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Laser Eye Surgery Guide to SMILE vs LASIK vs PRK/LASEK

Despite a seemingly endless list of laser eye surgery treatments to choose from, there are actually only three main types you need to know: SMILE, LASIK, and PRK/LASEK.

We believe that the best treatment should be available for everyone and included in the standard cost of the treatment. But, unfortunately, some laser eye surgery clinics see it as a way to charge more — a bit like optional extras.

Treatments such as UltraLASIK, Accu-wave LASIK, Custom LASIK, UltraLASIKplus, Zyoptix and Wavefront LASIK are brand names that clinics think up in an attempt to differentiate what is effectively the same, albeit packaged slightly differently, treatment – often by taking a treatment such as LASIK and then offering a technology, such as a wavefront measurement, as an optional extra.

If underneath it all there are only three main types of laser eye treatments (excluding PRESBYOND® Laser Blended Vision), then what’s the difference between them?

No matter the type of treatment, Laser Eye Surgery works in pretty much the same way. It uses lasers to reshape the tissue, or stroma, that makes up the body of the cornea, the front window of the eye.

By doing so, it makes the cornea either steeper or flatter depending on the prescription treated, allowing it to bend and focus light more accurately onto the retina and eliminate refractive errors such as shortsighted (myopia) and longsightedness (hyperopia).

Mr Glenn Carp explains

The epithelium is the eye’s invisible barrier to the elements that prevent bacteria and debris from entering the eye. It is incredibly strong, incredibly thin, and possesses the ability to re-populate every 7 to 14 days. For laser eye surgery to work, the epithelium needs to be removed or lifted out of the way to expose the stromal tissue. How this is done is the distinguishing factor between the treatment types.

The Main Difference Between SMILE, LASIK, and PRK/LASEK Laser Eye Surgery

In PRK, the epithelium is completely removed. The laser eye surgeon is then able to reshape the permanent layer underneath. Following this, a contact lens is applied as a bandage to allow the epithelium to re-grow underneath the contact lens and re-populate the eye’s surface.

LASEK also involves removing the epithelium, but rather than being discarded, it is simply temporarily pushed to one side. The permanent layer underneath is then reshaped, and the epithelium is moved back. A contact lens is again applied to the surface to protect it while the new layer re-populates underneath.

LASIK, unlike PRK/LASEK, is not a surface treatment but works by creating a thin flap with a laser that includes the epithelium and a small part of the stroma, the permanent tissue. This allows the surgeon a doorway for reshaping the permanent layer, and as the flap is replaced afterwards. No contact lens is needed, and only the flap edges have to seal over.

If LASIK creates a doorway in the epithelium, SMILE creates a keyhole by creating a tiny connected tunnel from the surface, through the epithelium and down to where the target tissue can be removed. Thus, there is little disruption to the epithelium, and the eye begins to heal almost immediately.

Let’s take a look at the pros and cons of each.

ReLEx SMILE: A Revolution in Laser Eye Treatments

“Generally speaking, traditional Laser Eye Surgery can only correct prescriptions up to a maximum of between -8 and -10… With ReLEx Laser Eye Surgery treatment at London Vision Clinic, people with thin corneas and those with prescriptions of higher than -10 can be treated, because we do not make a flap from the corneal surface.” — Prof Dan Reinstein

ReLEx (refractive lenticule extraction) SMILE (small incision lenticule extraction) is the most up to date approach in laser eye surgery. Introduced in 2011, the procedure is minimally invasive and completely ‘flapless’, involving nothing more than a tiny keyhole incision made in the cornea.

SMILE can do this thanks to the state-of-the-art Carl Zeiss VisuMax laser, which is used to perform the procedure from start to finish. The VisuMax is the only femtosecond laser with the precision to perform SMILE. It is also the laser with the lowest increase in pressure in the eye; the patient feels nothing during the procedure. With guidance from advanced 3D placement, the laser places a series of pulses within the cornea, forming bubbles less than 1/1000th the width of a human hair, outlining the tissue that needs removing, and creating a tiny connecting tunnel through which it can be drawn out.

Whilst sounding very complex, the entire process takes less than four minutes to perform.

The treatment is smoother, quicker, and more comfortable. In addition, the healing time is shorter than that of conventional LASIK, the side effects are minimised, and it is suitable for patients with very high prescriptions, drier eyes, and thinner corneas.

The Pros of ReLEx SMILE

Treatment and Recovery time: As the latest treatment, SMILE transforms Laser Eye Surgery into a minimally invasive procedure that can be performed in a matter of minutes. With the tissue being accessed and removed via tiny connecting tunnels in the outer cornea, no significant healing needs to take place.

Safety and Comfort: SMILE takes Laser Eye Surgery to another level of patient comfort. SMILE offers approximately half the amount and duration of dry-eye over the recovery period. It also retains strength in the cornea as a keyhole replaces the flap.

Suitability and High Prescriptions: Due to the keyhole nature of the procedure, many patients who are told they are unsuitable for other treatments may be suitable candidates for SMILE. Many patients are unsuitable for LASIK as they don’t have a thick enough cornea to remove tissue after making a flap. As ReLEx SMILE uses an exact and minuscule hole at the side of the eye, it leaves the front part of the cornea intact, and allows for more demanding prescriptions to be treated.

What do you think are the main advantages of SMILE over LASIK or PRK?
Professor Reinstein says...

Each procedure may offer benefits, but we evaluate this on a patient by patient basis rather than generalise as a whole. In our clinic, all three procedures are charged at the same fee and are spoken about equally when discussing options with a patient. However, as mentioned before, there will always be a reason for me to choose one procedure over another for any particular patient; I do not offer “options” and allow the patient to choose the procedure. It’s all or nothing with only the best option on the table.

