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43 Cards in this Set

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Discuss the Anatomy & Physiology of each of the following components of the eye:
a. Cornea: Clear, Convex, Anterior portion of the eye with the highest refractive index.

b. Lens: Located behind the cornea, the lens is biconvex and the primary refractive portion of the eye. Contracts: thicker Near, Relaxes: thinnerDistance

c. Retina: Innermost layer of tissue in the eye. Contains millions of photoreceptors (rods and cones) over the entire retina.

d. Optic Disk: The anatomical blind spot. The disks are located in different spots on each eye, so that when each eye is in use the blind spots will be negligible.

e. Cone Cells: Provide vision of details and color in bright light conditions. They are concentrated in the retina and become sparser in the periphery. Three types of cone cells exist, one sensitive to blue color, one to red, and one to green. The interpretation of the color happens in the brain, not the retina.

f. Rod Cells: Located mostly on the periphery of the retina. Allows vision in gray tones in dim lighting and provide peripheral vision. The primary cell in night vision.
Discuss the photochemical process of vision:
• Light enters the eye through the pupil and is received by cone and rod cells. The rod cells contain rhodopsin while the cone cells have photopsin I, II, III, and melanopsin. Rhodopsin aids monochromic night vision and green-blue lights. The photopsin I absorbs yellowish-green, II absorbs green, and III absorbs blue-ish violet colors. Melanopsin absorbs blue light. When light hits these photochemicals, they undergo a process called phototransduction which changes the light into electrical signals which pass along the optic nerve and are processed by the brain.
Discuss the process of dark adaptation:
• This adaption increases the eye’s sensitivity to light in dark environments. It is a chemical process and can take anywhere from 20 to 30 minutes to complete. The pupil will dilate and rod cell activity in the retina increases. Vitamin A aids in the reformation of rhodopsin so that dark adaption can take effect, and deficiencies in this vitamin lead to night blindness. Red lights only partially revert the eyes back to normal sensitivity whereas blue and violet light will revert it back to normal completely. Ultimately the rhodopsin concentration in your eye is increased.
Discuss retinal bleaching:
• In the dark retinal is in the cis form, but when it absorbs a photon of light it quickly switches to the trans form. This changes its shape and therefore the shape of the opsin protein as well. This process is called bleaching. The reverse reaction (trans to cis retinal) requires an enzyme reaction and is very slow, taking a few minutes.
Discuss the focal mode of visual processing:
• Focal vision is concentrated onto the fovea and accounts for 3 degrees of the visual field. It is used for recognizing and identifying objects. It is conscious and requires attention by the observer. It provides maximum visual acuity and depth perception. Also requires high illumination levels.
Discuss the ambient mode of visual processing:
• Used to orientate the observer to their environment, detect motion and positional environment. This vision doesn’t require attention and uses mainly rod cells. Poor visual acuity and color vision are results of this though. At night, this is the main vision used.
Discuss depth perception:
A. Binocular cues: There are 3 binocular cues: stereopsis, vergence, and accommodation or focusing of the image by changing the curvature of the lens. Stereopsis is working only to 200m. Vergence and accommodation are useful only to 6m.

