Myopia: what it is and how to treat it
Myopia is a very common eyesight defect. It is the most common refractive defect in the world. In Italy it affects 1 in 4 people. We are talking about myopia, a problem that prevents objects from being seen well at a distance
Its onset depends on a genetic predisposition, but lifestyle factors, such as spending many hours in closed, poorly lit places, keeping your eyes fixed on TV, computer, smartphone or tablet screens, would also influence its occurrence or worsening.
The Covid19 emergency has forced many people to stay at home and use electronic devices more than usual, both in smart working and distance learning, with negative consequences on their eyes.
What is myopia
Myopia is the most common of refractive defects, i.e. those disorders characterised by the inability of the eye to focus images sharply, causing blurred vision.
Myopia affects distance vision in particular.
It generally occurs at school age, increases during the developmental period and tends to stabilise at around 20-25 years of age, increasing only slightly after that age (unless there are particular pathologies that make it worsen rapidly).
Causes of myopia
Myopia has genetic causes. Myopic people have a longer than normal eye, which means that light rays from distant objects are not focused exactly on the retina (inner membrane of the eye), as they are in normal eyes, because they are focused in front of it.
This results in blurred distance vision.
Numerous studies in recent years have also shown a close correlation between myopia and lifestyle.
In particular, the occurrence of the disorder is more frequent, especially in children, in those who spend long periods of time indoors, with artificial lighting and performing activities that require them to observe objects placed close to the because of their eyes for several hours.
Thus, computer use may accentuate the worsening of juvenile myopia, as it is a proximal activity carried out indoors.
The symptoms
The main symptoms are
- blurred vision when looking at distant objects. The greater the visual defect, the shorter the distance at which one can see well;
- the need to squint in an attempt to focus on distant objects. The term myopia derives from the Greek word myo, which means “to close” and indicates the habit of short-sighted people of squinting their eyes in order to see better from a distance;
- eyestrain and headaches due to the constant effort of focusing.
Myopia correction techniques
There are various options for correcting myopia. The most suitable is assessed by the specialist depending on:
- age of the person;
- severity of the visual impairment.
In addition to corrective spectacles, which are the most common method, particularly in children and adolescents up to 14-16 years of age, and contact lenses, refractive surgery can be used to correct myopia. This involves the use of laser instruments, particularly the excimer laser and femtolaser.
Excimer laser with PRK technique
The excimer laser with PRK technique (PhotoRefractive-Keratectomy) is the most experienced treatment in the world (performed since 1990).
It consists of remodelling the front surface of the cornea, the first lens of the eye, after mechanically removing the surface epithelium (de-epithelialisation procedure).
A “natural contact lens” of the desired dioptric power is sculpted to correct the defect.
Only the precision of the laser beam allows patches of corneal tissue of one micron (one thousandth of a millimetre) to be removed at each “spot” (blow).
It is therefore a treatment that has the advantage of being superficial, without the surgeon having to manipulate the eye and therefore without intra-operative risks.
Femtolaser with Lasik technique
The Femtolaser with Lasik or Femto Lasik technique involves an initial stage in which the femtolaser cuts the cornea sagittally.
The corneal flap is then lifted by the surgeon who, with the second instrument, the excimer laser, modifies the curvature of the cornea by hollowing it out internally according to the required treatment parameters (as in PRK).
This technique makes it possible to correct not only myopia but also other refractive defects, hypermetropia and astigmatism.
Femtolaser with SMILE technique
The Smile technique (small incision lenticule extraction) is the latest available for correcting myopia and uses only the femtolaser, which cuts a lenticule (a kind of contact lens) inside the intact cornea equal to the value of the myopia/astigmatism to be corrected. The lenticule is extracted by the surgeon through a micro-cut.
It is a very sophisticated and minimally invasive technique, as it uses a cut on the cornea of only 2 millimetres and therefore:
- the corneal surface is respected as much as possible;
- the patient’s functional recovery is very quick, calculable in a few days;
- the tissue settles in real time.
It should be said that refractive surgery can only be performed when the myopia has been stable for at least a year and only after a careful assessment of the eye with specific examinations (measurement of the corneal thickness, corneal mapping, assessment of the pupil diameter, etc.) that allow the correct selection of candidates for surgery.
Refractive surgery: is it painful and what are the results?
Surface treatment (PRK) is painless for the patient, whose eye is anaesthetised.
The discomfort and pain starts 2 – 3 hours after the procedure and lasts for a couple of days.
The femtolaser treatment, on the other hand, is uncomfortable for 5-6 minutes, but does not bother the patient in the days following the treatment. Complete healing usually takes about 2 to 3 months.
It is useful to remember that the laser treatment is programmed on the value of the dioptric correction of the moment and therefore it is advisable that the defect is stable for 1 – 2 years.
Whichever technique is adopted to obtain the desired results, it is essential:
- the pre-operative phase;
- the exact assessment of the refractive defect, corneal curvature and thickness, pupil diameter, from which a highly customised computerised programme is derived for each eye.
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