The myopic eye
Myopia is a visual anomaly identified in Antiquity by Aristotle. It is the most common refractive error 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 Asian countries are myopic, compared to 30% in the 1970s. This phenomenon is found all over the world; in the USA, the myopic population has increased from 25 to 45%.
What is myopia?
Myopia is a refractive problem; the myopic subject sees poorly at a distance and very well up close. For them, it's as if they are looking through a magnifying glass. The image of a distant point is blurry for the myopic person; it forms in front of the retina and not on it, as is the case for an emmetropic (normal) eye. As a result, the myopic person sees a blur rather than a point!
On the other hand, when looking up close (without correction), the myopic person sees clearly without the need for the accommodation reflex.
In the vast majority of cases, myopia is "axial", meaning it is the result of an eyeball that is too long (+ 23.5 mm). It is less commonly due to an overly curved cornea.
Myopia is often diagnosed young, around 6 years old. Children read very close up, lean in to look at screens, squint to see far away... it often progresses until the age of 16 and stabilizes around 20-25 years old. It can progress again in women during pregnancies. Generally, the earlier it appears, the stronger it is. It varies depending on environmental and hereditary factors.
Most often, it affects both eyes and there is little difference between them.
It is often associated with astigmatism.
The word "myope" comes from the Greek muôps "one who squints to see better" and the Latin myop, opis "one who has poor eyesight".
Different degrees of myopia:
- From 0.25 to 3.00 diopters: mild myopia
- From 3.25 to 6.75 diopters: moderate myopia
- Beyond 7.00 diopters: severe myopia
- Myopia greater than 20 diopters is rare.
The visual acuity of a myopic person is less than 10/10° with a maximum clear vision distance of 5 m. A myopic person with -0.50 diopters has an acuity of 5/10° and their maximum distance of clear vision is 2 m from their eye. For a myopic person with -2.50 diopters, it is 1/10° and their clear vision distance will be 40 cm from their eye. This distance will be shorter the higher the myopia. A highly myopic person will have blurry vision beyond 10 cm; they cannot move around or perform daily activities (sports, work, cooking...) without correction.
From -0.50 diopters, driving is prohibited without correction; wearing glasses or contact lenses is mandatory, and don't forget to keep a spare pair of glasses in your car!
