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THE VISUAL SYSTEM IN FLIGHT TERMINAL LEARNING OBJECTIVE Action: Manage the effects of visual limitations during flight Conditions: While performing as an aircrew member Standards : IAW FM 3-04.301, FM 8-50, AR 40-501, and AR 40-8 ANATOMY OF THE HUMAN EYE

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THE VISUAL SYSTEM IN FLIGHT

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THE VISUAL SYSTEM IN FLIGHT


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TERMINAL LEARNING OBJECTIVE

  • Action: Manage the effects of visual limitations during flight

  • Conditions: While performing as an aircrew member

  • Standards : IAW FM 3-04.301, FM 8-50, AR 40-501, and AR 40-8


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ANATOMY OF THE HUMAN EYE

  • CORNEA: The clear outer portion of the eye through which light passes.

  • IRIS: The colored portion of the eye which controls the diameter of the pupil.

  • Pupil: The dark center of the eye which allows light to pass through to the lens.


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ANATOMY OF THE HUMAN EYE

CORNEA


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ANATOMY OF THE HUMAN EYE

IRIS


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ANATOMY OF THE HUMAN EYE

PUPIL


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ANATOMY OF THE HUMAN EYE

  • LENS: Located behind the pupil it focuses light on the retina.

  • RETINA: Composed of many tiny photosensitive cells called rods and cones.

  • FOVEA CENTRALIS: Contains a very high concentration of cone cells but no rod cells.


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ANATOMY OF THE HUMAN EYE

LENS


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ANATOMY OF THE HUMAN EYE

RETINA


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ANATOMY OF THE HUMAN EYE

FOVEA

CENTRALIS


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ANATOMY OF THE HUMAN EYE

RODS & CONES

  • Named because of their shape

  • Rods are used for night and low-intensity light vision (Scotopic Vision)

  • Cones are used for day or high-intensity light vision (Photopic Vision)

  • Both used at Dusk or Dawn (Mesopic Vision)


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ANATOMY OF THE HUMAN EYE

RODS

  • Contains rhodopsin also known as vision purple

  • Rhodopsin bleached out by light making rod cells inactive

  • Extremely light sensitive (Scotopic Vision)

  • 30 to 45 minutes required to build up Rhodopsin (Dark Adapt)


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ANATOMY OF THE HUMAN EYE

CONES

  • Contains iodopsin

  • Identifies colors

  • Sharp visual acuity and color sense (Photopic Vision)

  • 7 million in fovea and parafovea regions

  • 1:1 ratio of cone cells to neuron cells


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ANATOMY OF THE HUMAN EYE

  • OPTIC DISK: The day blind spot. No rods or cones are present as the optic nerve enters the eye at this point.

  • PARAFOVEAL REGIONS: Mixture of rods and cones

  • PERIPHERAL REGIONS: Mostly composed of rods for night vision


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ANATOMY OF THE HUMAN EYE

OPTIC DISK


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ANATOMY OF THE HUMAN EYE

PARAFOVEAL REGIONS


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ANATOMY OF THE HUMAN EYE

PERIPHERAL REGIONS


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VISUAL DEFICIENCIES

  • ASTIGMATISM

  • MYOPIA

  • HYPEROPIA

  • PRESBYOPIA

  • RETINAL RIVALRY


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ASTIGMATISM

  • This condition is caused by an unequal curvature of the cornea or lens of the eye

  • Astigmatism is defined as the inability to focus different meridians simultaneously.

  • If, for example, astigmatics focus on power poles (vertical), the wires (horizontal) will be out of focus for most of them, as shown on the next slide.


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ASTIGMATISM


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VISUAL DEFICIENCIES

Myopia: Nearsightedness

Hyperopia: Farsightedness

Presbyopia: (aging)Hardening of lens, loss of elasticity


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RETINAL RIVALRY

  • This condition is caused when the eyes attempt to simultaneously perceive two dissimilar objects independent of each other.

  • Quite often the dominant eye will override the nondominant eye, possibly causing information to be missed.

  • This phenomenon may occur when pilots are viewing objects through the heads-up displays found in the optical systems of the AH-64.


