Myopia

Myopia is the most common refractive abnormality.

The child is able to clearly see objects that are close to him but cannot distinguish those that are far away. With myopia the image of a distant object we are trying to see, is not focused on the retina but in front of it, so we are not able to have a clear picture. This happens either because the system of the refractive media of the eye (especially the cornea and lens) has more power than required (refractive myopia), or because the anteroposterior diameter of the eyeball is bigger (axial myopia).

Sometimes these two reasons combined give a cumulative effect. Myopia greater than 6 diopters is usually axial.

Because the reason that causes myopia is the construction of the eye (eg large anteroposterior diameter of the globe), we can see that to a certain extent it is inherited, like we inherit height or skin color.

 
Myopia development

Myopia starts between the ages of 6 and 16 years old and its detection is usually in school where the child needs to see for distance, for example, to read on the board.

Myopia starting at preschool age is generally more severe than the one that starts in school, but tends to remain constant.

An indication that can easily be noticed by parents or teachers and presumes that a child has myopia, is the tightness of the eyelids in an attempt to focus in a distance.

(The tightness of the eyelids may be an indication that the child has myopia.)

Tightness of the eyelids makes distant objects sharper because it causes a temporary flattening of the cornea, and because of the phenomenon of
"pin hole" (i.e. the narrowing of palpebral fissure is achieved, increasing the depth of field, like in cameras with closing the lens aperture). For the same reason the nearsighted see better during the day: Not only because the brightness facilitates the vision, but also because the reflex contraction of the pupils (miosis) causes the same phenomenon.

But the tightness of the eyelids cannot be continued for long and it quickly leads to eye fatigue or headaches, making eyeglasses necessary.

Myopia continues growing as the child grows, due to the increase of the eye’s size. After the end of puberty, the development of the body
is completed and myopia usually stops rising. The increasing of myopia after this period may indicate some form of malignant or degenerative myopia and needs further investigation. However such incidents are rare.

The myopic eyeglasses

Myopia "is corrected" with lenses, which are thinner in the center and thicker at the periphery (biconcave). With these lenses the images of the objects displayed in front of the retina, move backwards in order to precisely focus on it.

The myopic glasses, as other refractive abnormalities, do not cure or define treatment.

The answer to a frequent parent’s question about whether or not the use of glasses affects the course of myopia is negative. Myopia will take its course whether the child is wearing the prescription glasses or not.

In preschool, if myopia is at a low grade, glasses may not be necessary, but if prescripted, they should not be used continuously.

Though in case the child "squints" (exoforia coexists or intermittent exotropia) the use of glasses is mandatory not only for the correction of myopia but also for the development of normal binocular vision.

Generally during the school age, the size of myopia will increase and the child will need stronger glasses. Sometimes the child may ask for correct glasses, when the need for cleaner vision grows.

 

Myopia it the neonatal period

In premature neonates, a particularly high myopia with large fluctuations may occur but it tends to decrease with time.

Retinopathy of prematurity (a condition that occurs in very premature babies, who have been granted with oxygen) can also cause permanent myopia that usually does not grow.