a majority of patients seeing 20/20 the day after surgery.

Partial Myth: Some eyes have a prescription too high for treatment

Fact: This is true, for laser vision correction, which involves reshaping the cornea by precisely removing tissue. It is important not to remove too much, as this would risk making the cornea unstable. However, there are other treatment approaches, including implantable lenses to supplement the natural lens (“phakic intraocular lenses” such as ICL) and replacement of the natural lens (“refractive lens exchange”) which can treat virtually any eye that is correctable with glasses or contact lenses, no matter how high the prescription.  In extreme cases, these techniques are even combined through a process called “bioptics.”  For example, a patient with -22.0 diopter nearsighted prescription might undergo first ICL, treating the first -16.0 and turning her eye into a -6.0. She might then have LASIK for the remaining -6.0, bringing her to around zero refractive error!

Myth: Eye doctors don’t get LVC

Fact: Ophthalmologists who perform LVC surgery are called refractive surgeons. It is important to know that not all eye doctors are eye surgeons, and not all eye surgeons are refractive surgeons. Refractive surgeons pursue extra training in surgical techniques that improve the refractive state of the eye (decrease the glasses prescription) and allow people to be more spectacle independent.  Refractive surgeons know the risks and benefits of the procedures they perform intimately, so it is very revealing that refractive surgeons are 4x as likely to have had refractive surgery on their own eyes compared with the general population.[4]   Of the two authors, one (EDS) remains thrilled with his LASIK treatment ten years later and has performed it for multiple family members including his wife[5] while the other (NL) is not currently a candidate for surgery at this time, but is looking forward to future developments.


Truth: Some people shouldn’t have LASIK!

Fact: Terminology is key here. Some people might not be an ideal LASIK candidate but that doesn’t mean they can’t have LVC! Remember there are two main LVC procedures with LVC: LASIK, where a flap is created and then the glasses prescription is treated (the cornea is reshaped), and PRK/surface ablation, in which the top layer of the cornea is brushed away (no flap) and then the glasses prescription is treated (the cornea is reshaped). There is actually a third procedure called SMILE, where an internal micro-thin wafer of cornea, called a lenticule, is cut by a special laser; the removal of this lenticule via a small incision reshapes the cornea and improves the vision.  Finally, vision correction via non-laser approaches, such as ICL or refractive lens exchange, may be the ideal solution, staying away entirely from the cornea if it has issues or if other factors within the eye or the body call for a different approach..

A person who may not be an ideal LASIK candidate may be a great candidate for PRK/surface ablation. Why? There are certain parameters that need to be followed in order to create a LASIK flap safely.  The cornea should be a certain starting thickness, so a patient with a thinner cornea may be a better PRK candidate. A scar may impede the laser from cutting the flap evenly, so this individual may be a better PRK candidate. Other factors like the power of the prescription to be treated, pre-existing ocular conditions, as well as rheumatologic or systemic conditions can influence candidacy for LVC. Every person is unique and different, thus every patient should have a full eye exam with a refractive specialist to determine which procedure they are a candidate for and which procedure would give them the best outcomes.

Some people are not good candidates for any of the laser based procedures, such as those with pathologic corneal conditions that cause the cornea to be misshapen or too thin. The good news is, there are other vision enhancing options available, and with newer technologies and strengthening procedures such as corneal crosslinking, some of the LVC treatments are becoming more of a reality.

Some people aren’t good candidates now but may be good candidates later.. If someone’s glasses prescription is still changing, we generally wait for it to be stable for a year. If someone is pregnant or looking to become pregnant soon, we usually recommend waiting until after the pregnancy to perform the procedure. Why? First, it’s always advisable not to have elective procedures while pregnant, because the effects on the baby are not fully known. Second, it is known that some women’s glasses prescriptions will be worse while they are pregnant and, while they typically return to what their pre-pregnancy levels after delivering, they may have long term changes.  Third, women are more prone to dry-eye related problems during pregnancy, and this could impede surgical healing.


Is LVC successful? Are patients happy?

Myth: There’s no long term data on LVC

July 2019 marked the 20th anniversary of LASIK’s approval by the U.S. Food and Drug Administration (FDA). As of then, over 19 million LASIK procedures had been performed in the US alone, with 98 percent to 99 percent patient satisfaction. The evidence supporting LASIK is overwhelming, with over 6300 studies and reports as of July 2019, and a recent review of the best studies found them to be free of industry bias and in support of a better than 99% success rate.[6] This bears repeating: Over 97% of people who have LVC see 20/20 or better[7] and 99.5% see 20/40 or better[8] without glasses or contact lenses.

