But what causes these changes? What causes glaucoma? Is it genetic? Is the decay built into our genes or is it due to outside factors? Can glaucoma be brought on by the wrong diet, by drugs, or by other environmental factors? Perhaps the answer lies, once more, in a combination of both genes and environment. Some people may be genetically programmed to be vulnerable to certain sorts of environment. This at least would explain why some diets seem to have an adverse effect on some individuals and not on others. Certainly some types of glaucoma recur in the same family (though of course members of one family will tend to react the same way to an environmental etiology).

Equipment has been designed to measure accurately the pressure in the eye and to test the field of vision. There are also tests to measure the flow of aqueous fluid from the eye when stress is put upon the eye-pressure system. But even if an early diagnosis is made, treatment is not necessarily effective, and the final outcome can be almost complete loss of the fields of vision except at the centre of sight. Affected individuals can still see clearly in the distance, and can read clearly, but they are unable to move about with any confidence, because they cannot see anything that is not directly in front of them. They have lost their peripheral vision, and in acute cases they may even have difficulty in following a line of print. Such a condition is called `tunnel vision‘, and is accounted a form of blindness, a fact little _understood or appreciated by the general public.

The onset of this kind of glaucoma is very slow and many patients do not know that they are affected. Sometimes the first noticeable indication is a loss of colour hue discrimination. It occurs most frequently in post-industrial ‘civilized’ communities, but this may simply be because in such communities the average life-span is longer, or because, in technological societies, people are more likely to damage their eyes by too much close-work. Even so, senile or elderly glaucoma has a relatively low incidence. About two per cent of the population over fifty will have eye-pressure above the normal, but only in perhaps 0.2 per cent (one in every five hundred) of the age group will specific treatment be sought or required.

Because it tends mostly to affect people over fifty there are possible connections with senile peripheral blood vessel degeneration, which affects other sensitive tissues in the body. There are, however, other causes and types of the glaucomous condition, of raised intra-ocular pressure. Some of these are too rare to be worth describing here, but others are not.

Infantile glaucoma occurs when the baby is born with an abnormal outflow of fluid from the eye. This often means that the angle of the eye has developed without adequate outflow channels. At birth the tissues of the eye are soft, and as the eye-pressure increases the eye becomes bigger. This can be a painful condition, and the baby may be distressed and unhappy. The cornea of the infant suffering glaucoma appears especially large and is sometimes cloudy. The eyes, also unnaturally big, will look red. There will be quiet periods, without pain, but diagnosis is essential. The condition can be treated either with drugs (eye-drops) or with surgery, opening up new channels for drainage of the fluid from the eye. If treatment is not provided, however, the eye may become very severely affected, and treatment at a later stage will be pointless.

There is also a condition of juvenile glaucoma, equally rare, but, like the infantile form, capable of leading to a loss of vision. It is generally considered a late development of the infantile condition.

Some doctors consider minor forms of glaucoma to be present in children who subsequently become myopic. Early high eye- fluid pressure, in this view, causes the eye to elongate and thus cause short-sightedness. Increased pressure owing to excessive close-work is often cited as the classic explanation of myopia, but in fact this has never been substantiated clinically.

The modern, effective treatment of cataract is to remove it from the lens capsule, or, if necessary, remove the whole lens itself. From about the age of fifty onwards the ligaments which hold the crystal lens in place become weaker. The lens can therefore be quite easily removed from the eye by rupturing the ligaments, especially if they have been ‘prepared’ by appropriate weakener-enzymes. Special forceps or a ‘freezing probe’ then lift the lens out of the eye. Usually the surgeon will supply counter-pressure to facilitate this operation. Another technique makes an opening in the eye and tears out the lens capsule. The hard nucleus of the lens may be ‘broken up’ whilst it is still in the eye, and the debris then washed out.

Once the nucleus has been removed the cortex, which is softer, naturally disintegrates so that it too may be washed out.

Once the inner lens has been removed the surgeon will decide whether to replace it with an artificial lens, or not to replace it at all.

