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A patient's guide to eye surgery sponsored by the London Eye Hospital

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London Eye Hospital, a dedicated ophthalmic hospital treating all eye conditions, with state-of-the-art facilities in Harley Street and Wimpole Street.
Eye surgery

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Laser eye surgery guide

Laser eye surgery

One of the most common types of eye surgery done all over the world today is laser surgery to correct common eyesight defects. Short sight (myopia), long sight (hyperopia) and astigmatism can all be improved by using a laser to change the shape of the cornea. This allows light to focus directly on the retina, rather than in front of, or behind it.

The first type of laser eye surgery developed for visual correction was PRK – photorefractive keractectomy.

What is PRK?

Photorefractive keractectomy can be a permanent solution to eyesight defects. The laser techniques involved were developed during the 1970s and 1980s but PRK as a form of surgery was not approved until 1995. Since then, probably millions of PRK procedures have taken place.

During PRK, the eye surgeon removes the surface layer of the cornea using alcohol or a physical technique to scrape away the cells. This reveals the layers of the cornea that can be modified by the laser.

Today, complex 3D mapping techniques using scanning and computer technology produce a contour map of each individual cornea so that the surgeon can use the laser with great accuracy and precision.

Afterwards, a disposable contact lens is placed over the eye to protect it until new cells grow to replace the outer layer removed at the start of surgery.

Disadvantages of PRK

Healing can take a few days and people often find those days quite uncomfortable. For some people, PRK is still the ideal solution and this type of laser eye surgery is still used. It has been superceded to some extent by newer techniques.


LASEK is a variation of PRK. The acronym stands for laser-assisted sub-epithelial keratectomy.

LASEK differs from PRK because the surface layer of the cornea is not destroyed either chemically or physically at the start of surgery. It is gently pushed out of the way and then put back onto the cornea after reshaping with the laser is complete. The cells within the surface layer don’t survive, but placing them over the sculpted cornea is easier on the eye during the few days in which a new surface layer grows.

As the technique is damaging to the cornea, recovery can be faster. People report less pain in their eyes after surgery, clearer vision with no haze and less time to having improved vision.

LASEK has been used successfully on probably hundreds of thousands of people in the world but it is currently less popular than the newer LASIK technique.


LASIK was developed at the end of the 1990s. The surface layer of the cornea is not removed or scraped away, or pushed to one side. Removal is done very precisely using microsurgery to create a flap, which remains attached at one side.

The laser is then used to make the required shape changes to the cornea underneath, and then the flap is closed. The eye then recovers with its surface layer in tact.

As you would expect, recovery is much faster and easier than after PRK or LASEK. When the flap of tissue is laid back over the cornea, surface tension sucks it into place and cell regenerate at the edges of the flap, usually within a few hours.

Combination laser eye surgery

The different techniques have their own subtle variations and successful laser eye surgery often depends on the skill of the surgeon in matching the patient with the most suitable technique for them, not just in his or her skill in the operating theatre.

Techniques are also evolving and people who have very severe sight problems, abnormal corneas or other complications may be treatable using a combination of laser surgery and lens implants. Bioptics is a new area of ophthalmology that could expand a great deal in the next few years.

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