LESSON 2.
NIGHT VISION IN AVIATION
TASK:
To incorporate night vision capabilities and limitations into
the aviation medicine program and the unit safety program.
OBJECTIVE:
You will be familiar with the structure, anatomy and
physiology of the eye; night viewing conditions and
techniques; and the hazards associated with night vision.
CONDITION:
You may use the lesson text and reference to complete the
review exercise.
STANDARD:
You must correctly answer at least 8 of 10 review exercise
questions.
REFERENCE:
FM 1-301 (Mar 83).
LESSON TEXT
1.
GENERAL
There are three types of vision, each type requiring a different
sensory stimulus or ambient lighting condition, Photopic vision is
experienced during daylight hours or when a high level of artificial
illumination exists. Mesopic vision is experienced at dawn, dusk and during
periods when the level of light is equivalent-to that of full moonlight.
Scotopic vision is experienced when low levels of light exist. In order to
understand the capabilities and limitations resulting from resopic and
scotopic vision it is necessary to understand the structure, anatomy and
physiology of the eye. Before flying in conditions of low illumination you
should also understand the hazards to night vision and what can be done to
prepare for flights made under those conditions.
2.
EYE STRUCTURE
The structure of the eye (Figure 1) can be compared to the structure of
a camera. The hard, white, outer coat of the eye (sclera) serves the same
purpose as the camera case. The cornea and the thin protective layer
covering the cornea (conjunctiva) compare to filters used to protect the
camera lens from outside elements. The iris and pupil can be compared to
the camera aperture and the eye lens is the same as the camera lens.
Finally, the retina can be compared to the film of the camera where the
image is projected before being sent to the brain for interpretation (film
developing). In order to get a clear picture, the eye (camera) must be in
focus. The eve accomplishes this by the use of muscles to extend and
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