  • With over 20 years of outcomes analyzed and reported, LVC is a mature technology.  Despite that maturity, it continues to improve!

Myth: Contact lenses are safer or more effective than LVC.

Fact: A large study of results 3 years after LASIK compared to people who had been wearing contact lenses for those three years found that LASIK led to more satisfactory vision, including better nighttime vision with less glare, than contacts, as well as a lower rate of dry eye.[9]

Fact:  Infection is a rare complication of both contacts and LASIK.  At 1 year, daily contacts confer slightly less risk than LASIK, but because contact lens wear confers a daily risk, by 5 years the risk of infection is 3x higher.  Extended wear contacts are even more dangerous; the risk of infection is 3x greater than LASIK at 1 year and 22x greater at 5 years.[10]

Partial Myth: Glasses are safer than LVC

Fact: The convenience aspects of LASIK compared to glasses are obvious, but what about the safety?  Unlike contact lenses, glasses don’t carry any infection risk.  However, glasses can get misplaced, broken, or fogged.  As mentioned earlier, the US military depends on LVC, not glasses, for its active duty soldiers.  For people with low prescriptions who can see reasonably well without help, glasses may in fact be the ‘safest’ option, as zero risk is less than 0.01% risk, but if someone can’t see well enough to function without their correction, LASIK could be the difference between exiting a burning building safely or fumbling unsuccessfully for their corrective lenses.

Myth: Glasses are more effective than LVC

But what about the vision quality?  Modern LASIK can actually outperform glasses in many cases!  A thorough 2017 report on FDA trial data for three lasers showed that between 30% and 46% of eyes (depending on the laser used) saw better without glasses one year after surgery than they had seen with glasses before surgery (e.g. saw 20/15 without glasses, whereas they had seen 20/20 before).  Looking at the popular Alcon Contoura laser treatment platform, 8% saw one line worse without glasses than they had with them before surgery (e.g. saw 20/25 without glasses, whereas they had seen 20/20 previously – generally a slight difference), and 3% saw significantly (2 line or more) worse than they had with glasses.  Importantly, of the 11% whose vision without glasses was worse than it had been with glasses, correction (via glasses, contacts, or perhaps a laser enhancement) was still an option to within 1 line of vision of their starting point.[11]

Partial Myth: LVC wears off

In one sense, the change that LVC creates is permanent, as the reshaped portion of the cornea doesn’t grow back.  However, there is certainly a fractional decrease in treatment effect for many people as of 10 to 15 years after surgery.  There are multiple reasons this happens.  One is that the skin layer (epithelium) of the cornea very slowly thickens as the body tries to ‘account for’ thinning of the underlying layer of the cornea (the stroma) created during surgery by the laser. Another reason is that the natural changes of the lens inside the eye with age tend to drive a mild nearsighted shift, creating a ‘moving target’ relative to the treatment performed years prior.

Nearsighted (myopic) treatments are most common and the best studied. For low treatments (less than around -4), this fractional decrease is typically negligible.  For moderate to high treatments, there is around a 10% decrease in treatment effect at a decade or more. The good news is that if you started, for example, as a -5.00, were treated to 0.00 (“Plano”) and saw 20/20, and then regressed 10% to -0.50, you would likely still see 20/20, or perhaps 20/25. Very few people whose prescription is -0.50 feel they have any real visual problems from it.

        Another change that happens with time ‘feels’ like LVC wearing off but really represents a natural age-related change called presbyopia, from the Latin roots ‘old’ and ‘eyes’ – an unfortunate term given that it begins to impact many people in their mid-40s.  The lens inside the eye changes continuously throughout life. The lens of a young person is clear and can easily change shape to bring close things into focus, such as for reading. This focusing occurs automatically, like the auto-focus in a camera. With every few years of life this amount of focus, or, accommodative ability, decreases. By their mid 40s, many people whose vision is in focus for distance — as is achieved with LVC — start to notice it is harder to focus up close.  LASIK and related procedures bring the eyes into focus for distance but don’t change this age-related progression, which often leads people to first with hold things further away and then to use reading glasses.

