Refractive surgery

Modern lasers are better in speed and accuracy than older ones, so results are far superior than the early years of refractive surgery (1990-2000). We currently use the state-of-the-art Concerto (Wavelight) excimer laser, which is one of the fastest and most modern laser available worldwide. With high frequency (500Hz) and excellent eye-movement tracker, it has unparalleled results even in high amounts of refractive errors.

What are refractive errors?

    In myopia (short-sightness), incoming rays of light are focused in front of the retina (the sensitive layer inside the eye like the film in the camera), resulting in dim vision for distance without glasses or contact lenses. In hyperopia (long-sightness), incoming rays of light are focused behind the retina, resulting in dim vision for near and frequently for distance, depending on the amount of error. In astigmatism the cornea (the surface transparent layer of the eye) has unequal curvatures (instead of being like a football, it rather has the form of a rugby ball) resulting in dim vision in all distances. In all kinds of laser refractive surgery, the excimer laser is used to reshape the surface of the eye (the cornea), in order to eliminate any refractive error, so that vision is clear without glasses or contact lenses.

There are three main conditions to be met if you are considering refractive surgery:

  1. Your refraction (your prescription): Refractive surgery has good results up to 12 dioptres of myopia, up to 6 dioptres of astigmatism and up to 4 dioptres of hyperopia (depending on cornea thickness).
  2. The shape and thickness of the cornea: In some cases the shape of the cornea is abnormal (e.g. keratoconus) and refractive surgery is contraindicated. The same applies in cases where the cornea is very thin. Preoperative tests (cornea topography and pachymetry) are carried on all candidates. If you are a contact lens user, it’s important not to wear your lenses before these tests, because the shape of the cornea is affected.
  3. Your age: You must be over 18 years of age and have stable refraction for at least a year.


Which are the options in laser refractive surgery? 

In ASA (advanced surface ablation) the surgery is carried on the surface of the cornea. Initially the superficial layer (epithelium) is removed without any cutting (rather lifting) and then the laser is applied. The main difference between ASA and LASIK is that in ASA there is no cut on the cornea but the refractive laser is the same. Problems previously related with surface techniques (regression, haze, pain) are usually no longer an issue with advanced surface ablation.

 In LASIK (laser in situ keratomileusis) the surgery is carried on approximately in 1/4 the depth of the cornea. Initially a femtosecond laser cuts a thin superficial flap (like a laser blade). Then the flap is lifted and the excimer laser is applied on the cornea. The thin flap is repositioned at the end of the treatment and stays in place without any sutures.

The choice of the method of refractive surgery depends on the amount of the refractive error, the thickness of the cornea and personal preference. In LASIK there is faster visual rehabilitation and less pain, whereas in ASA there is some pain for the first two days and fluctuation of vision for a few days, mainly because of the time for the surface to heal (a special contact lens is used for three days). On the other hand in ASA there is no cut on the cornea. Eventually both techniques have comparable long term results as shown in large studies. Dr George Kampougeris will discuss the appropriate technique for you during your consultation.


In monovision one eye is corrected to zero and the other is left slightly myopic in purpose (-1 or -1.5). Thus the brain subconsciously uses one eye for distance and the other eye for near (the low myopic eye). It is a good choice for people who dislike wearing presbyopic glasses after the age of 45. Not all people are suitable for monovision. There is a special test for monovision success, which will be done during your consultation.

G. Kampougeris, MD, MRCSEd (Ophth), PhD Consultant Ophthalmic Surgeon, x Consultant, Moorfields Eye Hospital NHS Trust

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