The Cons of ReLEx SMILE

Limited Prescriptions: Although it can treat very high prescriptions, at the moment, SMILE is only available for shortsightedness and astigmatism..

Availability: SMILE is only available at a select few clinics in the UK. London Vision Clinic was the first to introduce the procedure in the UK in 2011, as it was developed by our founder Prof Reinstein.

Seen as the ‘latest technology’ procedure, what do you think about SMILE?
Professor Reinstein says...

The reality is that, even in SMILE’s relative infancy compared to LASIK, the results are impressive. SMILE means that clinics are now able to offer procedure best suits their patients adds another tool for refractive surgeons to use to help best serve their patients. With over 1.5 million procedures performed to date, this is proving a great option for many patients.

In fact, we have written a textbook on SMILE, which was released in April 2018 which has many chapters dedicated to educating Surgeons on the procedure and busting any myths out there.

LASIK: The Staple of The Laser Eye Surgery World

“There are essentially two groups of Laser Eye Surgery treatments. LASIK involves creating a flap in the cornea, and there are surface treatments, which we know are PRK, LASIK, Epi-LASIK etc. The main difference between the groups is the healing time. The results themselves are pretty much the same three months down the line, but it is how you travel, how your journey is in the interim that makes a big difference, and LASIK offers a rapid healing time.” —Mr Glenn Carp

LASIK (Laser-assisted in situ keratomileusis) is not just the most popular Laser Eye Surgery treatment, but one of the most popular elective procedures in the world.

The critical difference between LASIK and PRK/LASEK is that, instead of removing the surface layer of the eye, an ultra-thin hinged flap is created to allow the laser treatment to be made, after which the flap is closed like a door. By returning the flap to its original position in this way, it’s only the edges of the flap which need to heal. Therefore, the recovery time is a fraction of PRK/LASEK, and most LASIK patients are ready to go back to work within 24 hours of surgery.

The Pros of LASIK Laser Eye Surgery

Recovery Time: As the surgeon makes a small flap in the outer layer of the cornea, it’s only the edges of the flap that need to heal, reducing the recovery time.

LASIK can Treat Wavefront: Wavefront error makes up around 5 percent of our vision, accounting for the finer quality aspects beyond common refractive errors such as long-sightedness, short-sightedness, and astigmatism, which are the main focus of glasses and contacts.

The Cons of LASIK Laser Eye Surgery

Treatment Options: The LASIK marketplace is swamped with offers, deals, variations, and added extras. This can make it difficult to know what you’re getting. Choose a clinic with transparent and upfront fees, and be prepared with the questions you need to ask the surgeon.

Safety and Comfort: Patients may experience some irritation and discomfort for up to 24 hours after surgery. However, this is minor and is generally managed with lubricating eye drops.

Minor Side Effects: Patients generally experience a small number of side effects in the 24 hours immediately following the procedure. This can include dry eyes, night vision disturbances, starbursts, and halos and are typically minor and easily managed with lubricating eye drops. Dry eye symptoms typically last for 3 to 6 months.

PRK and LASEK: The Grandparents of Laser Eye Surgery

“With PRK we are able to treat all refractive errors. We are able to treat the full range of myopia, astigmatism and long-sighted treatments, hyperopia. However, it is less predictable for hyperopia when compared to short-sightedness, myopia and astigmatism.” —Mr Glenn Carp

PRK (Photo-Refractive Keratectomy) is the original laser vision procedure that surgeons have successfully used to treat hundreds of thousands of patients since the 1980′s.

PRK was the first Laser Eye Surgery treatment to use the excimer laser, an ultra-precise alternative to traditional scalpel-based refractive surgery procedures such as Radial Keratotomy (RK), which surgeons rarely perform today. LASEK was introduced as an alternative form of surface ablation, with the hope of reducing postoperative haze, speeding up visual recovery, and decreasing postoperative pain. However, scientific studies have found no evidence for any difference between PRK and LASEK.

Generally, PRK and LASEK should only be used when it’s not possible to use LASIK or SMILE. This is because whilst PRK and LASEK produce good results in correcting a full range of prescriptions, including myopia, hyperopia, presbyopia, and astigmatism, the advantages of LASIK and SMILE make them an all-round more effective and safer procedure.

The Pros of PRK/LASEK Laser Eye Surgery

Better Option for Some: PRK/LASEK is not as common as it used to be. However, some patients can benefit from it if they have co-existing eye issues that may be treated simultaneously as correcting the vision, e.g. scars and loose surface epithelium.

The Cons of PRK/LASEK Laser Eye Surgery

Recovery Time: In PRK/LASEK, rather than creating a small flap to access the tissue underneath like in LASIK, the entire outer layer of the cornea is rolled to one side. As it takes several days for the outer layer to re-populate the eye’s surface, the recovery period is the longest of the three.

Safety and Comfort: Although the treatment itself is pain-free, PRK/LASEK patients are likely to experience discomfort or irritation in the seven days following the procedure. However, this is an expected part of the healing process, and thus some clinics will provide pain relief eye drops.


Choosing the right laser eye treatment can seem a monumental task. Still, when it comes down to it, there are only really three treatments most people need to be aware of — more like two today — and what’s best is if you go to a high-quality clinic, the choice is made much simpler as the best comes at the same price.

The parting message is that the old-timer — PRK/LASEK — has largely been made redundant today but may still be a great option if you’re unsuitable for newer surgeries. LASIK retains the title of most popular and sought-after treatment, but only for the time being. As more clinics are beginning to perform SMILE, a greater number of people are becoming aware of its many benefits, SMILE is gaining traction, and as a result, will likely take the top spot as number one. A total of 2 million SMILE surgeries were completed worldwide by April 2019.

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