The myopic eye
Myopia is a visual abnormality identified since antiquity by Aristotle. This is refractive disorder more common in the world . Some ophthalmologists even speak of a global epidemic: according to a study conducted by the University of Canberra (Australia) 90% of young students in developed countries in Asia are myopic against 30% in the 70s. This phenomenon is found all over the world, in the USA the population of myopes has increased from 25 to 45%.
What is myopia ?
Myopia is a problem of refraction, the myopic subject sees badly from afar and very well up close . Everything happens for him as if he were looking through a magnifying glass. The image of a distant point is blurred for the myope, it is formed in front of the retina and not on it as in the case of the emmetropic eye (normal eye). As a result, the myope sees a spot and not a point!
On the other hand, when looking closely (without correction), the myope sees clearly without involving the accommodation reflex.
In the vast majority of cases, myopia is " axil ”, that is to say that she is the consequence of an eyeball that is too long (+ 23.5mm). It is more rarely due to a cornea that is too curved.
Myopia is often diagnosed young around 6 years old. The children read very closely, approach to look at the screens, squint their eyes to see in the distance... it often evolves until the age of 16 and stabilizes around 20-25 years . It can again evolve in women during pregnancy. Generally, the earlier it appears, the stronger it is. It varies according to environmental and hereditary factors.
Most often it affects both eyes and is little different between them.
It is often associated with astigmatism .
The word “ myope ” comes from the Greek muôps “who blinks to see better” and from the Latin myop, opis “who has low eyesight”.
Different degrees of myopia:
- From 0.25 to 3.00 diopters : low myopia
- From 3.25 to 6.75 diopters : medium myopia
- Above 7.00 diopters : high myopia
- Myopia greater than 20 diopters is rare.
The visual acuity of the myope is less than 10/10° with a Maximum sharpness distance at 5m . A myope of -0.50 diopters has an acuity of 5/10° and its maximum distance of clear vision is located at 2 m from its eye. That of a myope of -2.50 is 1/10° and its net viewing distance will be 40 cm from its eye . This distance will be all the closer as the myopia will be important. The highly myopic will have blurred vision beyond 10 cm , he cannot move around and practice his daily activities (sport, work, cooking, etc.) without being corrected.
From -0.50 diopters, driving is prohibited without correction ; wearing eyeglasses or contact lenses is compulsory without forgetting to have a pair of emergency glasses in your car!