Acquired Myopia

Myopia or near sightedness affects more than a quarter of the population in the Developed World. Alarmingly, over the last 50 years, the number of reported myop cases has steadily increased, bringing into question the traditionally held view that myopia is largely hereditary in nature. Research studies over the last few decades have proved that 'environmental factors' can significantly contribute to the acquisition and furtherance of myopia, and also that pinhole glasses can help combat this growth. But, perhaps more controversially, it is the discovery that our standard treatment for myopia - a pair of concave or 'minus' prescription glasses - whilst providing temporary clear vision, is actually accelerating myopic deterioration in the eye!

Near sightedness almost always develops during childhood. It is caused by the growth of a more spherical cornea, or an elongation of the eye through a build up of pressure in the vitreous chamber of the eye. Either way, light rays entering the eye come to focus at a point in front of the light sensitive retina. The light rays cross paths and begin to diverge before striking the retina, casting a blur circle on the retina itself. In the young, all elements that make up the eye are in a constant state of growth. These mechanisms are naturally more susceptible to 'external' influences that might cause an element of the eye to grow more slowly or more rapidly than would normally be the case.

Now, every child needs to learn to read and write. This often requires a child's eyes to focus on work close-up, such as when reading a textbook, writing or using a computer screen. For an unaided eye to focus in the short-distance, the ciliary eye muscle tenses in order to thicken the eye lens. The thicker lens focuses light rays into a single point on the retina at the back of the eyeball, so the eye can see clearly. Constant close-up focusing causes the eye muscle to spasm, the sclera membrane surrounding the eyeball to weaken, and a related increase in pressure in the vitreous chamber which stretches the sclera and elongates the eyeball further. It is easy to see then, how basic environmental factors, such as schooling, can create a worsening of a myopes condition.

Step in the traditional prescription eyeglasses. On the surface, they appear as the only real remedy to the situation, as a child cannot and must not forfeit their schooling. Unlike pinhole glasses that let only direct light rays through to the eye, concave or 'minus' lenses work by diffracting light rays entering the eye so they converge as a single point on the retina, enabling clear vision. The minus lens, by diffracting the light rays, actually makes the object being viewed appear closer than it really is. This begins a vicious circle in which the closer the object appears, the more stressed the eye lens becomes, and the greater the build up of pressure in the vitreous chamber. This is easily demonstrated when reading a book. When the wearer of the prescription eyeglasses reads a book, the words on the page appear closer than they really are. This means that the eyes must accommodate their focus more, leading to further stressing of the eye lens.

Pinhole glasses on the otherhand, do not make objects appear closer than they really are. By allowing only direct light rays to pass through the small aperture of the pinhole, pinhole glasses offer the wearer a greater depth of focus. Combined with the 'narrower than normal' beam of light entering the eye through the stopped down aperture, pinhole glasses reduce the blur circle on the retina, so enabling the eyes to see more clearly.

The Research

Over the past several decades research studies have been commissioned into acquired myopia, and how 'environmental factors' do accelerate eyeball elongation in myopes.

1) The eyes of monkeys, being similar to that of humans, were tested for the development of myopia. A hood was placed over a group of test monkeys to restrict their vision to a distance of 15 inches (38 cm). It was found that most of them developed high myopia just as humans do (Francis A. Young, "The Development of Myopia," Contacto 15, no. 2, June, 1971). Compared with the control cases of wild monkeys, who do not develop myopia in their natural habitat, this is clear evidence that environmental factors do affect the development of myopia. (Francis A. Young, "Visual Refractive Errors of Wild and Laboratory Monkeys," Eye, Ear, Nose and Throat Digest 27, August, 1965).

2) Eskimos living on the northern shores of Alaska were examined for myopia in the late 60s. It was found that the older generation of parents and grandparents, who lived a traditional outdoor life were not myopic. Three in five of their children, who had the benefit of compulsory education where there was a constant need to focus the eyes on close-up work, were found to be myopic (Francis A. Young et al, "The Transmission of Refractive Errors within Eskimo Families," American Journal of Optometry and Archives of the American Academy of Optometry 46, no. 9, September, 1969).

3) A report by the Navy's Bureau of Medicine and Surgery found that submarine personnel working in a confined visual environment develop myopia much faster than other Navy personnel who operate in less confined spaces.(Ira Schwartz and N. Elaine Sandberg, "The Effect of Time in Submarine Service on Vision," Medical Research Laboratory Report no. 253; Bureau of Medicine and Surgery, Navy Department project NM 003041.57.03).

4) In a study entitled "Accommodation, Refractive Error and Eye Growth in Chickens," and published in Vision Research., Vol 28, No. 5 pp 639-657, 1988, Pergamon Press, Frank Schaeffel, Adrian Glasser and Howard C. Howland found that: