LASer In situ Keratomileúsis (Lasik)
What is it?
It is an eye surgery, performed using an Excimer Laser (an ultraviolet laser), in which the shape of the cornea is permanently molded to correct refractive errors.
To perform the procedure, a corneal tissue flap is created. This flap is then detached so that the Excimer Laser can reshape the underlying corneal tissue.
Indications
Not all patients are candidates for this type of surgery. For undergoing LASIK surgery, you must meet certain requirements. Among them, it is worth highlighting:
· Patient must be 18 years or older (ideally, you should be over 21 years of age, which is when your vision is most likely to have stable).
· Optical correction (graduation) must not have changed in the last year.
· You must have a refractive error that can be treated with LASIK. In general terms (although it depends largely on the characteristics of each case) it could be said that the limit is 4 diopters for astigmatism, 5 diopters for hyperopia, and 7 diopters for myopia.
· The cornea must have a “minimum” thickness to be able to perform the surgery successfully and it must be healthy.
· You must have realistic expectations about what LASIK can or cannot achieve for each particular case.
People considered as not “suitable” for LASIK are those who present the following:
· An unstable or changing refractive error in the last year.
· A refractive defect that exceeds the corrective ability of LASIK.
· Dry eye.
· Corneas with insufficient thickness (too thin) for the defect to be corrected.
· Corneal pathologies, such as, for example, keratoconus, chemical burns, scars.
· Other ophthalmological pathologies, such as glaucoma, ocular diabetes.
· Pregnant and / or lactating women, since vision is unstable.
LASIK is an outpatient procedure that is performed under topical anesthesia.
Most people will be able to do most of their daily activities without corrective lenses, although they may need glasses for certain activities, such as reading.
Before performing LASIK surgery, the patient will undergo a standard ophthalmological examination to detect any problem that could contraindicate it.
In addition, it is essential to have a preoperative record, since the ophthalmologist may need this information to perform other processes, such as cataract surgery or pathologies, such as glaucoma.
Femtosecond laser
What is it?
It is the most accurate laser that currently exists to perform refractive surgery. It uses infrared light in very short pulses (they are measured in femtoseconds, that is, one billionth of a second). The incision made with the femtosecond laser is minimal, it reproduces with great accuracy the microincisions previously designed by the surgeon, which means little impact on the corneal cells.
In what cases is it used?
In addition to refractive surgery, the femtosecond laser can be used for corneal surgeries, such as keratoconus or corneal transplantation. It can also be used for cataract surgery and correction of presbyopia.
Candidate patients to benefit from refractive surgery with a femtosecond laser are:
· Patients with a high refractive error (myopia, hyperopia, and / or astigmatism).
· Patients with thin and / or irregular corneas.
· Patients with dry eye.
· Patients with unstable vision.
Surgical technique
The Relex Smile technique is the most modern method for the treatment of refractive errors. A 2mm micro incision is made, which preserves the corneal structure and reduces potential risks. This technique involves applying the laser directly inside the eye and avoids cutting the most superficial layers, as is done with other older techniques.
Although it is a very safe technique, it is not without complications, such as the incidence of corneal aberrations. The possibility of complications is more related to the individual characteristics of each patient than to the technique itself.
On the other hand, with this technique it is not possible to perform retreatment.
Femtosecond laser in combination with Excimer laser
What is it?
The FEMTOLASIK is the realization of a LASer In situ Keratomileúsis with a femtosecond laser. This procedure uses two types of lasers:
· Femtosecond laser: Used to make the initial cut in the cornea, allowing greater precision.
· Excimer laser: used to correct the refractive defect.
This technique allows correcting myopia of up to 8 diopters; astigmatisms of approximately 6 diopters, and hyperopias between 4.5-5.5 diopters safely and effectively.
In which patients can it be used?
This technique can be used in all those patients who are candidates for refractive surgery using LASIK.
· Patients with refractive errors of:
o Hyperopia: up to 5.5 diopters.
o Astigmatism: up to 6 diopters.
o Myopia: Up to 8 diopters.
