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

(Updated for 2023)

Researching Laser Eye Surgery can give the impression that there is an endless list of procedures to choose from; but the truth is, there are only three main types of Laser Eye Surgery you need to know about: SMILE, LASIK, and PRK/LASEK.

At London Vision Clinic, we believe that everyone should have access to the very best Laser Eye Surgery treatment – with no hidden costs or extras. While some Laser Eye Surgery clinics seize every opportunity to charge more, we include everything in our treatment plans, as standard.

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.

Underneath all the smoke and mirrors, though, there are only three main types of Laser Eye Surgery treatments (excluding PRESBYOND® Laser Blended Vision). So, what’s the difference between them?

All kinds of Laser Eye Surgery treatments are based on the same principle. They use lasers to reshape the tissue (or stroma) that makes up the body of the cornea – the window of the eye.

This changes the way that light enters the eye and allows light to focus more accurately onto the retina. In turn, this allows us to eliminate various refractive errors, including short-sightedness (myopia), long-sightedness (hyperopia), and astigmatism.

World-Renowned Surgeon Mr Glenn Carp explains

Youtube video link

The epithelium, the surface layer of tissue, of the eye plays an incredibly important role. It protects our eyes from the elements and potentially harmful debris. While the epithelium is incredibly strong, it is also very thin and as such, has the ability to completely re-populate in just 7-14 days.

The first step in any Laser Eye Surgery procedure is to remove this layer of tissue to allow access to the corneal tissue beneath. The way in which this is done is what distinguishes between the three main types of Laser Eye Surgery.

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

As Mr Glenn Carp explains, PRK is the most invasive procedure, involving the complete removal of the epithelium. Then, once the surgeon has permanently reshaped the tissue underneath, a contact lens is applied over the exposed area of the eye. This protects the eye while allowing the epithelium underneath to re-grow.

Similar to PRK, LASEK also involves the removal of the epithelium (these are known as “surface procedures”). Unlike PRK, however, rather than being discarded, in LASEK the epithelium is temporarily pushed to one side to allow access to the tissue underneath. Once the corneal tissue has been reshaped, the layer of the epithelium is moved back to cover the exposed area of the eye. A contact lens is again applied to protect the eye while it heals.

In contrast, LASIK is not a surface procedure. This means that the layer of the epithelium is not completely removed from the surface of the eye; instead, the surgeon uses a laser to create a thin flap in the epithelium that can then be folded back to reveal access to the corneal tissue. Following the next stage of the procedure, this flap is then folded back. As only the edges of the epithelium now need to heal, a contact lens is not needed.

Finally, we come to ReLEx SMILE, the least invasive of Laser Eye Surgery procedures. This technique works by creating a keyhole in the eye using an incredibly precise state-of-the-art laser. This laser works by creating a tiny connected tunnel from the surface of the eye through to the target tissue. Surgeons can then reshape the cornea, drawing tissue through this tunnel. SMILE involves little disruption to the epithelium, meaning that the eye can 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, SMILE eliminates the need to remove a portion of the epithelium. This ‘flapless’ procedure makes Laser Eye Surgery less invasive than ever before, using only a keyhole to reshape the cornea.

This is done using the state-of-the-art Carl Zeiss VisuMax laser, which is used for the entire procedure. The VisuMax laser, co-created by our very own Professor Dan Reinstein, is the only femtosecond laser with the required precision to perform the SMILE procedure. Furthermore, it also creates the least amount of pressure in the eye – so the patient feels almost nothing!

So, how does it work? With guidance from advanced 3D placement, the VisuMax laser delivers a series of pulses into the cornea. These pulses form tiny bubbles (less than 1/1000th the width of a human hair) that outline the tissue that needs to be removed and create a tiny tunnel through which the tissue can be drawn out.

While this might sound very complex, the whole procedure is usually completed in less than four minutes.

Youtube video link

ReLEx SMILE treatment is a smoother, faster and more comfortable procedure. Yet one of the biggest pros comes after the procedure itself. The minimally invasive nature of SMILE means the healing times are significantly faster than those of earlier forms of Laser Eye Surgery. It also means that the side effects are minimised and treatment is suitable for more people than ever before – including those with very high prescriptions, drier eyes, and thinner corneas.

The Pros of ReLEx SMILE

Treatment and Recovery time: SMILE transforms Laser Eye Surgery into a minimally invasive procedure with faster treatment and recovery times. The procedure itself is completed in a matter of minutes while many patients are fully recovered in just a number of days.

