The Human Eye In Space
Human visual hardware is a result of a billion years of
evolution within the earths atmosphere where light is
scattered by molecules of air, moisture, particular matter
etc. However as we ascend into our atmosphere with decrease
density, light distribution is changed resulting in our
visual hardware receiving visual data in different format.
Some Aspects to Consider:
1. VISUAL ACUITY
The degree to which the details and contours of objects are
Visual acuity is usually defined in terms of minimum
separable.Large variety of factors influence this complex
phenomenon which includes :
# Optical factors- state of the image forming mechanisms of
# Retinal factors such as the state of the cones.
# Stimulus factors such as illumination, brightness of the
stimulus, contrast between the stimulus and background,
length of time exposed to the stimulus. * Minimum
separable: shortest distance by which two lines can be
separated and still be perceived as two lines.
"During the day, the earth has a predominantly bluish
cast.....I could detect individual houses and streets in
the low humidity and cloudless areas such as the Himalaya
mountain area....I saw a steam locomotive by seeing the
smoke first.....I also saw the wake of a boat on a large
river in the Burma-India area...and a bright orange light
from the British oil refinery to the south of the city
The above observation was made by Gordon Cooper in Faith 7
 and generated much skepticism in the light of the
thesis by Muckler and Narvan "Visual Surveillance and
Reconnaissance from Space Vehicles" in which they
determined that a visual angle of ten minutes was the
operational minimum, and that the minimum resolvable object
length [M.R.O.L] at an altitude of 113 miles would be 1730
ft. This limitation of acuity was revised the next year to
0.5 seconds of arc for an extended contrasting line and 15
seconds of arc for minimum separation of two points sharply
contrasting with the background.
Orbiting at 237 miles in the skylab, it was possible to see
the entire east coast [Canada to Florida Keys] and resolve
details of a 500 feet long bridge based on inference. Of
interest is the fact that even though the mechanical eye
[camera systems] can resolve objects greater than fifty
times better than the human eye, without the human ability
to infer, interpretation of the data is meaningless.
Visual acuity in space exceeds that of earth norm when
objects with linear extension such as roads, airfields,
wake of ships etc.
2. STEREOSCOPIC VISION
The perception of two images as one by means of fusing the
impressions on both retinas.
In space one has to deal with a poverty of reference
points. For hardware evolved in a reference oriented
paradigm, this possess a grave problem. Once out of the
space craft and gazing outward, the eye can only fix on the
stars [without even a twinkle] which for all practical
purpose is at infinity ie. without stereoscopic vision
"Empty field myopia" prevails.
Empty Field Myopia is a condition in which the eyes, having
nothing in the visual field upon which to focus, focus
automatically at about 9 feet .
An astronaut/cosmonaut experiencing empty field myopia
focusing at 9 ft would be unable see objects at a range
close as 100 ft. If another spacecraft, satellite,
meteorite or L.E.M entered his field of vision, he would
not be able to determine the size nor the distance.
Man does not face any hostile environment in his birthday
suit, the clothing industry and need for walk - in closet
say it all. In space we will wear our exoskeleton just as
we wear winter jackets in winter and we will wear our
helmets with visors to maintain our internal environment,
filter out all those nasty rads etc. Since Empty Field
Myopia is secondary to loss of reference points why not
just build them into the visor itself giving the eye points
of reference-- create a virtual reality ??? This line of
speculation leads to amazing concepts...... To learn more
about the concept of virtual universe in the helmet read:
Journal: Air & Space, [Smithsonian Publication] article:
Big Picture by Steven L.Thompson. illustrated by Dale
About creation of virtual universe with new computer and
software tech in the helmets of F-16 fighter pilots-- this
is not a theoretical possibility but a reality. A MUST READ.
Note: One aspect of adaptation to microgravity [space
sickness] is an increased dependence on visual as opposed
to vestibular mechanisms in the stabilization of retinal
image during head movements only underscores the importance
in being aware of our visual ability.
3. PERCEPTION OF COLORS.
Studies done by the Russian cosmonauts on effects on
perception of colors in space suggests a reduction in the
perception of brightness of all colors. The greatest
degradation seem to affect purple, azure, & green.
4. LIGHT FLASHES.
Not the so-called fireflies noted in orbital flights by
astronauts [shown graphically in the movie right stuff] but
lights as faint spots / flashes seen after dark adaptation
in the cabin of the Apollo missions. Generally described as
white/colorless and classified as three types.
# Described as "spots" / "starlike" 66 % of the time.
Appearing in both eyes simultaneously or one eye at a time.
# Described as "streaks" 25 % of the time.
# Described as "lightning discharge seen behind clouds" 9
% of the times.
It was of interest that the very same astronauts who
reported them in the Apollo flights failed to see them in
previous Gemini flights. After the Apollo flights this
phenomena was noted by the crew of all three Skylab
missions especially when they crossed the South Atlantic
W.Zachary Osborne, Ph.D., Lawrence Pinsky, Ph.D., at
University of Houston & J.Vernon Bailey at Lyndon B.
Johnson Space Center conducted an investigation on this
phenomena and concluded that they were due to heavy cosmic
radiation penetrating thru the craft and impinging on the
retina to cause this phenomena of flashes. The fact that
this was noted only after the eyes were darkadapted points
to retinal interaction than optic nerve per se.