Mamisoa ANDRIANTAFIKA, MD FEBO
Eye Specialist
Brussels, Belgium

Short-sightedness or myopia

Left, original picture of Niagara Falls in background. Right, picture seen by a short-sighted patient.

Short-sighted vision of the Niagara Falls

Definition of short-sightedness or myopia

Myopia is a refraction anomaly causing images to focus in front of the retina.

This refraction anomaly can be caused by a longer eye and/or a higher convergence of most refractive elements of the eye, specially the cornea or the lens.

A short-sighted patient always has a clear near vision. He can see a clear image nearer than the emmetropic patient. The more myopic, the closer is clear vision.

For example, a cataract, which is an opacification of the lens usually due to aging can induce a myopia. Therefore, some older patients can feel a weaker far vision but starting to have a better near vision as age is increasing.

A short-sighted patient cannot see correctly at distance. He sees a blurred image from a certain distance. The more short-sighted, the shorter is the distance where vision is starting to be blurred.

That's why short-sighted patients get very close to read, because the range of clear vision is from a point near from the face to a short distance related to the degree of myopia.

Therefore, close images are clear and images at distance are blurry.

Correction of short-sightedness

To correct myopia, one needs to diverge pictures' rays to focus them on retina. We can use divergent glass or lens, the value of correction will the be negative (-).

Myopia can also be corrected by surgery in order to modify most refractive elements of the eye, i.e. the cornea, the lens or by adding a divergent lens inside the eye.

Usually, myopia between 0 and -6.5 dioptries is said to be low to moderate, and over to be high.

Some points about myopia

The short-sighted eye is usually longer, the retina then extends on a greater surface.

Retina tends to be thinner and have structural anomalies in all layers. It's also weaker.

In particular, holes or tears can appears in peripheral retina and lead to retinal detachment.

Therefore, myopia is a risk factor of retinal detachement.