Suppose, for example, that both parents had a recessive trait `A’. If they had nine children the chances are that only three of them would be marked by ‘A’. But if they had only two children, the chances of either of their offspring showing trait ‘A’ are small indeed, whether the trait is for weak legs or musical genius. But if both parents had dominants of a certain trait, this would almost certainly come out in the offspring. And this, as farmers have known at a practical level for centuries, is the essence of breeding. But whereas farmers have an unwritten licence to `improve their stock’ by processes of trial and error that involve disposing of runt animals, humans in their own breeding do not. When an unknown Swiss woman wrote to George Bernard Shaw suggesting they should have a child together because he had the greatest brain in the world and she ‘the most beautiful body‘, Shaw declined with admirable prudence: ‘What if the child inherits my body and your brains?’ Nonetheless, all societies indulge in some selective breeding. Incest is a near universal taboo, although different communities have different standards of what is the impermissible degree of incest. Great attention is paid in the scriptures as to who may marry whom, how the identity of race may be preserved, but also how new blood may be introduced through the maternal line. Only amongst the ancient Egyptians was incest actively encouraged, and then only as an exception to a general moral law. Certain individuals (pharaohs) were deified, and then it was hoped to produce a new line of gods by careful close breeding. The theory was perfectly correct: hereditary defects were given a new lease of life. The same happened in Europe, among the royal families, but for somewhat different reasons. Hence the famous Habsburg Jaw.

To return to the retina. Most nervous tissue that is highly specialized and not reproduceable (remove any part of the retina and it does not grow again) begins to lose its sensitivity after the age of thirty, or thereabouts. Naturally it can continue to function well, but not at the same level of perfection. By the age of seventy most retinae will have begun to atrophy to the point where the individual cannot help but be aware of diminished vision. Where there are hereditary defects, the decline in sensitivity can set in much earlier.

The retina and choroid should be completely formed at birth. If they are not, good vision may never be possible. Again the iris and pupil may similarly be incomplete at birth, a condition known as coloboma. Sometimes these conditions appear to be inherited, sometimes not. Very premature birth may in itself be sufficient explanation as to why the infant’s eyes are not perfectly formed, but there again prematurity may itself be an inherited tendency in the mother.

On the other hand, certain infectious syndromes are clearly not inherited. The body’s method of confining an infection to a particular area is to wall it off with inflammation cells, and then fibrous tissue cells. But in some instances this defence mechanism fails. Either the infection, or its toxic by-products, or even the very active inflammation cells and their products, end up in the small blood vessels of the retina and choroid and create areas of tissue reaction. Even when such an area is very small some loss of vision can result. Whilst such a reaction is very rare, it is relatively less rare among hard drug users who introduce infections into their blood stream when injecting themselves with heroin or other potent substances. Without knowing it they sometimes inject altogether harmful ‘filler’ substances, such as talcum powder, into their veins, and these can cause very acute retinal problems. This is as much a social as a medical problem. Teachers and parents have come to assume that rigid behavioural codes as to right and wrong are either unnecessary or may even warp the individual child, and so a necessary respect by the individual for his or her body has to be learned the hard way.

Blood vessels, however, are not the only route by which infections can reach the retina. They can come from the front of the eye, especially when the cornea has been infected. A severe corneal infection can spread backwards through the eye and eventually destroy the irreplaceable retinal cells. This is only likely to happen when the cornea has in some way been injured, and an infection allowed to enter the wound. In most cases the patient is likely to seek medical advice before his retina is affected.

The literature of the eye subject is full of speculations as to the origin of these appearances. Some have attributed them to the presence of eye floating specks—dead cells or the debris of cells—in the vitreous humor, the transparent substance that fills four-fifths of the eyeball behind the crystalline lens. Similar specks on the surface of the eye cornea have also been held responsible for them. It has even been surmised that they might be caused by the passage-of tears over the eye cornea.

They are so common in eye myopia that they have been supposed to be one of the symptoms of this condition, although they occur also with other errors of refraction as well as in eyes otherwise normal. They have been attributed to disturbances of the circulation, the digestion, and the kidneys, and because so many insane people have them, they have been thought to be an evidence of incipient insanity. The patent-medicine business has thrived upon them, and it would be difficult to estimate the amount of mental torture they have caused, as the following cases illustrate.

A clergyman who was much annoyed by the continual appearance of eye floating specks before his eyes was told by his eye specialist that they were a symptom of kidney disease, and that in many cases of kidney trouble disease of the retina might be an early symptom. So at regular intervals he went to the specialist to have his eyes examined, and when at length the doctor died he looked around immediately for someone else to make the periodical examination. His family physician directed him to me.

I was by no means as well known as his previous ophthalmological adviser, but it happened that I had taught the family physician how to use the ophthalmoscope after others had failed to do so. He thought, therefore, that I must know a lot about the use of the instrument, and what.the clergyman particularly wanted was someone capable of making a thorough examination of the interior of his eyes and detecting at once any signs of kidney disease that might make their appearance. So he came to me, and I made a very careful examination of his eyes. He went away happy because I could find nothing wrong but he came back periodically just for a check-up.

