Page 313 - My FlipBook

MANAGEMENT OF LIGHT AND CARE OF THE EYES. 177
be confined to operating glasses or other work of similar small-
ness of area in which the outlying areas of distortion will not be
annoying. Even this annoyance will disappear after long prac-
tice. In this I speak from a clinical experience of forty years'
use of prisms in operating. In my seventies my vision is as
good as in my thirties.
The use of prisms is not equally valuable to different per-
sons. There is much difference in the pose of the eye muscles
of persons who are capable of perfectly normal vision. This is
best illustrated by comparison with a muscular pose that soon
destroys normal binocular vision. When the pose of the muscles
of the eyes is abnormal to a degree that renders it impossible
for the person to continue the adjustment for binocular vision,
squint occurs. This is called strabismus. This may be conver-
gent or divergent, i. e., the eyes may be crossed or they may
spread apart. The same thing to a lesser degree occurs in per-
sons permanently capable of normal binocular vision ; the pose
of the muscles controlling the positions of the eyes may be a little
abnormal one way or the other, but by a greater than normal
effort they succeed in doing the work. The person with a slight
tendency to divergent strabismus in the pose of the eyeballs at
ease has much more effort to cross them for near vision than he
who has the opposite pose tending to cross the eyes. It is the
person who has the tendency to divergence of the eyes who
derives the most important benefit from the use of the additional
aid of wisely adjusted prisms.
It will now be apparent that all of this adjustment must be
brought about by aid of the experienced oculist who has the
necessary apparatus and is skilled in making the measurements
upon which the adjustments of these aids to vision are based.
There is no other profession or calling in which men do so much
fine vision work with binocular vision as in operative dentistry.
The watchmaker and the engraver give up binocular vision and
use a single magnifying lens. The dentist does not. Therefore,
the dentist, of all others, should have the greatest care as to his
eyes and make the wisest use of the aids to accuracy of binocular
vision. One of his special cares should be comfort of binocular
vision and the continued usefulness of his eyes. The skilled
oculist should be his helpmate.