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.
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
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
All eyes treated with positive lenses became consistently
more positive (hyperopic).
Negative lenses produced more negative (myopic) refractions
(focal states) in all eyes.
In a test of plus/minus lenses on left/right eyes, the eye
with the plus lens moved in a positive direction. The eye
with a minus lens moved in a minus direction.
The control group did not change significantly in any