Corneal laser refractive surgery
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What is corneal laser refractive surgery?
We talk about corneal laser refractive surgery when we are referring to the group of surgical techniques that use a laser to modify the curvature of the cornea and correct refractive errors of the eye (myopia, hypermetropia and astigmatism) and thus eliminate, or at least reduce, the patient’s dependence on glasses and/or contact lenses.
Because of its reliability and safety, refractive laser surgery is the most commonly used method for correcting mild and moderate refractive defects.
Refractive errors
Astigmatism
Astigmatism is characterised by the fact that the eye is unable to form a clean image of an object because the power of the optical system varies between the highest and lowest degrees of power.
Hypermetropia
In hypermetropia, objects in the distance are focused behind the retina, this makes close objects look blurred.
Myopia
Myopia is a change in refraction whereby objects in the distance are focused in front of the retina and not on it, causing blurred farsight.
Surgical techniques (PRK, LASIK, SMILE)
PRK (Photorefractive Keratectomy)
- Laser can be applied directly to the corneal epithelium. To a large extent, it respects the cornea's architecture and physiology, as it acts in a superficial way.
- It is a quick procedure performed all at once.
- It causes pain for a few days and visual recovery is slow.
- Indicated in patients with fine corneas and also in those who, because of their profession or hobbies, may receive impacts to the eyes.
LASIK (Laser-Assisted in Situ Keratomileusis)
- To avoid a lesion to the epithelium, a fine flap is lifted, the laser is applied to the interior (also known as the corneal stroma) and the flap is put back in position.
- Irritation is minimum and vision is quite good the next day.
- Treatment is performed in two sessions, with a break of a few minutes between each one. It ends up having a deeper effect on the cornea and may affect the architecture and corneal nerves.
SMILE (Small Incision Lenticule Extraction)
- It modifies the curvature of the cornea by cutting out an internal lenticule that is extracted using a very small incision.
- The epithelium remains intact, meaning that post-operative pain is almost inexistent.
- The superficial layers remain intact and the corneal nerves are affected to a lesser degree, the risk of ectasia and dryness is low.
- It is performed all at once.
- It is largely dependent on the surgeon's skill and vision is recovered somewhat slower than in the case of LASIK.
It is important to conclude that there are neither better or worse techniques in this field, given that the most important factor is to determine which technique best suits each patient. A proper diagnosis is key.
Practical aspects of the procedure
The pre-operative period
- In the first visit, your current prescription and the state of your eye health will be assessed. An examination will be carried out to determine the main parameters of the cornea.
- Depending on the results, the most advisable type of operation will be determined in each individual case: superficial laser surgery (PRK), laser lenticule extraction surgery using a small incision (SMILE) and intrastromal laser surgery (LASIK).
- The patient should stop using contact lenses at least 15 days before the operation.
- The day before the operation, a series of complementary tests will be performed to confirm the previous data and determine suitable treatment parameters.
The operation
- It is an outpatients surgery, although the patient will have to remain in the clinic for a few hours.
- Anaesthetic drops are applied before the operation.