THE TRUTH ABOUT MYOPIA AND HEREDITY
One of the saddest realities of contemporary eye care is that although there are a few vision specialists with at least a moderate interest in the cause and prevention of myopia, most of their colleagues show not the slightest interest in this work. They continue to claim that no one has ever proven that acquired myopia is not inherited, and that there is therefore no reason to believe that this problem can be prevented. It is difficult to understand how this hereditary theory can still persist in spite of decades of research proving the close connection between excessive close work and myopia development.
"Heredity" does not cause myopia as many people believe. It does, however, play a role, and it is important to understand exactly what that role is.
Myopic parents do tend to raise myopic children, and it has therefore often been stated that heredity is the most important single factor in the cause of myopia. However, this tendency can be explained in another way. In those families where the parents are well educated and do considerable reading, the children will normally be well educated and do much reading also. The myopia of the children is not inherited but acquired, because they follow the example of their parents. Heredity can be a factor to the degree that reading ability or the desire to read is inherited, but it is the reading, not the hereditary factor, which is the cause of myopia. It is, however, necessary to explain why, of all the people who do close work, not all become nearsighted, and only a portion of these nearsighted people experience the more progressive form of myopia. Wide variations can and do exist even among children in the same family, growing up under similar conditions.
Ask yourself if there is a difference between these statements about acquired myopia:
At first glance, the two statements seem to say much the same thing, but they are actually quite different. The first one is false and the second one is true.
The latest research makes it quite clear that acquired myopia develops from excessive accommodation. Myopia is therefore most common in advanced, literate societies and is rare in primitive, illiterate societies.1 This is not to say that an illiterate person could not develop myopia. Even an illiterate person might be spending hours each day in some form of close work requiring excessive accommodation that could lead to the development of myopia.
That many people have gone astray in their thinking is obvious when one hears such statements as: "How can two children both do a similar amount of reading and yet one develops myopia and the other one doesn't? The cause must be heredity".
Actually, there are many possible factors, both known and unknown, which could account for such differences, and it would be very difficult to determine which factor is most important in any individual case. Some of these factors are:
The point to be made here is that none of these factors is the cause of acquired myopia. Generally speaking, these factors can only influence the rate of progression of the myopia if the environmental cause is present. If the cause is absent, virtually no one will develop myopia. The cause, of course, is an unnatural amount of accommodation.
Similar confusion about heredity exists when talking about other health problems. We know that some people never get tooth decay even though they eat an atrocious diet of refined foods, and there are many people who foolishly say that this proves that tooth decay is not due to faulty diet but is inherited. Yet, the simple fact is that tooth decay would virtually disappear if we all ate a proper diet of unrefined foods.2 Our hereditary differences would then be of no importance because the cause would be absent.
As another example, suppose that two people are heavy smokers. One of them dies from lung cancer at an early age and the other lives to be 100 and dies a natural death. It is obvious that there must be constitutional differences between the two, at least with regard to their ability to withstand air pollution. However, wouldn't it be foolish to attribute the early death to "heredity." If the cause (tobacco smoke or some other environmental poison) were not present, neither of the two would develop lung cancer.
Above were listed some of the factors that could affect the possible development of myopia in an individual, if the cause was present. We can list in a similar manner some of the factors that could partially determine whether or not an individual will develop lung cancer from smoking:
The above examples are simplified, of course, but they point out the need to stop talking about heredity as if it was a cause of these health problems. In the absence of an obvious congenital defect, it is incorrect to say that myopia is caused by an eye that is too long, or a cornea that is too steep, or a lens that is too thick. There are people who are born with long arms and people who are born with short arms, but the arms still function properly. If the bone is long, nature provides long arteries, veins, muscles, nerves, and skin. Why must we continue to believe that the eye is different and that it is a collection of parts of haphazard sizes? By what logic can we assume that it is nature's plan that so many of our children will find their vision failing during their early school years? Why the widespread reluctance to accept an unnatural visual environment as the cause? We don't have any difficulty understanding that an unnaturally loud environment can permanently damage our hearing. But that excessive close work can cause myopia seems to be difficult for most people to comprehend.
Numerous researchers have found a higher incidence of myopia in girls than in boys. Heredity need not be the reason for this. It can be explained by the fact that boys have traditionally spent more time in outdoor sports activities while girls have more frequently turned to sewing, knitting and other close-work activities.
Many birth defects have been shown to be caused by faulty nutrition of the mother, although this fact is, unfortunately, not as commonly known as it should be.2 It is therefore probable that much congenital myopia falls into this category, and that heredity plays a negligible role even in this form of myopia. Myopic eyes can logically be considered as eyes that are "solving" the problem of excessive close work. Unfortunately, this results in loss of distance vision. There are many children who are unable to solve their problem in this way. They may find reading so tedious that they give it up; they may get headaches; one eye may turn out or in, etc. Such people are good candidates to become school dropouts. In fact, it has been found that dropouts are almost never myopic. This means that either 1) they lack the ability to read and understand, or 2) they experience vision problems, such as the above, when trying to read. In either case, they do not read and they do not develop myopia.
It is possible that at some time in the distant future, the course of evolution will have altered human eyes so that they can do more close work without destroying distance vision. This might come about by a gradual increase in the ability of the ciliary muscle to relax itself when the distance vision starts to become blurred. This "negative accommodation" ability is already thought to be present in human eyes to a certain extent, and it could be developed and strengthened through evolution.
At one time it was most common for myopia to begin to appear in children between the ages of twelve to fifteen. This led some investigators to believe that the myopia resulted from the changes that occur with puberty, and that myopia was thus a delayed response to an inherited characteristic. However, since children are now developing myopia at a much younger age level (because they begin their schooling earlier), we know that there is no relation between puberty and the development of myopia.
If myopia is inherited, we would not have seen the tremendous increase in myopia that has occurred in recent decades. Genetically determined changes do not occur so rapidly.
At one time, most of the lenses produced by optical companies were plus lenses to correct hyperopia or presbyopia. Minus lenses to correct myopia made up only a small percentage of their production. Now this situation has reversed, and far more minus lenses than plus lenses are produced.
The age at which acquired myopia begins can vary over a wide range - from the preschool years up to the age of forty. This fact suggests strongly that this myopia is not inherited, since inherited characteristics tend to occur at a relatively fixed age for a given population and environment.
While on the topic of heredity, we should examine the question, "Are myopes more intelligent than nonmyopes?"
Myopia and intelligence. From time to time, reports are published showing that myopes score higher than nonmyopes on intelligence tests and concluding that myopes are thus more intelligent than the rest of the population. These researchers usually go on to say that this proves that myopia is inherited since intelligence is largely inherited. They have even gone so far as to claim that the gene that lengthens the eyeball also stimulates the brain. Such a statement is indicative of the length to which some people will go to justify their claim that myopia is inherited.
If those people who inherit a high intelligence also inherit myopia along with it, then it should be possible to select the most intelligent individuals from a group of primitive illiterates and find considerable myopia in these individuals. The fact is that in illiterate societies almost no one is myopic. Where then is this inherited myopia? It obviously does not exist.
These researchers seem to be totally ignorant of the numerous studies which have shown repeatedly that myopes score higher than nonmyopes on intelligence tests because of their better reading ability and not because they are gifted with higher intelligence. Several papers on this subject have been written by Francis A. Young, former Director of the Primate Research Center at Washington State University. The following passage from one of these papers3 summarizes these studies:
Education versus intelligence: If this consistent finding - that the proportion of myopic persons increases with years of schooling - is accepted and combined with the known relationship between intelligence level and years of schooling (which parallels that for the development of myopia), it might be concluded that the myopic person who predominates at the higher educational levels is also more intelligent than the nonmyopic. It should even be possible to estimate intelligence by determining the refractive characteristics of the eye. Most of the studies that have attempted to demonstrate a relationship between intelligence and refractive error have found none, except when intelligence was measured by written tests. There is a positive relationship between performance on such a test and refractive error: myopic persons tend to score higher than nonmyopic. However, when reading ability is statistically adjusted for, the correlation of refractive error and intelligence approximates zero. The myopic person is a substantially better reader than the nonmyopic.
It has thus been shown beyond doubt that myopia is not inherited along with intelligence, but parents are still manipulated into believing that concave glasses on their children are a status symbol to be proud of - a sign of intelligence. They are being fed with misinformation so that they will not be upset by their children's myopia. Their attention is being diverted from what should interest them - the prevention of myopia.
Reasearch by Francis Young. Some additional work done by Francis Young needs to be mentioned here since no book on myopia prevention would be complete without it. Dr. Young was the director of the Primate Research Center in Pullman, Washington for many years starting in 1957 and has had more than eighty-five scientific papers published, many of them on the cause of myopia. By pointing out the errors of some earlier researchers and by systematically seeking the facts, Young has put together an accumulation of knowledge about myopia that is of tremendous importance. His many years of research has produced irrefutable evidence that there is no truth to the old belief that heredity is the cause of myopia. However, he has yet to receive adequate recognition and praise from the scientific community for his years of effort. Furthermore, his work has been mostly unknown to the public.
The work that he and his colleagues have performed falls into several categories. Some of these are: the study of the development of myopia in monkeys; the incidence of myopia in the Eskimos of Barrow, Alaska; and vitreous pressure measurements.