Once when I was out of town, however, he got a cinder in his eye and went to another oculist to get it out. When

I came back late at night I found him sitting on my doorstep, on the chance that I might return. His story was a pitiful one. The new doctor had examined his eyes with the ophthalmoscope and had suggested the possibility of glaucoma, describing the disease as a very treacherous one which might make him go blind suddenly and which would be agonizingly painful. He emphasized what the patient had previously been told about the danger of kidney disease, suggested that the liver and heart might also be involved, and advised him to have all of these organs carefully examined.

I made another examination of the clergyman’s eyes in general and their tension in particular_; I had him feel his eyeballs and compare them with my own, so that he might see for himself that they were not becoming hard as a stone; and finally I succeeded in reassuring him.

This was twenty-five years ago, but I shall never forget the terrible state of nervousness and terror into which the man had worked himself by the time he came to me. It was even worse than that of the clergyman, who was always ready to admit that his fears were unreasonable. I examined this man’s eyes very carefully and found them absolutely normal. The vision was perfect for both the near-point and the distance. The color perception, the fields, and the tension were normal, and under a strong magnifying glass I could find no opacities in the vitreous. In short, there were absolutely no symptoms of any disease.

I told the man there was nothing wrong with his eyes, and I also showed him an advertisement for a quack medicine in a newspaper, which gave a great deal of space to describing the dreadful things likely to follow the appearance of eye floating specks before the eyes unless one began betimes to take the medicine in question at one dollar a bottle. I pointed out that the advertisement, which was appearing in all the big newspapers of the city every day, and probably in other cities, must have cost a lot of money and must therefore be bringing in a lot of money. Evidently there must be a great many people suffering from this symptom, and if it were as serious as was generally believed, there would be a great many more blind and insane people in the community than there actually were.

My patient went away somewhat comforted, but at eleven o’clock—his first visit had been at nine—he was back again. He still saw the eye floating specks, and was still worried about them. I examined his eyes again as carefully as before, and again was able to assure him that there was nothing wrong with them. In the afternoon I was not in my office, but I was told that he was there at three o’clock and at five. At seven he came again, bringing with him his family physician, an old friend of mine. I said to the latter:

“Please make this man stay at home. I have to charge him for his visits, because he is taking up so much of my time, but it is a shame to take his money when there is nothing wrong with him.”

What my friend said to him I don’t know, but he did not come back again.

I did not know as much about muscae volitantes then as I know now, or I might have saved both of the men just described a great deal of uneasiness. I could tell them that their eyes were normal, but I did not know how to relieve them of the symptom, which is simply an illusion resulting from mental strain. The specks are associated •to a considerable extent with markedly imperfect eyesight, because persons whose eyesight is imperfect always strain to see; but persons whose eyesight is ordinarily normal may see them at times, because no eye has normal sight all the time. Most people can see muscae volitantes when they look at the sun or any uniformly bright surface, such as a sheet of white paper upon which the sun is shining. This is because most people strain when they look at surfaces of this kind.

The specks are never seen, in other words, except when the eyes and mind are under a strain, and they always disappear when the strain is relieved. If one can remember a small letter on a test card by central fixation, the specks will immediately disappear or cease to move, but if one tries to remember two or more letters equally well at one time, they will reappear and move.

Usually the strain that causes muscae volitantes is very easily relieved. A schoolteacher who had been annoyed by these appearances for years once came to me because the condition had recently grown much worse. In half an hour I was able to improve her sight, which had been slightly myopic, to normal, whereupon the specks disappeared. Next day they came back, but another visit to the office brought relief. After that the teacher was able to carry out the treatment at home, and had no more trouble.

A physician who suffered constantly from headaches and muscae volitantes was able to read only 20/70 when he looked at the test card, while the retinoscope showed mixed astigmatism and he saw the specks. When he looked at a blank wall, or a blank white card, the retinoscope still showed mixed astigmatism and he still saw the specks. But when he remembered a black spot as well as he could see it, when looking at these surfaces, there were no specks, and the retinoscope indicated no error of refraction. In a few days he obtained complete relief from the astigmatism, the muscae volitantes, and the headaches, as well as from chronic conjunctivitis (inflammation of the conjunctiva of the eye). His eyes, which had been partly closed, opened wide, and the sclera became white and clear. He became able to read in trains with no inconvenience, and—what impressed him more than anything else—he also became able to sit up all night with patients without having any trouble with his eyes the next day.