Cure Article_The Shortsightedness_Oct 2022

The Shortsightedness behind Myopia

The article was written by: Dr. Martin Stallmann, Ophthalmologist from Paarl.

It’s all about focus. To get a clear, sharp picture, your camera has to be in focus. The focus must be tuned to the specific distance at which you want to photograph an object. For objects of varying distances, the camera has to change focus every time.

Your eye works just like a camera. As the object you look at changes distance, so your eye has to change its focus. Things change in your eye to keep the image sharp at varying distances. Your eye changes focal distance by modifying the shape of the lens inside your eye – this is done by a small circular muscle inside your eye that contracts and relaxes. The closer an object is to the eye, the more the muscle must contract to keep the focus. If the object moves away from the eye, the muscle relaxes again.

A “normal” (not shortsighted, not farsighted) eye has a completely relaxed circular muscle when it looks far away, further than 6 meters distance. That is why a basic eye test is done at 6 meters distance from the eye. When objects move closer to the normal eye than 6 meters, the circular muscle has to put in an increasing amount of effort to change the lens to keep the focus.

In a shortsighted or myopic eye (the Greek medical term), the circular muscle is already completely relaxed with objects at distances closer than 6 meters to the eye. Depending on the degree of myopia (how much shortsighted) this might be at 4 meters distance, at 2 meters, or even closer to the eye with severe degrees of myopia. So in a myopic eye that sees an object crisp and sharp at two meters distance, the circular muscle inside is completely relaxed. The problem is, that the muscle cannot relax more than 100%. With the object moving further away than 2 meters from this myopic eye, the image becomes more and more out of focus and blurred. The myopic eye is otherwise healthy and normal, it is not a “weak” eye, it is just out of focus for distances further than 2 meters.

We are all born with a genetic blueprint that determines in part, I repeat: in part, whether we will end up as adults with “normal”, myopic or hypermetropic (farsighted) eyes. Newborn babies have small eyeballs which undergo great changes in the coming years. The eventual size of an adult eyeball, the steepness of the curvature in front (the cornea), and the “power” of the lens are all greatly influenced by your genetics. If your parents are both myopic, your chances of having a crisp image of your cellphone screen and a blurred vision of the girl crossing the street (if you don’t wear your glasses), are good (if you prefer the cellphone).

But the growth and development of the eyes in children is very dependent on the imput these two cameras receive from the environment. At age two, the child’s brain is sufficiently developed (remember, it is actually the brain that sees – the eyes are just satellite dishes receiving and focusing the images) to see normally and clearly like an adult. Throughout childhood and teenage years, the eyes continue to grow and at 19-20 years they are fully developed. The eyes grow and develop according to the input they receive. If they are constantly focused on objects close-, over many years the outcome of the eye will be one where the least effort is required for viewing close-by objects; thus myopia ensues – eyes with constantly relaxed circular muscles for nearby objects.

Humans are getting more and more shortsighted. Myopic genes are reinforced by visual behaviour in young children (fixating on hand-held devices) who as adults pass on their myopic genes. Over the past decades, this trend has increased dramatically. Surveys indicate that by 2030 50 % of humans will be myopic. Evolution has equipped us with “normal“eyes. Eyes that can spot the approaching danger miles away, but still, with some effort from our circular muscles, can focus on small items in our hands. Myopic eyes need constant help to see approaching danger clearly. Glasses, contact lenses, laser surgery – all these aids for myopic eyes are available, but they cost money.

Hand-held screens have become so cheap and ubiquitous, every child is in great danger of ending up with one of them in their hands. And then the “myopiasation” of the eyes sets in. The younger children are when they start staring at their small screens, the higher the chance of becoming myopic.

Keep children away from hand-held screens and you improve their chances of developing normal eyes. You improve their chances to develop a normal attention span. You improve their chances to become empathic adults. You improve their chances to be creative.

I could go on and on with the benefits of keeping cellphones, tablets, and hand-held gadgets away from your children.

Children should look at the birds outside, they should keep their eyes on the ball!

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