B. Monocular cues: There are 8 monocular cues: size constancy, shape constancy, motion parallax, interposition, gradient of texture, linear perspective, illumination perspective, and aerial perspective. Size constancy, shape constancy, and parallax of motion are the most important cues for depth perception because they are available during flight and function well beyond distances available in binocular cues.
What is the difference between depth perception and distance estimation?
• Distance estimation is determining the distance in any direction from objects from the perspective of the viewer’s eye. It encompasses near and far and different angles. It can pertain to objects from the eye, or the distance between two objects, and distance in the right or left direction in relation to estimation. It is a learned process based on the concept of measurements and visual cues. Depth perception on the other hand is directly in front of the eye (focal vision.) An example would be looking into a tube and determining the distance of the object from the eye, and determining what is closer to the viewer in relation to other objects. This requires binocular stereoscopic vision, and when that is unavailable, visual cues must be present. Distance estimation is typically 2D while depth perception is 3D.
Describe the A&P and functionality of the Semicircular canals:
• The inner ears contain semicircular canals which are donut shaped and affixed 90 degrees of each other in approximately the pitch (vertical), roll (lateral), and yaw (horizontal) axes. They contain endolymph fluid with sensory hairs called cupola in an enlarged chamber. They sense angular acceleration if the threshold reached is .14o per sec2 to .5o per sec 2 of actual movement.
Describe the A&P and functionality of the Otolith organs:
• These are located in the inner ear at the base of the semicircular canals. It contains a bed of hair which is covered in a gelatinous material with calcium carbonate crystals suspended in it. As the head tilts, the crystals move across the hair in the gel material which sends a signal to the brain alerting motion is occurring. Linear acceleration can create an illusion in pitch up or pitch down.
Describe the A&P and functionality of the proprioceptive system:
• This senses where the body parts are in location to itself and whether or not it is moving, using a perception internal to the body. This deals mainly with musculo-skeletal mechanisms, tendons, and articular sensitivity. There are receptors in the muscles that sense pressure, light, temperature, sound and other experiences.
What is the cognitive level of processing associated with each of the sensory systems:
• Focal vision requires a high level of cognitive processing as you are putting forth attention on it. Ambient vision is more subconscious and can help direct your focal vision towards an ambient cue if it happens to catch your attention. Somatosensory systems require low levels of consciousness though and can be completely subconscious unless focused on. Hearing is mainly at subconscious levels, whereas “listening” is more cognitive.
Define sensory Illusion:
• A false perception of motion or position relative to the Earth. They can occur from visual misperceptions or vestibular errors
Shape constancy
: People have pre-determined ideas of what shapes objects are. When the actual object differs from this preconceived notion of what it should be, then a pilot may adapt the flight path to make it fit into what the notion would be. This can occur if a runway is angled. The pilot might change their angle of descent to compensate for the visual difference.
Size constancy
Another preconceived notion of what size an object should be. If something looks smaller than it should, it will be determined to be further away than it actually is. If something looks larger than normal, it may be seen as being closer than it really is.
Runway shape/size illusions
This can occur if a runway is on a slope. A runway angled down may make the aircraft seem like it is coming in too low. If the runway is angled up, it may appear that the pilot is coming in too high. Another common illusion with unknown runways is if a runway looks too small, it can be perceived that the aircraft is too high. Conversely, if it is too large the pilot may think the aircraft is too low. This can be countered with good briefs.
Terrain perspective
A good example of terrain perspective is the preconceived idea of visual cues such as trees. One runway may have trees that are 50 ft tall, and the pilot has become accustomed to that. If the pilot is landing at a different runway and the trees are 25 ft tall, the pilot may perceive a higher altitude than reality.
Aerial perspective
Lights in the sky which are bright often appear close, whereas lights that are dim may seem to be further away. Fog or other conditions which impair vision may also cause distances to be skewed.
Absent focal cues
This occurs during flight over featureless terrain. Such environments include sand, smooth water, and snow. This removes all focal cues and takes away the pilots ability to judge altitude, making them rely on instruments
The black hole illusion
Occurring mostly at night, the black hole effect happens when there is a lack of a horizon and on approach to an airfield without surrounding lights. The pilot flies towards the lights, but a lack of ambient cues prevent accurate aircraft pitch to the real horizon. The pilot uses only visual cues while landing and follows a parabolic path instead of normal descent. The outcome is the aircraft landing short of the runway.
Whiteout and Brownout
Rotary and Harrier aircrafts can experience whiteout and brownout conditions. This is when they are close enough to ground level while landing or on low hovers, and sand or snow can form a thick cloud and block all fields of vision.
Autokinesis
Happens when a single light is stared at for a few moments against a dark background. It could be a star, light from another aircraft, or ground lights. The light then seems to move around randomly. Larger and brighter lights seem to have this effect less.
Liner vection
Caused by observing movement in another object when you are stationary. This happens most of the time in peripheral vision, and the best example would be seeing a car roll backwards, and feel as though are you moving forwards because of that.
Angular vection
