Evening star., 1940-10-16
Navy Pilots Eyes
Checked for Special
Types Of Perfection
Unusual Conditions in
Flying Over Sea Call
For Exceptional Keenness
I, L. 81
(Tenth and last OF a SerteS.)
By THOMAS r. HENRY.

by lHOMAS n. HENRY.
The most rigid eye tests ever
known are being used by United
States Navy doctors for prospective
aviators.
The vision requirements of a sea
flyer must be far above what would
be considered normal for any other
human being. Navy Medicol Corps
officers explain, because of the un-
usual conditions with which h must
cope-some of which have been the
subjects of recent experiments.
One of the worst of these is
"glare." Bright sunlight turns the
surface of the sea, seen from above,
into millions of flashing lights.
Amidst these and the cloud reflec-
tions it is almost impossible to pick
out an object. The difficulty In
especially serious when a squadron
IS landing on the deck of an aircraft
carrier. A complex maneuver must
be executed to get the planes in po-
sltlon to come down, one after an
other with clocklike precision, on
the narrow space. A single bad
landing may break up the whole
operation. The entire maneuver is
executed according to flag signals
from the deck of the carrier. The
possibility of misleading these sig
mails in the face of the glare all
around them is great, and the least
deficiency in visual acuity is likely
to cause a mishap.
Depth Judgment Vital.
Another requirement of the Navy
aviator which is not shared by his
brother of the Army service is a
normal, or better than normal
stereoscopic sense, or ability to
Judge depth. The physiological
basis of this is obscure. but it can
be brought out by Navy tests. In
the ordinary affairs of life this
ability to judge up and down dis
tance with reasonable accuracy
seems natural One is aided by all
sorts of landmarks. The aviator
coming down on land estimates by
reference to towers, roofs, walls,
trees, etc. Under the sea flyer is
only an expanse of level sea, with no
altitude landmark anywhere. He
must rely entirely on the obscure
stereocopic sense which in many
persons is very deficient, although
they never realize it 1t is pri-
marily, the doctors believe, a nat
ural faculty which can be trained
to some extent.
Another factor which must be
tested is what Navy eye specialists
call the fusion center" of the brain.
It has nothing to do with the eyes.
per Sc, but is the general ability
to pick definite forms out of a con-
fusion, such as cloud banks or toss
Ing pillows. Everybody is doing
this a good deal of the time. The
brain hates a meaningless world.
But the Navy flyer must do it more
than anybody else. He must be
able to differentiate, for example,
the traces of a submerged subma-
rine in the open sea. Hour after
hour this fusion center is subject
TO constant strain.
firing Rate Varies.
Tests have shown that it gets tired
IN some persons much more quickly
than with others. This center is
not localized, as is the case with
the center of vision at the back of
the brain, and apparently is a gen.
eralized function in which several
parts of the cerebral cortex take
part. The candidate for naval avia-
ton without an exceptionally strong
fusion center is out of luck.
Another requirement, shared
largely with the Army pilot, is good
perlpheral vision, the ability to see
out of the sides of the eyes. Or
dinary normal vision requires only
that person see what lies straight
ahead. One can combine the things
seen by both eyes to make up the
general scene. The head can be
turned over wide angle BY twist
ing the neck sufficiently one can
see everything that lies behind
without moving any other part of
the body.
The Navy flyer hardly can twist
his neck at all because of the nee
essary flying suit in which he is
imprisoned. The best he can do is
to move his eyeballs. To see and
interpret objects even slightly to
one side he can no longer use both
eyes. Central vision depends on
different part of the retina of the
eye than side vision A man might
pass with flying colors all ordinary
occular tests and still be nearly
blind for side objects.
The peripheral vision is especially
important in such a maneuver as
landing on the deck of a carrier.
The flyer not only must see clearly
what lies straight ahead of him.
but he must see to the sides to
prevent collision with his comra des
In the same formation. The glare
problem is accentuated for flyers
OF planes with metal wings below
the cockpits There is also the
doubly reflected glare from the
clouds which becomes of special i'm
portance when flyer is caught
between two cloud layers.
Lake Landings Tricky.
The problem is made worse, the
Navy eye doctors say, by the fact
that the instrument board usually
is black and flyer must adapt his
eyes both to this background and
the glare outside.
Another problem peculiar to the
Navy aviator is that of landing on
interior bodies of water, such as
small lakes, which serve as perfect
mirrors of the surrounding country.
Looking downward it is difficult
to distinguish the water from the
hills and forest reflected in it.
Solution of these problems of
eyesight, on which the Navy's best
specialists are at work, cannot be
by any kind of glasses, the doctors
say Flying over the sea. these
are likely to be fouled at any time
and when this happens the only
thing to do is throw them away.