Safety and Comfort: SMILE makes Laser Eye Surgery more comfortable – both during the treatment and afterwards. Dry eyes are a common side effect of Laser Eye Surgery, but with SMILE both the duration and the severity of dryness are approximately halved. The keyhole approach also retains the strength of the cornea.

Suitability and High Prescriptions: This minimally invasive procedure opens the possibility of clearer vision to more people than ever before – even those who have previously been told they are unsuitable for treatment. Many patients who are unsuitable for other Laser Eye Surgery treatments are suitable candidates for SMILE. As SMILE leaves the front part of the cornea intact, it 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 has its own benefits, but we evaluate the suitability of each treatment on a patient-by-patient basis. At London Vision Clinic, all three procedures are charged at the same rate and are all discussed openly with our patients. 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: While SMILE can treat extremely high prescriptions, it can currently only be used to treat patients with short-sightedness or astigmatism…

Availability: ReLEx SMILE treatment is currently only available at a select few clinics in the UK. London Vision Clinic was the first clinic in the UK to offer this innovative treatment, as it was co-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 procedures that best suit their patients and add 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, with 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 the most popular option for Laser Eye Surgery. More than this though, it is also one of the most popular elective procedures in the world.

As we touched on earlier, the main difference between LASIK and PRK/LASEK is that, rather than removing the surface layer of the eye, the surgeon creates a flap in the epithelium. After the next stage of the treatment, this flap is closed, once again covering the exposed area of the eye. This means that only the edges of the flap need to heal. As a result, the recovery time following LASIK is a fraction of that of PRK/LASEK. In fact, most LASIK patients are able to head back to work within 24 hours of the surgery.

Youtube video link

The Pros of LASIK Laser Eye Surgery

Recovery Time: Less disruption to the surface of the eye (compared with LASEK/PRK) means that healing times are much faster.

LASIK can Treat Wavefront: Wavefront error makes up around 5 per cent of our vision. It accounts 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: As LASIK is the most popular – and hence, most widely available – Laser Eye Surgery procedure, the marketplace is swamped with ‘offers’, ‘deals’, variations, and added extras. This can make it more difficult to know exactly what you are getting. Always opt for a clinic with transparent and upfront fees, and be prepared with important questions to ask the surgeon.

Safety and Comfort: Patients may experience some irritation and discomfort for up to 24 hours after surgery. However, this is usually mild 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. These side effects are typically mild and are 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. Surgeons have successfully used the procedure to treat hundreds of thousands of patients since the 1980s.

PRK was the first Laser Eye Surgery treatment to use the excimer laser. The laser was developed as an ultra-precise alternative to traditional blade-based refractive surgery procedures such as Radial Keratotomy (RK). Thanks to this development, the vast majority of refractive surgeries today are completely bladeless.

LASEK was the next development in Laser Eye Surgery. It was developed to offer an alternative to surface ablation procedures (complete removal of an area of the epithelium). It was hoped that this procedure would reduce post-operative haze, speed up recovery times and improve comfort for patients. However, scientific studies have found no evidence of any difference between the two procedures.

Generally, PRK and LASEK are only used when LASIK or SMILE treatment is not appropriate. While PRK/LASEK still produce good results in correcting a full range of prescriptions (including myopia, hyperopia, presbyopia, and astigmatism), the advantages of newer techniques make LASIK and SMILE an all-around more effective and safer option.

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 are not suitable for other treatment options. For example, patients with 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: The more invasive nature of PRK/LASEK means that more time is needed for the eye to heal completely. It can take several days before the affected area of the epithelium has re-populated, making the recovery period for PRK/LASEK the longest of all Laser Eye Surgery procedures.

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.


With all the apparent options available, choosing the right Laser Eye Surgery treatment can seem like a monumental task. But it doesn’t have to be this way. When it comes down to it, there are only really three treatments that most people need to be aware of. In fact, the vast majority of people will be offered either LASIK or ReLEx SMILE. What’s more, if you go to a high-quality clinic, the choice will be made much simpler as the best option for you will always cost the same.

While the old-time – PRK/LASEK – has largely been made redundant today, it may be the better option in some cases. For now, LASIK remains the most popular option; however, it is likely that the new kid on the block will soon take this crown. As SMILE becomes available at more clinics, a greater number of people are becoming aware of its many benefits. SMILE is certainly 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.

Have more questions? Get in touch with one of our friendly clinic coordinators today – they will be happy to help. Alternatively, Book your Consultation to start your journey to clearer vision.

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