TYPES OF VISION PHOTOPIC Cones only Daylight or high artificial light illumination Sharp images and color vision Use of central vision MESOPIC Rods and cones Dawn, dusk, and full moon Color vision reduced and visual acuity decreased SCOTOPIC Rods only Low light levels Decreased visual acuity (20/200 or <) Loss of color perception Night blind spot Use peripheral vision

Photopic vision PHOTOPIC VISION n Day light or bright light n Central vision n Color sense and sharp n Better visual acuity

MESOPIC VISION n Dawn and dusk n Parafoveal regions (rods and cones) n Decrease visual acuity

SCOTOPIC VISION n Night vision n Peripheral vision (rods only) n Acuity degraded 20/200 color blind n Off center viewing to compensate blind spot

DARK ADAPTATION Process which eyes increase sensitivity to low levels of illumination. Increase rodopsin levels in the rods Varies in degree and rate The lower the light level the more rapid dark adaptation Maximum level in about 30 to 45 minutes Rods can become as much as 10,000 times more sensitive 2-3 Minutes after wearing NVG’s if previously dark adapted NIGHT VISION PROTECTION Sunglasses Oxygen Airfield lighting High-intensity lighting Lights in built-up areas Flares Weapon flashes

PROTECT NIGHT VISION n Sunglasses n Adjust cockpit light lowest readable level n Turn off exterior light n Close on eye n Supplemental oxygen

DAY AND NIGHT BLIND SPOT DAY BLIND SPOT ( physiological blind spot ) Lack of photosensitive cells on the optic disk Present all the time Covers an area of 5.5 to 7.5 degrees Compensated for by overlapping binocular vision NIGHT BLIND SPOT Concentration of cones in the fovea centralis and parafovea Present in low illumination levels Covers an area of 5 to 10 degrees Central vision affected Binocular vision can not compensate

BLIND SPOT

CUES TO DEPTH PERCEPTION Binocular cues Monocular cues

BINOCULAR CUES n Valuable only when object is close. n Each eye has a slightly different view.

MONOCULAR CUES n Object seen as one picture. n Are derived from experience

DISTANCE ESTIMATION and DEPTH PERCEPTION GEOMETRIC PERSPECTIVE Linear perspective Apparent foreshortening Vertical position in the field RETINAL IMAGE SIZE Known size of an object Increasing or decreasing size of objects Terrestrial association Overlapping contours AERIAL PERSPECTIVE Variations of colors and shades Loss of detail and texture Position of light source and direction of shadow MOTION PARALLAX Relative movement of stationary objects

LINEAR PERSPECTIVE Parallel lines tend to converge.

APPARENT FORESHORTENING The shape of object appears elliptical

VERTICAL POSITION IN THE FIELD Objects appear to be higher on the horizon.

n Known size of objects. n Increasing of decreasing size of objects. n Terrestrial association. n Overlapping contours.

INCREASING OR DECREASING SIZE OF AND OBJECT Increase in size Decrease in size

TERRESTRIALASSOCIATION

OVERLAPPING CONTOURS

AERIAL PERSPECTIVE n Fading colors or shades. n Loss of detail of texture. n Position of light source.

VARIATIONS IN COLOR AND SHADE n Objects viewed through haze, fog and smoke. n Transmission of light.

LOSS OF DETAIL OR TEXTURE

POSITION OF LIGHT SOURCE AND DIRECTION OF SHADOW

MOTION PARALLAX n Very important cue. n Relative motion. n Depends on the distance of the object.

VISUAL ILLUSIONS

RELATIVE MOTION ILLUSION n Motion between you and a moving object. n Confusing as to who is moving.

GROUND LIGHTS MISINTERPRETATION n Misinterpretation of lights

DEPTH PERCEPTION ILLUSION n Flying over sand, snow, or water. n Flying through haze, smoke, or fog.

STRUCTURAL ILLUSION n Curved glass, heat waves, rain, snow, sleet, or other disturbance. n Disturbance/distortion.

AUTOKINETIC ILLUSION n Lack of visual references. n Off center vision and scanning pattern. n Occurs 8-10 seconds

SIZE DISTANCE u False perception of distance from an object on the ground or in the air. u Misinterprets an unfamiliar object’s size to be the same as an object they are normally accustomed to viewing.

FLICKER VERTIGO n Light flickers at a rate of 4 to 20 cycles per second. n May cause nausea, vomiting convulsions and unconsciousness.

