What are the symptoms of myopia?

In low myopia, the only symptom is indistinct distant vision. In high myopia, in addition to distance problems, there is also a problem for near work, simply because the object has to be held very close to the eye, which causes a strain on the convergence mechanism of the eye.

What is the present day approach to myopia control and prevention?

(I) Need for myopia control

There is a growing body of evidence to support the belief that most myopia develops as a result of prolonged exposure to near-point activities. Researchers in America such as Francis Young at Washington, Joseph Nolan in Illinois and Donald Harvis in California have done extensive studies.

Their studies show:

(a) Girls tend to develop a higher degree of myopia than boys, and to develop it earlier.

(b) The earlier a child develops myopia, the greater the final degree of myopia developed.

(c) The age at which myopia starts developing has been decreasing steadily over the years. At one time it was most common for myopia to first occur in the child in the 12-15 age group. However, now-a-days children develop it much earlier, even at as young as 5-6 years.

(d) Myopia is extremely rare, almost non-existent, in illiterate populations, but increasingly common in literate populations.

(e) The great increase in the incidence of myopia in the general population is supported by data provided by the optical companies which show a much higher percentage of minus lenses ground (for myopes) as compared to plus lenses.

Perhaps the earliest correlation drawn between myopia and close work was by H. Cohn in 1867 who in a survey found increasing myopia in the school population in Leipzig starting at an early age where early application to near work was encouraged.

Recently the hypothesis was proved under controlled study conditions. A small Eskimo village in Barrow, Alaska, was, before the U.S. government instituted mandatory schooling, almost completely illiterate with negligible myopia both in children and adults. Ten years later, 75% of the children showed the commencement of myopia while their illiterate parents were normal. Obviously heredity or diet had no role to play. It was simply excessive application to near work.

A series of experiments on monkeys doing excessive near work at an early age, showed a surprising rise in myopia which was maintained as long as undue stress on near work was maintained. This work done by. Professor Young in Washington gave confirmatory proof with reproducible results.

All this data was thus evaluated and from it, a series of conclusions derived, which are described below, on how to prevent myopia.

(II) Myopia prevention

A great deal of work has been done on myopia prevention. Recent studies show a definite trend towards greater numbers of children becoming myopic at an earlier age in life. These studies have clearly shown that the major causative factor is the increase in the amount of near work done by a greater number of children during the growing years.

Urban centres like Bombay show the highest increase in myopia.

To better understand the mechanics of myopia prevention let us re-analyse myopia.

An eye which is myopic has the light entering it coming to a focus before it reaches the retina. Thus the eye will be in focus for near objects but not distant ones. It is also easy to see from the illustration that the myopic eye is one which is too long. The present-day understanding is that the progress of myopia depends on the focusing muscle (the ciliary muscle) which acts on the lens of the eye. Over a period of time the muscle tends to develop a spasm to which the eyeball adapts by increasing its length and this permanently aggravates the myopia.

Since a lengthened eye will not shorten, it stands to reason that one should prevent the eye from lengthening.

Thus, stress on the eye must be reduced so that the patient does not become shortsighted.

The cardinal rules to follow are the following. They may sound simple but are extremely effective and are as applicable to children as to adults.

(A) Reading distance

The first principle is to read in such a manner as to prevent eye strain. In the act of reading, the eyes have to converge or turn in and accommodate. Since the convergence and accommodation are inseparably tied together, excessive convergence should not be permitted. Convergence depends on how close the book is held for reading. A safe guide to the minimum permissible reading distance is the length of the child's arm, from the knuckles to the elbow. If the child rests his chin on his hand and his elbow on his reading material, it is the closest distance permitted. Under no circumstances should a child be allowed to take his eyes closer. For adults 14-16 inches is the correct distance until the age of 40 years.

Thus, the closer one gets to the reading material, the greater is the effort required of the focusing ciliary muscle, leading ultimately to spasm.

(B) Intermittent reading breaks

It is common knowledge among students, that after an extensive bout of reading, the vision "swims" and takes a long time to change focus for distance. Occasionally, the spasm is too much for the eye and the muscle suddenly relaxes completely leading to blurred near vision—typically in the examination hall itself.

Why this spasm occurs and how it can be prevented are both simple to appreciate and put into practice.

Protracted near application, in which the eye remains at a fixed accommodative effort is the cause of the spasm. The preventive technique is to intermittently glance away from the reading material.

Thus, we can enunciate another rule. At the end of every paragraph read, the eye should look up, away from the reading material.

Thus, in the course of reading, the child or adult must be strongly encouraged to "look up" even for an instant. Looking up allows momentary relaxation of the focusing muscles and helps prevent spasm from setting in.

