NVD Flashcards
What component of the eye adjusts pupil size to allow light into the eye?
Iris
______ cells are less effective as light levels decrease.
Cone
Which type of vision is characterized by lack of color perception and requires off-center viewing?
Scotopic
How long does it take to recover dark adaptation due to exposure to a bright light?
5-45 min
When is the lens flexible?
When young
Where does the optic nerve enter the retina?
Optic Disc
What is the transition zone between photopic, and scotopic vision called?
Mesopic Vision
Dark adaptation normally takes how long?
30 - 45 min
How large is the night-blind spot?
5 - 10 deg
Why is the circular overlap in a scan pattern 10 degrees?
To ensure coverage of an area greater than the night-blind spot
What information does motion parallax provide aviators?
Aircraft speed and direction of movement
What is visual acuity?
The ability to resolve detail in an object
Crewmembers should overlap the previous field of view by how many degrees to ensure they compensate for the night-blind spot?
10 degrees
What is distance Estimation?
It tells how far away an object is from the viewer
What surface is the most difficult to hover over?
Water
What is the primary function of the iris?
Adjusts pupil size to allow light into the eye
What is the primary function of the lens?
Focuses light on retina
Rods and cones are contained in the __________?
Retina
What 5 components of the eye help us to see?
Cornea, Iris, Pupil, Lens, and Retina
What are the three types of vision?
Photopic, Mesopic, and Scotopic
This type of vision has best visual acuity and uses mainly cones.
Photopic
This type of vision has lowest visual acuity and uses mainly rods.
Scotopic
This type of vision has degraded visual acuity and uses rods and cones.
Mesopic
This is the chemical needed for better night vision and takes 30-45 min to build up.
Rhodopsin
It takes 5 -45 min to recover from ______________.
Flash Blindness
The day blind spot encompasses __________________.
5.5° to 7.5°of visual field
The night blind spot encompasses ________________.
5° to 10° center of visual field
__________ allows us to see where things are in relation to each other.
Depth perception
What are the different monocular cues?
Geometric Perspective, Retinal Image Size, Aerial Perspective, Motion Parallax
G.R.A.M.
Define geometric perspective
Objects have different shapes (geometry) when viewed at varying distances and altitudes
Define retinal image size
An image focused on the retina is perceived by the brain to be of a given size.
Image on the retina = size of object
Define aerial perspective
An object’s clarity and shadow help estimate distance
Clarity + shadow = distance
Define motion parallax
The apparent relative motion of stationary objects as viewed by a moving observer – Aircraft Speed and direction
Your estimate vector wrt to an object on the ground
What is spatial disorientation
The inability to determine position, attitude or motion relative to the gravitational vertical or the Earth’s surface
Confusing cloud formations with the horizon or ground
False Horizon
Missing or ignoring orientation cues to focus their attention on an object or goal
Fascination/Fixation
Landing with the searchlight too far under the nose causes the pilot to misjudge altitude
Crater Illusion
Falsely perceived self-motion in relation to another object’s motion
Vection
Pilot perceives a single light to be in motion when it is not
Autokenesis
Misinterpreting an unfamiliar object’s size to be the same as an object one is used to viewing
Size-Distance Illusions