By using a hood to restrict the vision of monkeys so that they could not see more than fifteen inches (38 cm) from the eye, it was found that most of them develop myopia after a few months' time, just as humans do.4 Monkeys living in the wild, on the other hand, do not develop myopia.5
It was also found that the juvenile monkeys did not begin to develop myopia as soon as the adult monkeys did under the test conditions. However, once the myopia began to develop, it progressed much faster in the juvenile monkeys than in the adults.
The experiments also showed that the greatest amount of myopia developed when the level of illumination was around four foot-candles. In other words, if the light level is less than this, there is not enough light for the eye to focus properly and the eye does not make the attempt to focus or exert full accommodative effort. Once the light level rises above four foot-candles, the eye will be able to focus and exert accommodative effort. As the light level is increased still further, the eye needs to accommodate less and less because the pupil becomes smaller and the periphery of the lens is not used.
The above studies indicate that in both monkeys and humans a ciliary spasm is of greater magnitude in the younger individuals than in the older ones.
In order to confirm even more strongly that prolonged accommodation was causing these myopic changes, a group of animals was placed under the hoods for four months until they were showing a good change into myopia. At this point, the animals were left under the hoods but a drop of one-percent aqueous atropine was placed in each animal's eyes every morning and evening. Atropine is a drug that paralyzes the ciliary muscle and makes accommodation impossible for as long as the drug treatment is continued. In using this drug on humans it has been found that it results in a reduction in the amount of myopia measured and a cessation in the progress of the myopia while the treatment is continued. This was found to be true with monkeys also. The amount of myopia was reduced by about 0.5 diopters, and no further myopia progression was observed.
All of the monkey studies clearly indicate that between seventy-five and eighty percent of the animals show myopic changes, and the remaining twenty to twenty-five percent do not. The first stage is the development of a spasm of accommodation. Once the spasm develops, it is followed within two to four months by an increase in axial length. Some animals do not seem to develop this spasm and consequently do not experience axial-length myopia.
Since those animals that do develop myopia experience fairly high degrees of myopia (up to 7 or 8 diopters) with corresponding axial-length increases of several millimeters, the effect of prolonged accommodation on the development of myopia is unmistakable.
Of 130 parents, only two showed any myopia. One had -0.25 D and one had -1.5 D. All the rest had refractive errors between 0 and +3 D. In other words they were somewhat farsighted, which can be considered normal.
Regarding the children of these nonmyopic parents, a totally different picture was found. Fully sixty percent of the school children examined showed measurable amounts of myopia. Of the fifty-three individuals who were between twenty-one and twenty-five years old, eighty-eight percent were myopic. There was a beginning of myopia at about age ten, with a steady increase in the proportion of the children showing myopia up to ages twenty-one to twenty-five years. This is shown in graph form in figure 1. It is obvious that these myopic children did not inherit the myopia from their parents.
Furthermore, since both the parents and the children were still using the basic Eskimo diet, at least for part of the day, these changes cannot be explained in terms of a dietary change.
When an outside radio-frequency source is directed at the eye, the signal is amplified or attenuated according to the degree of separation between the two discs. The transmitter is surgically placed (under anesthesia) in the vitreous chamber of monkeys. When the monkeys have recovered from this simple procedure, it is then possible to measure changes in vitreous pressure without such artificial attachments as wires or needles and without the requirement of anesthesia. It is merely necessary to restrain the monkey's head during the measurements so that the radio-frequency source can be brought close enough to the eye (about two or three centimeters).
Studies with these monkeys have shown that the vitreous pressure is least when they are focusing on a distant object and that the pressure increases steadily as the object approaches the eye. The maximum increase is about six millimeters of mercury above the normal twelve millimeters of mercury. These studies thus show that there is a direct relationship between fixation distance and vitreous pressure.
From these and his many other studies on both humans and monkeys, Young concluded, "It appears quite clearly that myopia results from a continuous level of accommodation, and if one prevents this continuous level of accommodation from occurring, very little myopia, if any, should occur."4
The experience of numerous other researchers has also pointed to the visual environment as the cause of myopia. For example, members of submarine crews have become myopic due to the confined visual space in submarines.8
Young is not the only person who has done valuable research in myopia. There are others, and they all deserve our gratitude. The problem is that their research is ignored by those who should be using this new knowledge to benefit the people.
Eye disease and diet. While this book focuses on myopia, many people suffer from eye diseases such as cataract, glaucoma, macular degeneration and diabetic retinopathy. While the doctors would have you believe that this is due to heredity and that drugs and surgery are the only answer, the true cause is faulty metabolism due to improper diet. If you want to avoid these and other systemic health problems, you must get your fat intake down from the usual 40% of calories to no more than 10%. This will also bring down your cholesterol level which should ideally be under 150. In this way you will avoid the atherosclerosis that paves the way for these diseases. Many books on this subject may be found in your local library. Don't fail to become knowledgeable in this area. Don't depend on your doctor.