If long hours of reading are to be put in as for example just prior to an examination, it is best to use the well-tested 40:10 ratio.

In simple language, this means 40 minutes of close work to 10 minutes of relaxation in which the eyes are permitted to accommodate for distance. Using this ratio, even 14 hours of non-stop work will not affect the eyes in any way.

(C) Correct desk placement

The degree of relaxation during looking up while reading depends upon the distance to which the eyes are permitted to change focus. The ideal reading desk would be near a window where the child's may occasionally glance out, completely relaxing the eyes. As a contrast the worst possible place to sit during study is to face the wall in the corner of a room, with the mistaken intention of increasing the child's concentration. A tired eye leads to a tired brain.

For the busy executive, the placement of his desk in a manner by which he can occasionally look into the distance will leave his eyes much fresher and in a far more relaxed state. It is well known that if the eyes remain fresh, the brain is more relaxed and can both absorb new knowledge more easily as well as take better decisions.

(D) Illumination

The ideal illumination is daylight. Daylight, it should be remembered is a mixture of all colours of different wave-lengths. The much-vaunted "daylight" bulbs and tubes emit purely a narrow spectrum of blue light and are anything but "daylight" with which they should not be confused.

As far as possible, the desk should be in such a location as to permit as much daylight as possible, if necessary augmented by artificial light.

As a general rule, if illumination must be artificial, a milky bulb gives better diffuse light. Fluorescent tubes are acceptable, but they must be in pairs with a diffuser, preferably of glass. A flickering tubelight should be never used.

(E) Watching the television

An ideal: distance is five times the oblique diameter of the screen in inches. Thus if your television has a 20-inch screen, the correct distance should be 100 inches or 8 feet and 4 inches. As far as possible, the brilliance control should be set at the minimum at which the picture is clearly visible.

The television should be preferably slightly lower than the level of the eyes, though in houses with children, a little above is acceptable.

The room illumination should be kept on. Viewing a TV in a dark room is guaranteed to strain your eyes.

The eyes must be allowed to swing away from the screen at intervals of 5 or 10 minutes. Staring at the screen will result in weepy watery eyes with a headache.

(F) Hobbies

Since excessive emphasis is already being placed on near work, both for the child and adult, as far as possible, hobbies should not entail too much close work. At the end of a hard day's reading, to take up a hobby like embroidery or fine model crafting is obviously going to play havoc with the visual system.

Intermediate range hobbies are best—like carrom or painting with a palette knife or even games where undue exertion is not required of the eye.

Lighting must be adequate for the work in hand.

(G) Posture

Upright posture is ideal. Reading in bed is acceptable only for a short interval, and must not be encouraged. Tilting, the head, to one side or reading lying on the stomach must be forbidden.

(H) Sickness

It is common for parents and relatives to supply books and reading material to a child who has fever or is recovering after a serious bout of sickness. Illumination in such circumstances is usually poor and this practice is almost certain to raise the myopic power of a child.

The situation is extremely bad and must be completely avoided. The child should not have any reading or close work, though toys and games are acceptable.

This is a critical time for the child since the eyes, like the rest of the body are in a weakened condition and extremely prone to overstrain and spasm.

The often-noticed rise in myopic power after a sickness is due to the above cause. The sickness has no direct effect on the eye. Though the detrimental effect of reading and prolonged close work had been reported by Professor Duke Eller of London as early as 1939, it is a pity that the public has never been sufficiently apprised of this problem.

Night reading

Myopia occurs and increases because an eye is pushed beyond its limit. At the end of the day, with a tired eye in a tired body, to push them is sure to strain the eyes, leading to spasm and myopia.

Schools place far too much load on the delicate eyes of children. Come exam time, study till late in the night is more the rule than the exception. After the exam is over, an eye check will reveal a rise in power. This has been noticed over and over again. The problem lies in the fact that a tired eye has been stressed beyond its design specifications and pushed beyond its limit.

However, it has also been noticed in controlled studies that work done early in the morning, with a fresh eye, seems to have no deleterious effects and does not lead to a rise in power.

Hence, a simple rule has been formulated especially for children. No reading after eight o'clock at night, not even, as is often asked, comics. If study has to be done, let the child wake up early in the morning. It is safe for the eyes.

The above rule also applies to adults, especially those with myopia.

Over the last 50 years, the incidence of myopia has steadily increased in the U.S.A. where recent surveys showed 50% of graduate students and 60% of honour students are myopic.

Francis Young of Washington, after 15 years of experimental work, states conclusively, "It appears quite clear that myopia results from a continous level of accommodation, and if one prevents this from occurring, very little myopia, if any, should occur."

Dustin Flores

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