With further aging, typically around 55 or 60 years old, the lens eventually turns cloudy and then is called a ‘cataract’. Everyone who lives long enough eventually develops cataracts, and this is treatable after LVC in essentially the same way it would have been treated had you been born with perfect vision.

What do people really see after LASIK?

Myth: Glare is a common complaint after modern LASIK

Any form of vision correction – glasses, contacts, or surgery – changes the way light passes into the eye and can therefore produce glare (starbursts or streaks around light) or halo (rings around light).  Even people with ‘perfect vision’ typically see some degree of these effects, which are most noticeable with bright lights on a dark background such as headlights at night

Significant glare is a rare complication after LASIK.  The more common experience is a decrease in glare symptoms!  In two FDA-sponsored studies, PROWL-1 and PROWL-2, the presence of glare and halos was dramatically reduced with patients’ spectacle-free vision 3 months after LASIK as compared with their presence preoperatively with glasses, and this effect was enhanced over further time. Another study showed that 88% of pilots who land on aircraft carriers at night found their night vision to be better after LASIK with no glasses than they did with their glasses before surgery.[12]

The early days of LVC gave the treatment a bad reputation for night time vision.  Modern treatments provide a bigger sweet spot (“optical zone”) to greatly reduce the impact of pupil size, a much smoother blend zone from the areas being treated to those not being treated (eliminating areas of light scatter), automatic tracking of the eye to help insure the treatment is correctly centered on the eye, and more.

Most people do see an increase in glare for the first month or so after LASIK, and for a few months after PRK, but it tends to fade into the background or be ‘tuned out’ after that timeframe. Many people report a little glare which they find to be easily ignored. A very small minority of people do report a long term increase in troubling glare after the procedure. Residual prescription (treatable) and dry eye (treatable) are the most common reasons for glare, but other factors can be at play, as well. This brings us to the next topic…

Partial Myth: Pupil size is an important factor

 

While having larger pupils doesn’t exclude a person from having LVC there are some important things to know regarding pupil size. The average cornea is around 12 mm wide and 10 mm high. Depending on the specific treatment system, the central 7 to 9 mm of the cornea is reshaped, and the largest change occurs in the central 6 to 8 mm, which is called the optical zone. If you have 8 mm or larger pupils in the dark, your area of vision may extend into or even potentially beyond the “blend zone” of treatment: the transition between the significantly reshaped cornea and your untreated cornea. Modern treatments produce a smooth blend zone which minimizes light scatter, or glare, for most normal pupil sizes, but for a large enough pupil that may not be enough.  This could mean that a point source of light in the dark, like a headlight on the night time horizon, will show a halo or flare coming from it.

What do people really feel after LASIK?

Partial Myth: LASIK causes dry eye

 

Fact: Any form of LVC causes temporary changes to the nerves of the cornea, and LASIK specifically cuts through these nerves. The nerves regrow over around 6 months after the procedure, but in the meantime, this produces a temporary decrease in signals sent from teh cornea to the brain. This is called a “mild neurotrophic cornea” and causes decreased triggers to blink.  The result, which almost everyone experiences after the procedure, is a dry eye feeling which is treated with many of the same approaches used for the medical condition of typical dry eye, but it’s not the same thing.  The self-limited feelings after LASIK that almost everyone experiences, but very few people experience long term, are better called  “transient ocular discomfort”, NOT dry eye.”

 In two FDA-sponsored studies, PROWL-1 and PROWL-2, mild dry eye was reported by about 1 in 4 patients at three months after surgery; the rate of moderate dry eye was 2% to 3%, and the rate of severe dry eye was 1% to 3%. By the six month mark, however, there was a significant reduction in dry eye symptoms. In fact, while 30% of patients noted new dry eye symptoms around 3 months, by the end of the study, nearly 60% reported decreased dry eye compared to before LASIK. [13]

There can be long term dry eye after LASIK, but this is rare.  Typically, this can be readily managed with a wide variety of approaches, including artificial tear drops, punctal plugs, medications like Restasis and Xiidra, and more.  Appropriate and timely diagnosis is very important, because dry eye must be differentiated from neuropathic pain, which is discussed further below under the category of serious potential complications.

The real truth about LASIK and dry eye is that, for the vast majority of people, LASIK produces eyes that feel more comfortable on a day to day basis than longterm contact lens wear.[14]

What are the serious possible complications, and how likely are they?

