Since the middle of the 20th century, surgical procedures have been researched and perfected in order to improve the quality of life of people who need to wear glasses or contact lenses to correct their visual defects.
The objective of refractive surgery is to modify the radius of curvature of the cornea, flattening it in myopia and curving it in hyperopia, in order to focus images sharply on the retina. Nowadays this is achieved thanks to the excimer laser that produces a photoablation of the corneal stroma in relation to the power of the refractive defect.
Indications prior to laser refractive surgery
It is a prerequisite to operate any refractive defect that the patient is over 21 years old and the refractive defect has been stabilized for about two years, especially in the case of myopia.
The preoperative examination to evaluate if the patient is a candidate for surgery requires that the patient has withdrawn the use of contact lenses, if he/she is a contact lens user, 15 days before the examination.
a) Myopia: Taking into account that in this case the objective is to flatten the cornea, the laser should reduce its thickness, never exceeding 400 microns of corneal thickness. Therefore, if the patient has a thin cornea or a high myopic power, it is possible that the laser intervention cannot be performed. In general, myopia of up to 7-8 diopters can be treated with laser depending on the above.
b) Hyperopia: The laser in hyperopia acts by curving the cornea. Therefore, the thickness of the cornea does not have as much influence as in the case of myopia. However, it has been proven that both the quality of vision and the limit of diopters that can be treated with laser should not exceed 4-5 diopters. Visual recovery is somewhat slower than in myopia.
c) Astigmatism: Astigmatism correction can be performed both in pure cases and in cases associated with any of the above mentioned defects.
Laser refractive surgery: intervention
It is an outpatient procedure that is performed monocularly or bilaterally in the same surgical act under local anesthesia, ie by instilling anesthetic drops on the surface of the eye only, associated with a tranquilizer orally if the patient’s state of anxiety requires it. The surgery is absolutely painless.
Using a microkeratome or a femtosecond laser, a thin layer of the cornea is separated and the laser is then applied to the corneal stroma. The corneal flap is then replaced without suturing and the procedure is completed. The procedure lasts approximately 5 minutes per eye.
The patient leaves the clinic after a few minutes and can lead a normal life after a few hours, although the final vision is not stabilized until 1-3 days after surgery.
Although complications have been described, they are exceptional with current technology and their incidence is minimal.
The aseptic measures and antibiotic coverage make infections almost impossible.
Follow-up after laser refractive surgery
The patient will be able to lead a normal life a few hours after the operation, although he/she should avoid crowded environments (especially smoke) and should not drive until his/her vision allows it (between 24-48 hours). Also (and most importantly) you should not rub your eyes for the first 15 days and you should use antibiotic and anti-inflammatory drops for a few days. As this procedure produces a certain degree of dryness at the beginning, it will also be necessary to instill artificial tears for about two months.
During the first few days some degree of “fogging” may occur exceptionally at night, which disappears after a few days. It is more frequent in high defects.
The definitive result must be evaluated after 6 months and if exceptionally a small residual defect remains, it can be operated again without problems.