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Laser Eye Surgery Guide to PRK/LASEK, LASIK, and SMILE

(Updated for 2024)

Researching Laser Eye Surgery can undoubtedly leave you more confused than you were before. With a seemingly endless list of procedures and acronyms, it’s no surprise that many people give up before they have even begun.

But the truth is, there are only three Laser Eye Surgery procedures you need to know about – PRK/LASEK, LASIK, and SMILE.

While you might come across terms such as UltraLASIK, UltraLASIKplus, Custom LASIK, Accu-Wave LASIK, Wavefront LASIK, and Zyoptix, these actually all refer to the same – albeit packaged slightly differently – Laser Eye Surgery treatment. For example, some clinics take a basic LASIK procedure and offer a technology, such as wavefront measurement, as an optional extra. In. contrast, here at London Vision Clinic, we perform Wavefront LASIK as standard.

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.

But if there are three different types of Laser Eye Surgery procedures, what is the difference between them? In this extensive guide, we’ll tell you everything you need to know about PRK/LASEK, LASIK, and SMILE.

How Does Laser Eye Surgery Work?

The first thing you should know about Laser Eye Surgery is that all procedures are based on the same principle. This principle is that an ultra-precise laser is used to remove tissue from the eye to reshape the cornea.

This changes how light is refracted into the eye, allowing it to be focused more accurately on the retina – the photo-sensitive layer at the back of the eye. This allows surgeons to correct a range of refractive errors, including myopia (short-sightedness), hyperopia (long-sightedness), astigmatism, and presbyopia (ageing eyes).

World-renowned surgeon Mr Glenn Carp explains…

Youtube video link The epithelium – the surface layer of tissue – of the eye is extremely effective at protecting our eyes from potential dangers such as dust, debris, and wind. Yet, while it is incredibly strong, it is also very thin. This means that the cells of the epithelium can completely repopulate 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. What separates the three main types of Laser Eye Surgery is how this is achieved.

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

The Surface Procedures

As our expert surgeon, Mr Glenn Carp, explains in the video above, PRK – photorefractive keratomileusis – is the oldest and most invasive procedure, involving the complete removal of the epithelium. This portion of tissue is then discarded. Once the treatment is complete, a protective contact lens is placed over the exposed area of the eye while the tissue beneath re-grows.

While extremely similar to PRK in that a portion of the epithelium is completely removed (these are known as “surface procedures” or “surface ablation”), in LASEK, the epithelium is replaced once treatment is complete. Again, a contact lens is placed over the treatment area to protect the tissue while it heals.

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.

The Corneal Flap

Unlike PRK and LASEK, LASIK does not involve the complete removal of epithelium; instead, a high-precision laser is used to create a thin flap on the surface of the cornea. This can then be folded back to allow access to the tissue beneath. Following the reshaping of the cornea, the corneal flap can be folded back into the place where it begins to fuse. Due to the fast healing power of the epithelium, a contact lens is not required during recovery from LASIK.

The Keyhole Procedure

Finally, we come to the latest innovation in Laser Eye Surgery – ReLEx SMILE. Also known simply as “SMILE”, this is the least invasive of Laser Eye Surgery procedures.

Avoiding both the removal of epithelium, and the creation of a corneal flap, SMILE works by creating a small hole in the surface tissue of the eye using an incredibly precise laser. This state-of-the-art laser creates a tiny connected tunnel from the surface of the eye through to the corneal tissue. The surgeon can then reshape the cornea, drawing out tissue through this tunnel. Given the minimally invasive nature of the SMILE procedure, the eye begins to heal almost immediately.

So, now that we’ve covered the basics of PRK/LASEK, LASIK, and ReLEx SMILE, 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 modern development in Laser Eye Surgery techniques. Introduced in 2011, SMILE eliminates the need for both surface ablation and the creation of a corneal flap, requiring just a keyhole to perform the procedure. This ‘flapless’ procedure is therefore less invasive than its predecessors.

SMILE is performed using the state-of-the-art Carl Zeiss VisuMax laser. Co-created by our very own Professor Dan Reinstein, this is the only femtosecond laser with the required precision to perform the SMILE procedure. Furthermore, it also limits the amount of pressure in the eye – so the patient feels almost nothing during their treatment!

But, how does it work?

With guidance from advanced 3D placement, the VisuMax laser delivers a series of pulses from the surface of the cornea. These pulses form tiny bubbles (less than 1/1000th the width of a human hair) creating a small tunnel directly to the corneal tissue that needs to be removed. Finally, the removed tissue can be drawn through this tunnel to leave the cornea in its new, corrected shape.

While this might sound very complex, the whole procedure is usually completed in less than four minutes, making it the fastest Laser Eye Surgery procedure to perform.

Youtube video link

The Pros of ReLEx SMILE

Treatment and Recovery time: ReLEx SMILE is an altogether smoother, faster, and more comfortable treatment option. But one of the biggest pros of this technique comes after the procedure itself. Thanks to the minimally invasive nature of SMILE, this procedure offers the fastest healing times of all Laser Eye Surgery treatments. The procedure itself is completed in a matter of minutes while many patients are fully recovered in just a matter of days.