Myth: Discomfort after LVC is always dry eye

 

        Fact: A rare but serious source of chronic pain after LVC is neuropathic pain (NP).  The exact causes of NP are not yet understood, but the end result is that the nerves which give sensation to the cornea become hyper-sensitive and lead to an experience of pain from what normally would be very mild sensations or even from no stimulation at all.  It can occur after any eye surgery (including LASIK, PRK, SMILE, and cataract surgery); we might think that it is slightly more likely after LASIK since corneal nerves are cut during the procedure and must regrow, but there isn’t evidence to actually support that possibility. NP can feel a lot like dry eye, so it may be mistaken for it, but a key difference is that it continues even when the eye is well treated for any dryness. Neuropathic pain wasn’t recognized at all in the early days of LVC, which unfortunately means that early cases were undiagnosed.  Awareness is fortunately on the rise, and that especially matters because it can be managed successfully if treated early. Treatments start with removing triggers — including maximally managing any dry eye that may be present — and include medicines which decrease nerve inflammation and pain.  If diagnosis is significantly delayed, the condition may become more chronic as it progresses more centrally, and therefore becomes significantly more challenging to treat.

        The exact incidence of neuropathic pain is unknown.  An internal survey conducted by the Refractive Surgery Alliance found that out of 70 surgeons who had performed 1,000 LVC procedures or more, 21 cases of NP were reported out of approximately 1.5 million procedures, for an incidence of around 1 in 90,000 (0.0011%).[15] On the other hand, Pedram Hamrah, MD, one of the few experts in neuropathic pain, believes the incidence to be closer to 1 in 10,000 (0.01%).

Myth: LASIK is dangerous for active people because the flap can become dislodged

Fact: Flap dislodgement outside the first few days after surgery when the flap is initially healing is so rare that no study to date has documented the incidence of late (more than 1 year) postoperative flap dislocations, but it is well accepted that this is extraordinarily uncommon and always associated with ocular trauma.  However, flap dislodgement or dislocation

Around 75% of modern LASIK is performed with femtosecond laser for flap creation, and these flaps have theoretical advantages in strength over those made with microkeratome technology.  Laser-created flaps typically have a tongue-in-groove edge configuration to help them seal down more tightly and heal more securely.

The most avid recipients of LASIK are active individuals, (eg athletes, military, law enforcement, etc) who are exposed to higher trauma risks than the general population. There is even a celebrated case of a US Navy fighter pilot who had LASIK and had to eject from his aircraft; his LASIK flaps remained completely intact in spite of the severe forces he underwent during ejection.[16]  Additionally, it is well accepted that the vast majority of dislodged LASIK flaps can be successfully repositioned without causing permanent vision changes.  With proper postoperative precautions, flap dislocation should not be a valid concern for individuals considering having LASIK unless they have a reasonable expectation of regular, repeated trauma; for example, mixed martial arts (MMA) fighters may be better suited to PRK or ICL refractive surgery.  

The United States military offers LVC to its personnel, and corrected vision is considered a basic part of combat readiness.  It would be tragic for a soldier to suffer harm because of a lost contact lens or broken glasses in the midst of an operation! As of 2016 PRK was most common in the Army (80% of LVC), whereas it is a nearly even split between PRK and LASIK in the Navy (55% PRK, 45% LASIK).[17] 

Truth: Every surgery, including LVC, includes the risks of infection and inflammation

        Fact: Like any other surgery, complications are possible due to external factors, like bacterial or fungal infection, and internal factors, such as the body having an overly-aggressive healing response and causing scarring.

        Infection is a very rare complication. A combined analysis of 9 studies between 1999 and 2015 comprising 669,630 eyes found an infection rate of 0.05% (5 in 10,000) after LASIK.  Not all eyes which suffer an infection will have any long term problems, as many are successfully treated.  This statistic actually compares very favorably to long term contact lens wear, even using daily contacts, as discussed earlier in this chapter.[18]

Of the various types of inflammation, a specific condition called diffuse lamellar keratitis (DLK) is the most concerning.  This a concern specific to LASIK in which non-infectious inflammation occurs in the space between the LASIK flap and the rest of the cornea.  Some old reports from the early 2000s refer to DLK rates as high as 38%.  This is a case of myths being propagated into the modern era based on historical data, however.   Current studies with modern LASIK put the rate at just under 2% for any type of DLK; most types are mild and resolve quickly with steroid eye drops.[19] With prompt treatment, DLK is  typically be handled without long term impact.