Also caused by observing movement in another object, and usually within the peripheral vision. This observation makes you feel as though you are moving yourself. An example of angular vection would be walking on a path through a rotating barrel, making the sense of falling over or rolling take place.
False horizons
When a horizon is created by a line of lights, which could be a highway, street lights, or even fishing vessels in a linear formation. Other false horizons could be sloping cloud decks, ridgelines, or coast lines.
Somatogyral illusions (general):
): Feels as if you are spinning. Can happen when semicircular canals have an inertial delay in the fluid. Extended constant rate turns begin to feel as being stationary, and deceleration of the turn will feel like turning in the opposite direction.
The leans
The most common semicircular canal misperception. Initial entrance into a banked turn stimulates a normal response in the semicircular canal. After a prolonged maneuver, the inertial difference is no longer a factor on the endolymph fluid, so the aircraft seems to level out to the individual. After the banking maneuver is over, the pilot feels as if the aircraft is now turning in the opposite direction. You may find yourself leaning towards the perceived banked direction.
Graveyard spin
This is a more severe case of the leans. In IMC conditions with no horizon, disorientation takes effect quickly. After a spin has occurred for a prolonged time without acceleration, endolymph fluid reaches equilibrium, and the pilot feels as though he has exited the spin when in fact he is still in it. Checking the instruments can help to alert the pilot of this illusion. Once out of the spin, the endolymph fluid in the yaw plane moves again and in the opposite direction. The pilot overcorrects and places the aircraft back into its original spin.
Graveyard spiral
Another more severe case of the leans. When in a banked turn long enough for the semicircular canals to reach equilibrium, the pilot goes to put the aircraft in straight and level flight, but then feels as though the aircraft is banked in the opposite direction. To compensate, the pilots unknowingly returns the aircraft to the original bank. Altitude seems to be lost, so the pilot pulls back on the stick and adds power, but this increases the bank and altitude lost, putting them into a spiral.
Oculogyral illusion
: Looks as if you are spinning, and can accompany somatogyral illusions. The vestibulo-occular reflex causes the eyes to track as if you were spinning while experiencing the same effects as the somatogyral illusion. This is exaggerated nystagmus.
Coriolis cross-coupling illusion
This causes a sensation of tumbling or spinning and is the result of a stimulation of multiple semi-circular canals at once. One canal is experiencing angular deceleration while another is experiencing angular acceleration. This can be from moving your head while in a turn or spin. The feeling can cause sensation in a plane not involved in either of the other two planes of movement.
Somatogravic illusion:
Somatogravic illusions involve the otolith organ and Gx. Positive Gx gives a pitch up sensation as negative Gx gives a pitch down sensation. The acceleration or deceleration moves the crystals on the otolith organ which simulates the head tilting up or down which then provides the false illusion.
Inversion illusion
This occurs during the level off of a high performance climb, most likely during IMC conditions. The pilot noses down to level the flight after the climb which causes the pilot to experience negative Gz and lineal acceleration which gives them positive Gx. This makes the pilot feel as though they are rolling backwards. The natural response to this is to nose down, yet that only puts the aircraft into a dive. If unrecovered by checking instruments, ground impact can occur.
G-excess illusion:
This happens when someone looks into a turn. The centripetal acceleration causes the otolith organ to create a pitch up sensation. This in turn decreases the feeling of the bank and the pilot will overcompensate and actually lose lift and altitude.
Oculogravic illusion:
The elevator illusion occurs with upward or downward acceleration. This stimulates the otolith organ, and since there is a vestibulo-ocular connection, your eyes will move with the sensory information, but lag momentarily. With downward acceleration, your eyes will look up and reflexively pull the nose upward to compensate, and vice versa with upward acceleration.
Define spatial disorientation:
Spatial disorientation is when you are unable to orientate yourself to the horizon of the Earth.
What causes spatial disorientation?
Spatial disorientation occurs when visual cues are absent or confusing
Discuss type I disorientation (Unrecognized):
The most dangerous. This happens when you believe the aircraft is in the desired attitude, but in reality is in an altered state. It happens due to relying on vestibular and somatosensory systems instead of using flight instruments when vision is impaired. Can lead to controlled flight into terrain if flying at low altitudes with high speed.
Discuss type II disorientation (Recognized
The least dangerous. Spatial disorientation occurs but you cross check your instruments and realizes what is happening. Recovery is completed by use of instruments.
Discuss type III disorientation (Incapacitating
The least common. Extreme disorientation and incapable of recovering even if the disorientation becomes recognized. If the disorientation is recognized, recovery may be impossible due to sensory stimulation being too great. Possible actions include ejection, other crewmembers helping with recovery, or autopilot.
What is focal dominance?
Vision accounts for the majority of input that we use to orientate ourselves in our environment. Focal vision can be used to override ambient cues, vestibular inputs, and proprioceptive senses.
Discuss prevention of spatial disorientation
the main chains of reactions to prevent spatial disorientation are procedural changes, improved instruments, instrument proficiency, autopilot, flight training, physiological training, instruction and experience.
Discuss recovery from spatial disorientation:
Recognizing spatial disorientation is the first key to recovery. Cross checking with instruments is essential. The use of autopilot or allowing the second pilot to take controls may help to recover from spatial disorientation. Some fighter planes may have a panic switch which will recover the plane to a wings-level attitude.