Short-sightedness

The myopic eye is sometimes too long and sometimes has a cornea that is too curved. Together, eye length and corneal shape behaves like a system that is too convergent.

The eye projects distant images in front of the retina and you see them blurred. On the other hand, you see objects that are near vision without effort. Affecting about one-third of adults in Europe and North America, myopia is the most common visual defect, and its prevalence is increasing.

It usually appears at school age (in childhood or adolescence) and evolves into early adulthood, where it tends to stabilize. Some strong myopia, called myopia “diseases”, can evolve throughout life.

The nearsighted eye sees close-up, and blurred beyond a certain distance. This distance, beyond which the objects observed become “blurry”, makes it possible to quantify the degree of myopia, which is usually expressed in diopters (D).

The closer this distance is, the stronger the myopia. However, it is enough to be nearsighted of more than 1 diopter to see blur at more than 2 meters and not to have the right to drive.

The emmetropic eye has normal vision without optical correction. It is an eye whose anatomical qualities allow the image of a fixed object to form directly on the retina. Only 14% of the French are emmetropic.

An eye whose anatomical qualities are non-compliant is called ametropic. The image of an object does not form on the retina.

The different ametropia are myopia, hyperopia or astigmatism. Their importance is determined by the refractive power of the eye. That is, the nature and power of the optical correction that allows the image of an object to form on the retina of an ametropic eye.

The analysis of your vision, measured in tenths, and your optical correction measured in diopters, negative for myopic ametropia and positive for hypermetropic ametropia, is called refraction.

• Originally, we considered myopia to be genetic
• Today, we know that genetics is responsible for 3% of myopes. More than 100 genes are responsible for myopia but we do not know which ones are decisive
• Reading at too close a distance is a factor but the cause is not clear
• Environmental factors:
  • Exposure to daylight protects the vision. Being deprived of daylight leads to deformation of the eye and myopia
  • In Australia, which is a highly educated country, very few children are short-sighted because they spend a lot of time outdoors:
    • If 1 child has 2 nearsighted parents he will have 60% risk of becoming myopic if he spends a short time outside
    • If 1 child has 2 myopic parents he will have 20% risk of becoming myopic if he spends 2h / day outside

Humans see only three colours – Red, Blue and Green. Every other perceived colour is a combination of these. Blue light is the most present and intense wavelength outdoors. It protects against myopia because it stimulates the secretion of dopamine by the retina. Dopamine maintains the round shape of the eye. If the light is too weak or has too little blue light, then red light dominates, the retina secretes less dopamine and the eye lengthens. The combination of time spent outdoors, blue light and dopamine help the eye maintain its round shape.

• Atropine 0.01% would be effective but we lack perspective and these eye drops only exists in Singapore and Japan
• Taiwan has introduced a program since 2010: children have less post-school homework and do more than 2h / day of activities outside. As a result of this program there has been a myopic reduction of 10% per year
• Currently 90% of Taiwanese medical students are nearsighted

It is therefore necessary for children to play outdoors to reduce chances of them developing myopia.

A preoperative assessment is essential in refractive surgery. It allows your surgeon to choose the most appropriate surgical technique for you (which may be PRK, LASIK, SMILE,  or implants) and to check the absence of contraindications.

Indeed, even if refractive surgery corrects visual defects (myopia, hyperopia, and astigmatism), compliance with the contraindications avoids post-operative complications. The quality of the preoperative indication determines the quality of the result. This consultation also helps to answer your questions.

At Clinique de la Vision, for example, a preoperative consultation includes:

• measurement of ametropia (visual defect) to be corrected by refraction analysis
• the verification of the “dominant” eye (or “director”) essential when correcting symptoms of presbyopia
• the complete ophthalmic assessment with measurement of the intraocular pressure, examination of the fundus and especially the analysis of the transparency of the lens
• The analysis of corneal morphology (curvature, shape, thickness) thanks to corneal topography eliminates the contraindications to laser surgery and to choose the most appropriate surgical technique for the patient
• Aberrometric examination analysis of the optical quality of the eye
• Calculation of the implant is performed if lens surgery is considered
• Finally, other explorations can be done depending on the context.

It is only at the end of this assessment that a surgeon can make a recommendation. They can then choose the most suitable refractive surgery technique for you.

Finally, the surgeon must clearly explain the advantages, the possible undesirable effects and the expected results of their recommended procedure.

Surgeons can correct myopia with several laser techniques including:

• PRK: In PRK, the surgeon performs excimer laser photoablation on the surface of the cornea after removal of the epithelium
• LASIK: In LASIK, the surgeon performs excimer laser photoablation in the thickness of the stroma under a femtosecond laser-cut corneal flap
• SMILE: In SMILE, the surgeon performs the correction of myopia by ablation, through a mini-incision, a femtosecond laser cut refractive lens
• ICL: In the case of strong myopia, surgeons can implant a contact lens in the eye.