Truth: Keratoconus is a valid concern when considering LVC

Keratoconus is a condition where the cornea is abnormally weak, and this weakness can lead to a loss of the proper shape producing a cone-like shape which can’t focus light as well.  In some cases, the condition is clearly evident at the microscope or on the routine screening exams performed prior to surgery. In others, the condition is milder or even very subtle.  Detecting keratoconus isn’t hard with the right equipment, but predicting the future to know who might develop it later is a challenge for which much sophisticated technology and thought has been applied over the last 25 years.  It matters because, if the cornea were already somewhat weak, reshaping it via LASIK or PRK could ‘push it over the edge’ into developing keratoconus.

There is a treatment for keratoconus, which is called corneal crosslinking (CXL).  CXL is a strengthening procedure. It can halt the progression of keratoconus and stop further vision loss. Currently there are investigational studies underway to test whether a patient with keratoconus can have the cornea strengthened and then later safely reshaped via PRK; published results on this approach are very promising.  When the laser is programmed in a specific way, called topography guided, PRK can even account for some or all of the keratoconus’s shape change, potentially restoring better vision.

One of the most important steps of an LVC consultation is a type of corneal scan called ‘tomography’ which looks at the front curve, back curve, power distribution, and thickness distribution of the cornea. This scan will allow your doctor to determine whether your cornea may show signs of keratoconus and whether or not LVC is the best visual option for you. There is a genetic test which can help look for certain genetic markers of keratoconus if desired, and new approaches are under constant development to seek the all-important answer of “is this person’s eye safe for treatment?”  An internal survey of the Refractive Surgery Alliance suggested that this concern was the most common reason to tell someone who came in for a consultation that they weren’t a good candidate for LASIK.  Good surgeons are willing to say ‘no’ and to offer alternatives. The other piece of good news is that we do have the tools to make great judgements with today’s technology and knowledge, especially when used in combination; for example, the Belin/Ambrósio Enhanced Ectasia Display which is one of a few most-common screening approaches that can correctly and automatically identify 99% of keratoconus.[20]


[1] PROWL-1 study

[2] Solomon KD. Modern LASIK outcomes: A review. Presented at: American Academy of Ophthalmology annual meeting; Oct. 14-18, 2016; Chicago.

[3] http://everywakingminute.com/lasikmyth1/

[4] http://everywakingminute.com/lasikmyth2/

[5] https://www.gaeyepartners.com/blog/doctor-editorials/why-i-chose-lasik/

[6] http://everywakingminute.com/lasikmyth1/

[7] PROWL-1 study

[8] Solomon KD. Modern LASIK outcomes: A review. Presented at: American Academy of Ophthalmology annual meeting; Oct. 14-18, 2016; Chicago.

[9] http://everywakingminute.com/lasikmyth2/ – “LASIK vs Contact Lenses”

[10] Masters J, Kocak M, Waite A. Risk for microbial keratitis: Comparative metaanalysis of contact lens wearers and post-laser in situ keratomileusis patients. Journal of Cataract & Refractive Surgery. 2017;43(1):67–73. doi:10.1016/j.jcrs.2016.10.022. https://www.ncbi.nlm.nih.gov/pubmed/28317680

[11] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5221655/

[12] http://everywakingminute.com/lasikmyth3/

[13] http://everywakingminute.com/lasikmyth6/

[14] http://everywakingminute.com/lasikmyth2/ – “LASIK vs Contact Lenses”

[15]Refractive Surgery Alliance Survey on Corneal Neuropathic Pain,  2018

[16] http://everywakingminute.com/lasikmyth17/

[17] https://www.aao.org/eyenet/article/military-members-turn-to-refractive-surgery-to-imp-2

[18] https://www.ncbi.nlm.nih.gov/pubmed/28317680

[19] https://www.ncbi.nlm.nih.gov/pubmed/29923860

[20] Villavicencio OF, Gilani F, Henriquez MA, Izquierdo L Jr, Ambrósio RR Jr, Belin MW. Independent Population Validation of the Belin/Ambrósio Enhanced Ectasia Display: Implications for Keratoconus Studies and Screening. Int J Kerat Ect Cor Dis 2014;3(1):1-8.

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