Does Flap Thickness Matter?

Laser Eye Surgery has now been used to correct vision for over four decades. The procedure has always involved accessing the corneal bed in order to reshape the cornea. But, the thickness of the corneal flap created to access the corneal bed has reduced significantly over the years. Today, there is even a flapless form of Laser Eye Surgery, reducing the invasiveness of the procedure.

This speaks volumes about how flap thickness is related to safety during and recovery following Laser Eye Surgery.

The Reduction Of Flap Thickness

A flap has been used to access the cornea since the introduction of Laser Eye Surgery in the 1980s. In fact, in PRK/LASEK procedures, a whole section of the corneal epithelium (skin) is removed in order to allow access to the corneal bed underneath. As technology and knowledge have evolved, however, surgeons have been able to create smaller and thinner flaps in the cornea.

The creation of thinner flaps helps us to better preserve the structure of the cornea, meaning less discomfort, faster recovery time, and lower risks of haze and dry eye following the procedure.

The use of ultra-precise lasers, as opposed to microkeratomes (used in conventional PRK/LASEK), in the creation of corneal flaps also promotes further postoperative advantages.

To get more of an idea of how flap thickness has played a key role in the progression and modernisation of Laser Eye Surgery, here is a review of our most common procedures: PRK/LASEK, LASIK, and the minimally-invasive ReLEx SMILE.


PRK and LASEK, the first Laser Refractive Surgeries approved by the FDA in 1995, are both classed as surface procedures. As mentioned earlier, these procedures involve the complete removal of the corneal epithelium to allow the reshaping of the cornea. A soft contact lens is applied to the exposed area to aid the regrowth of the epithelium in the days following surgery.


Approved by the FDA in 1999, LASIK introduced a less invasive way to access the corneal bed. LASIK involves the use of a computer-controlled instrument or laser to cut a thin, hinged flap into the cornea. Following the procedure, this flap can then be folded back into place and the cornea can begin to heal. As only a small part of the cornea has been affected, the healing process is far quicker than in PRK/LASEK.


Finally, ReLEx SMILE, the latest innovation in Laser Eye Surgery, has removed the need for a flap altogether. This minimally-invasive procedure, developed by Carl Zeiss with help from London Vision Clinic, instead uses the Carl Zeiss VisuMax laser to deliver a series of pulses to the cornea. These pulses form a number of bubbles (less than 1/100th the width of a human hair) creating a tiny tunnel to the corneal bed – through which the surgeon can draw out tissue to reshape the cornea.

As no flap is created, the procedure takes only a few minutes, post-operative risks are decreased, and the healing time is even faster than conventional LASIK. 

As Professor Dan Reinstein explains:

“Not only is the patient experience greatly enhanced, as there is less surgical manipulation of the eye – making it less invasive than traditional Laser Eye Surgery – but it also makes vision correction available to people who would have previously been told that they were unsuitable candidates. It’s a major development.”

If you would like to find out more about the benefits of ReLEx SMILE surgery, Book a Consultation or give us a call on 020 7224 1005.