FASCINATION/FIXATION u Pilot intent on hitting target. u Pilot forgets to fly aircraft. u Fly into target or ground.

REVERSIBLE PERSPECTIVE ILLUSION n Happens at night. n An aircraft flying parallel to yours. n Corrective actions. n Observe the aircraft lights.

ALTERED PLANES OF REFERENCES n Approaching a line of clouds or mountains. n Climb in altitude. n Tend to tilt away from the clouds.

USE OF INTERNAL AND EXTERNAL LIGHTS  Use only blue-green instrument and supplemental lighting  Ensure internal lighting does not degrade vision through the reflection off of the windshield  Use of external lighting may degrade the NVG’s, turn off all lights not required by regulations

NIGHT MYOPIA Distant objects not clearly seen Blue-green light causes blurred vision As pupil diameter increases image sharpness decreases Can be corrected with prescription lenses ASTIGMATISM Irregular shape of the cornea Causes out of focus condition Inability to focus on different meridians simultaneously PRESBYOPIA Normal aging process Lens hardens Lose ability to focus on near by objects Can be corrected with certain types of bifocal spectacles VISUAL LIMITATIONS

ASTIGMATISM

VISUAL DEFICIENCIES Hyperopia (farsightedness) Myopia (nearsightedness)

FACTORS AFFECTING DARK ADAPTATION

SCANNING TECHNIQUES SCAN Begin at the greatest distance an object can be seen and move inward Look left to right or right to left Use stop turn motion Scan area 30 degrees wide each stop View no longer than 2-3 seconds Overlap previous field by 10 degrees OFF CENTER VIEWING Limitation of central vision at night Maintain observation with peripheral vision Steady fixation of.5 to 1 second achieves maximum sensitivity Objects viewed longer than 2 to 3 seconds become one solid tone

degrees

n n VISUAL ACUITY (20-40 / Por) n n MAGNIFICATION (1X) n n INTENSITY ( ) n n FIELD OF VIEW (40 DEG) n n POWER SOURCE (2AA or 3V Lithium) n n LOW VOLTAGE INDICATOR (30 min) n n CRASH BREAKAWAY (10-15G) n n FOCUS (28cm +/- 3 to Infinity) ANVIS CHARACTERISTICS

MONOCULAR COMPONENTS *

n nNEEDS SOME LUMINATION n nBRIGHT LIGHTS n nTUNNEL VISION n nPOOR DEPTH PERCEPTION n nCOLOR DISCRIMINATION n nINABILITY TO DETECT FOG ANVIS LIMITATIONS

n n SHADING n n EDGE GLOW n n FLASHING, FLICKERING OR INTERMITTENT OPERATIONS OPERATIONAL DEFECTS

SHADING

EDGE GLOW

FLASHING, FLICKERING OR INTERMITTENT OPERATIONS

n n BRIGHT SPOTS / EMISSION POINTS n n BLACK SPOTS n n CHICKEN WIRE n n IMAGE DISTORTION n n FIXED PATTERN NOISE n n IMAGE DISPARITY n n OUTPUT BRIGHTNESS VARIATION COSMETIC BLEMISHES

BRIGHT SPOTS / EMISSION POINTS

BLACK SPOTS

CHICKEN WIRE

IMAGE DISTORTION

FIXED-PATTERN NOISE

IMAGE DISPARITY

OUTPUT BRIGHTNESS VARIATION

NERVE AGENTS n Effects on night vision. n Miosis (pupils will not dilate in low ambient light). n Minimal to severe symptoms. n Recovery may take up to 20 days. n Insidious onset.

LASERS n Type of laser. n The energy output. n Exposure time. n Distance from the laser.

LASERS n LASERS - light amplification by a stimulated emission of radiation. n Very narrow beam of light. n Progressively wider with distance. n May cause severe injuries, burning of the eyes.

MILITARY LASERS n At 1 kilometer, the beam is 1 meter in diameter. At 2 kilometers the beam is 2 meters in diameter. n Can irradiate the whole body. n Can burn clothing. n Most are not powerful enough to burn.

PROTECTION AGAINST LASER INJURY n Passive measures. n Active measures.

PASSIVE MEASURES n Take cover n Protective gear l Protective Goggles B-LPS l NVD n Squinting

PHYSIOLOGY OF THE EYE