Safety and Comfort: SMILE makes Laser Eye Surgery more comfortable – both during the treatment and afterwards. The severity and duration of common Laser Eye Surgery side effects such as dry eyes can be significantly reduced. The keyhole approach also helps to retain 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 – including those who may have previously been told they are unsuitable for Laser Eye Surgery. This can include patients with very high prescriptions, as SMILE leaves the front part of the cornea intact, allowing for more demanding prescriptions to be treated. Patients with pre-operative dry eyes and thinner corneas are often also good candidates for SMILE.

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

Each procedure has its 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 make Laser Eye Surgery an option for more people – and can be used to treat extremely high prescriptions – it is not suitable for everyone; particularly patients with long-sightedness (hyperopia).

Availability: Due to being one of the most recent innovations in Laser Eye Surgery, 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 Professor Dan 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 commonly performed Laser Eye Surgery procedure. In fact, LASIK is now one of the most popular elective procedures in the world.

The introduction of the corneal flap that characterises LASIK was a huge development that significantly reduced the recovery times associated with Laser Eye Surgery. Thanks to this, the vast majority of patients are now able to return to many of their usual activities in just a matter of days. Many can even return to work after just 24 hours!

Youtube video link

The Pros of LASIK Laser Eye Surgery

Recovery Time: Avoiding the complete removal of epithelium means that there is much less disruption to the surface of the eye. As a result, healing times are significantly faster than those seen with PRK/LASEK

LASIK can Treat Wavefront: Wavefront errors refer to irregularities outside of refractive errors such as long- and short-sightedness, that can also affect our quality of vision. These higher-order aberrations make up around 5 per cent of our vision. While refractive errors can be corrected with visual aids such as glasses and contact lenses, these are not effective for wavefront irregularities. However, Wavefront-guided LASIK can correct many of these errors.

The Cons of LASIK Laser Eye Surgery

Treatment Options: As we mentioned at the start of this guide, the wide availability of LASIK has helped to swamp the marketplace with a huge number of variations and added extras. This can make it difficult to know what you are actually getting – and if it is the best possible option. Always opt for a clinic with transparent and upfront fees, and be prepared with important questions to ask the surgeon.

Safety and Comfort: While LASIK is less invasive than older iterations of the procedure, patients may still 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 and over-the-counter painkillers.

Minor Side Effects: LASIK can be associated with a small number of side effects in the hours immediately following the procedure. This can include dry eyes, night vision disturbances, starbursts, and halos. Again, these side effects are typically mild and are easily managed with lubricating eye drops. Dry eye symptoms typically last for up to 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 oldest of the laser vision procedures. Surgeons have been successfully applying this technique to treat hundreds of thousands of patients since the 1980s.

PRK was the first refractive surgery to apply the excimer laser. Developed as an ultra-precise alternative to traditional blade-based refractive surgery procedures such as Radial Keratotomy (RK), the excimer laser is now used in the vast majority of refractive surgeries today.

LASEK was the next step in the progression of Laser Eye Surgery. As mentioned above, it removed the need for the epithelium of the eye to completely repopulate, as the removed area of tissue could be put back in place after surgery. However, while it was hoped that this would help to reduce post-operative haze, speed up recovery times and improve comfort for patients, scientific studies have found no evidence of any difference between the two procedures.

While PRK/LASEK is still a good option for effectively correcting a full range of refractive errors, these procedures are generally only offered when LASIK or SMILE treatment is not suitable.

The Pros of PRK/LASEK Laser Eye Surgery

Better Option for Some: While PRK/LASEK is not as common as it used to be, some patients may benefit from it if they are not suitable for other treatment options. For example, patients with co-existing eye issues 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: PRK/LASEK are the most invasive forms of Laser Eye Surgery. As a result, the recovery and healing process is significantly longer than those for newer forms of the treatment. It can take around 7-14 days for the affected area of the epithelium to re-populate, making the recovery period for PRK/LASEK the longest of all Laser Eye Surgery procedures.

Safety and Comfort: Although, like all Laser Eye Surgery procedures, PRK/LASEK is generally pain-free, it is common for patients to experience more discomfort in the days following their treatment. However, this is an expected part of the eye’s healing process, and thus many clinics will provide painkillers and pain relief eye drops.


With the overwhelming number of supposedly different options available, choosing the right Laser Eye Surgery treatment can seem like a monumental task. But, when it comes down to it, there are only three options that you need to be aware of.

Furthermore, in reality, the vast majority of patients will be ordered either LASIK or ReLEx SMILE. What’s more, if you opt for one of the higher-quality Laser Eye Surgery clinics, the whole process is made that much simpler as an experienced surgeon will always offer the best option for you at the same price.

For now, LASIK remains the most popular option; however, the new kid on the block may soon take this crown. As ReLEx SMILE becomes more widely available, a greater number of people may soon benefit from its less invasive nature and faster healing times.

Do you have any more questions about PRK/LASEK, LASIK, and SMILE? Don’t hesitate to get in touch with one of our friendly clinic coordinators today – they’re always happy to help! Alternatively, Book your Consultation to start your journey to clearer vision.

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