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The Human Eye in Space

Oct 08, 1999 1025 Words
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 is the

degree to which the details and contours of

objects are perceived. 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 the eye.

# 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 (Perth,Australia.)"

The above observation was made by Gordon

Cooper in Faith 7 [1963] and which 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. Conclusion: 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. Solution: 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 Glasgow.

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 Anomaly.

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 through
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.

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