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CORRECTIVE SURGERY

  • RADIAL KERATOTOMY

  • LASER IRIDOTOMY

  • PHOTO REFRACTIVE KERATECTOMY

  • LASER IN SITU KERATOMILEUSIS


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RADIAL KERATOTOMY

  • Flattening of the cornea by the creation of spoke like incisions

  • Performed to correct abnormal curvature of the cornea


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LASER IRIDOTOMY

  • A lazed opening of the iris to open ocular fluid passageways

  • Performed for the treatment of glaucoma

  • Creates artificial pupil (Lost peripheral vision non-correctable)


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PHOTO REFRACTIVE KERATECTOMY

(PRK)


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Laser in Situ Keratomileusis(LASIK)


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PHOTOPICVISION

  • Daylight or bright light

  • Central vision

  • Color sense and image sharpness

  • Visual acuity 20/20

  • Involves cones only


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MESOPIC VISION

MESOPIC VISION

  • Occurs at dawn, dusk and in full moonlight

  • Reduces color vision and decreases visual acuity

  • Involves both rods and cones

  • Greater emphasis should be placed on off-center vision as cones become less effective


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SCOTOPIC VISION

SCOTOPIC VISION

  • Occurs on dimly lit nights

  • Decreases visual acuity 20/200 or less

  • Causes loss of color perception

  • Causes night blind spot

  • Requires use of peripheral vision and recognition of objects by silhouettes

  • Involves the rods only


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BINOCULAR CUES

  • Valuable only when object is close

  • Each eye has a slightly different view

  • Operates subconsciously


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MONOCULAR CUES(GRAM)

  • Object seen as one picture

  • Are derived from experience

  • Subject to interpretation


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GEOMETRIC PERSPECTIVE

OBJECTS have different shapes when viewed at varying distances and altitudes


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GEOMETRIC PERSPECTIVES

Linear

perspectives

Apparent

foreshortening

Vertical position

in the field


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RETINAL IMAGE SIZE

  • Known size of objects

  • Increasing or decreasing size of objects

  • Terrestrial association

  • Overlapping contours


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5 Degrees

30 Ft

10 Degrees

KNOWN SIZE OF OBJECTS

1000 FT

30 Ft

500 FT


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DECREASE IN SIZE

INCREASE IN SIZE


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TERRESTRIAL ASSOCIATION

EYE


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OVERLAPPING CONTOURS


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AERIAL PERSPECTIVE

  • Distant information gained by clarity of object viewed or by the shadow it casts


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FADING OF COLORS AND

SHADES


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LOSS OF DETAIL OR TEXTURE


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LIGHTS AND SHADOWS


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MOTION PARALLAX

  • Very important cue to depth perception

    • Stationary objects

  • Rate depends on the distance of the object


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FLIGHT HAZARDS

  • SOLAR GLARE

  • BIRD STRIKES

  • LASERS

  • NERVE AGENTS


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SOLAR GLARE


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LASER

  • LASER

    Light

    Amplification by a

    Stimulated

    Emission of

    Radiation


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LASER

  • Intense, narrow beam of light, less than 1 inch in diameter

  • Widens with distance: 2km-diameter is 2 meter

2Meters

2 Km


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LASER INJURIES

  • Lens: Focuses and concentrates light rays entering the eye

  • Concentration of energy through the lens is intensified 100,000 times greater than the normal light entering the eye


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LASER INJURIES

  • Amount of damage depends on laser type, exposure time, and distance from the laser

  • Types of injuries:

    • Tiny lesions on the back of the eye

    • Flash blindness

    • Impaired night vision

    • Severe burns effecting vast body portions


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Hemorrhage

in to the vitreous

Multiple retinal laser burns


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Corneal burns

Subretinal hemorrhage


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Passive:

Take cover

NVD’S

Squinting

Protective goggles

Active:

Counter measures taught or directed

Evasive action

Scanning with one eye or monocular optics

LASER PROTECTIVE MEASURES


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NERVE AGENTS

  • Threat present both day and night at low level flight

  • Direct or minute exposure will cause miosis (pupil constriction)

  • Severity of miosis depends on agent concentration and cumulative effects of repeated exposure


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NERVE AGENT SYMPTOMS

  • Range from minimal to severe (dosage to eye?)

  • Severe miosis may persist for 48 hrs

  • Complete recovery may take up to 20 days

  • Consult flight surgeon immediately


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SELF-IMPOSED STRESSES

  • Drugs

  • Exhaustion

  • Alcohol

  • Tobacco

  • Hypoglycemia


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QUIZ

Click on the link below to access the

VISION IN AVIATION Quiz

http://ang.quizstarpro.com

Log-in and Click “Search” Tab

Class Name = VISION IN AVIATION


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SUMMARY


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