· Patient must be 18 years or older (ideally, you should be over 21 years of age, which is when your vision is most likely to have stable).
· Optical correction (graduation) must not have changed in the last year.
· The cornea must have a “minimum” thickness to be able to perform the surgery successfully and it must be healthy.
· You must have realistic expectations about what FEMTOLASIK can or cannot achieve for each particular case.
Similarly, non-LASIK-fit people are considered FEMTOLASIK unfit, such as:
· An unstable or changing refractive error in the last year.
· A refractive defect that exceeds the corrective ability of LASIK.
· Dry eye.
· Corneas with insufficient thickness (too thin) for the defect to be corrected.
· Corneal pathologies, such as, for example, keratoconus, chemical burns, scars.
· Other ophthalmological pathologies, such as glaucoma, ocular diabetes.
· Pregnant and / or lactating women, since vision is unstable.
Postoperative
The postoperative period of FEMTOLASIK is safe and not very limiting. Visual recovery is fast (within a few hours the vision is very good) and the risk of incidence of complications is lower, with milder inflammation.
Photorefractive keratectomy (PRK)
What is it?
Photorefractive keratectomy (PRK) is a surgical procedure that uses lasers to treat refractive errors of the eye, such as myopia and hyperopia. It uses an Excimer laser in the same way as LASIK, and the results in correcting the vision of patients are similar.
The main difference between PRK and LASIK is that during a PRK procedure, the surgeon does not create a lid around the cornea, but instead removes or sets aside the upper part of the corneal layer (epithelium) before it the Excimer laser molds the cornea.
Advantages / disadvantages of PRK
Advantages:
· There are no risks of complications with the flap.
· Recommended for patients with thin corneas, previous glaucoma surgery, slight corneal scars, or other corneal problems.
Disadvantages:
· Mild to moderate pain postoperatively.
· Longer visual recovery period than LASIK / FEMTOLASIK.
· It may be necessary to use topical medication (eye drops) for a relatively long period (up to 3 months).
· Risk of corneal scars or opacities.
· Short-term (temporary) or long-term (permanent) risk of dry eye.
· Risk of problems with night vision, such as halos, glare, or bursts of light.
· Risk of insufficient or excessive correction.
· Risk of not achieving corrected vision prior to surgery.
Phakic intraocular lens implantation
What is it?
Those patients who have very high refractive defects (myopia, hyperopia, and/or astigmatism) that cannot be safely and effectively treated with LASIK or FEMTOLASIK.
The technique consists of surgically implanting a lens (inside the eye) to correct the refractive defect. The patient’s lens is not removed, so its ability to focus is preserved.
The intraocular lens can be placed either between the cornea and the iris (the colored portion of the eye) or just behind the iris, without removing the lens from the eye.
Indications
As the lens is not removed, it is especially indicated in young patients (18-45 years), especially those patients with high refractive errors.
Prognosis
Its prognosis, in terms of effectiveness, is similar to refractive laser surgery.
Intraocular surgery has proven to be very safe, but it is still more risky than laser surgery
The postoperative period is short and visual recovery is good, but the patient may have to use topical treatment (eye drops) for 2-3 weeks.
Refractive lens Exchange
What is it?
It is the extraction of the lens for purely refractive purposes (correcting refractive errors, such as myopia or hyperopia).
The surgical technique is similar to that used for cataracts, but with the difference that the patient does not have a cataract.
Indications
Although the refractive surgery of choice is LASIK / FEMTOLASIK, not all patients are candidates to correct their refractive errors using these techniques, mainly due to pre-existing conditions or the anatomy of the eye.
Patients over 50 years of age, in whom presbyopia is already evident and who may present the first signs of a cataract, would be the ideal candidates for this technique.
The use of multifocal intraocular lenses could be an added advantage, since it allows correction. Not only from distant refractive error but also from presbyopia.
Technique
The technique is similar to that used in cataract surgery (phacoemulsification).
Prognosis
The visual prognosis is very good. It is a very safe technique, but since it is intraocular surgery, it is not without complications.
One of its main advantages is the fact that this technique eliminates the need for future cataract surgery, in addition to presenting permanent results.
