Laser technologies: how to obtain good vision without glasses or contact lenses
Today, good vision without visual aids can be possible thanks to the latest laser technologies.
We asked the ophthalmologist about the different possibilities of laser eye surgery, the costs and the risks of such procedures.
Dr Mattana, could you briefly classify the most common visual defects and tell us how they can be treated?
In a healthy eye, the light rays' travel is modified by the cornea and the lens, so they can converge on the retina.
- In the myopic eye, which is longer than a healthy one, the light rays converge in front of the retina
- In the shorter hypermetropic eye, the rays converge behind the retina
- The astigmatic eye has an anomalous corneal curvature
All these visual defects result in an unfocussed vision and the only way for the patient to be able to see correctly is to either wear glasses, or contact lenses. The therapeutic alternative to wearing glasses or contacts is corneal surgery, with the aid of excimer laser technology.
What might encourage a patient to undergo laser treatment?
Refractive excimer laser surgery may be suggested to patients who have an exaggerated refractive difference between the eyes (anisometropia) or who do not tolerate the necessary vision correction. It is also indicated for those who cannot tolerate contact lenses or who have to work in environments where visual aids are not permitted.
How is the laser used in eye surgery?
The laser beam manages to remove tissue with utmost precision. It's impossible to perform this type of surgery by hand. We’re talking about ¼ of a micron (1000th of a millimetre) every time the laser strikes the surface of the eye. There is currently no other method that could guarantee this result. This is how surgeons can eliminate, or at least reduce, the defects caused by myopia, hypermetropia and astigmatism.
Which are the different laser surgery techniques?
- Photorefractive keratectomy (PRK) takes out microscopic parts of tissue from the corneal surface (photoablation), after the previous removal of a thin layer of tissue (epithelium).
- In laser-assisted epithelial keratomileusis (LASEK), the epithelium is not removed, as with PRK, but is instead lifted and repositioned, after the laser intervention.
- In laser-assisted in situ keratomileusis (LASIK), a flap of the corneal surface is raised and a thin layer of underlying tissue is removed using an additional laser, called femtosecond. This type of laser employs lower energy, emits extremely short impulses and is capable of performing surgically in the deeper part of the cornea (stroma) without damaging any of the superior layers.
- The SMILE technique has been developed in recent years. With the aid of the femtosecond laser, a tiny, lens-shaped bit of tissue (lenticule) within the cornea is created. Then, with the same laser, a small arc-shaped slit is made in the surface of the cornea, after which the surgeon can extract the lenticule through this incision and discard it. SMILE allows the surgeon to correct extreme myopia, up to 10 dioptres, in patients who have very little corneal thickness.
How long do the operations last, how painful are they and what kind of anesthesia is used?
By using topic anaesthesia (eye drops), the surgery is painless. All the techniques mentioned above bear very similar results, but the femtosecond laser can guarantee an optimal result faster and with less irritation. We are talking about 30–40 seconds of laser treatment.
Could you tell us how to behave as a patient after the operation?
After the surgery, it is important to follow the therapy suggested by the doctor. Usually, a patient takes 7 to 10 days to have a satisfying level of vision and about a month to achieve an optimal one. Only one month after the operation can you do sports and go to the sauna or swimming pool, apply make-up to your eyes and dye your hair. Neglect in following post-operative therapy and the deadlines of specialist checks can influence the final refractive result and cause complications, rarely even serious ones. It is therefore essential to follow the prescriptions of the surgeon.