Corneal refractive surgery aims at changing corneal power to "incorporate" vision correction into the eye.
This is achieved through a change in shape from "flattening" the radius of curvature for myopia to the creation of a central bulge in cases of hyperopia. In both cases, the procedure can integrate astigmatism treatment by modifying the treatment on a meridian.
There are two main methods of laser treatment:
PKR or Photorefractive keratectomy:
The Excimer laser in this technique is applied directly to the surface of the cornea, at the Bowman membrane.
The epithelium is previously removed from the treatment area.
LASEK and EpiLASIK are variants of this technique.
Here, the Excimer laser is delivered after preparing a corneal flap. The flap is a fine strip of surface corneal stroma (of about 90 to 120 microns).
For All laser LASIK, also called FEMTOLASIK or ULTRALASIK, the flap cutting is done using a Femtosecond laser, which ensures safety and reproducibility.
With the old standard Lasik, the flap was cut with an automated machine, called a microkeratome. It was an oscillating and very fine blade. Its use is now very rare in modern centres equipped with Femtosecond technology, which has advantageously replaced it.
How to choose the technique?
Your surgeon will offer you one of the methods depending on your test results.
Usually, both eyes are treated on the same day.
However, some general medical principles usually apply:
- Low myopia can be treated either by Femtolasik or PKR.
- A significant degree of myopia is managed using a Femtolasik type treatment.
- Isolated astigmatism or associated with another refractive disorder is managed using a Femtolasik type treatment.
- Treatment of hyperopia with or without associated astigmatism is managed with a Femtolasik type treatment.
- Treatment of presbyopia (except small associated myopia) is managed with a Femtolasik type treatment.
- Overall, PKR treatment is more painful and longer in terms of visual recovery than Femtolasik treatment,
- With PKR treatment, you can resume sports that involve a potential risk of injury to the eyes, faster than with Femtolasik.
- PKR treatment reduces the benefit waiting period for certain professions (firefighter, military...).
Surface treatment by PKR:
It is very simple in the absence of corneal flap cutting. The visual results are very good for small visual defects, although there may be transient discomfort and postoperative pain in the first 48 to 72 hours. Recovery is slow, over several days, but the eye heals quickly from a mechanical point of view and has no particular risk in case of trauma.
There is eye sensitivity to UVs in the first year and wearing sunglasses is required for one year when exposed to the sun. Strong visual defects are not accessible to this treatment due to risks of healing problems (haze) and/or regression of the treatment.
Today, it accounts for over 90 % of patients' choice.
Visual recovery is extremely fast (24-48 hours). There is almost no postoperative pain and you may resume work after a few hours in the absence of corneal traumatic risk. If the cornea is thick enough, treatment can be offered regardless of the initial refractive disorder. However, this technique has specific risks related to the cutting of the flap, but today they are minimal with the introduction of the Femtosecond laser.
Each case is a specific personal situation, and as always in medicine, your surgeon, will be able to discuss this with you in order to provide the therapeutic solution most suited to your needs and your case.