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THE VISUAL SYSTEM IN FLIGHT

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  1. THE VISUAL SYSTEM IN FLIGHT

  2. 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

  3. 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.

  4. ANATOMY OF THE HUMAN EYE CORNEA

  5. ANATOMY OF THE HUMAN EYE IRIS

  6. ANATOMY OF THE HUMAN EYE PUPIL

  7. 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.

  8. ANATOMY OF THE HUMAN EYE LENS

  9. ANATOMY OF THE HUMAN EYE RETINA

  10. ANATOMY OF THE HUMAN EYE FOVEA CENTRALIS

  11. 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)

  12. 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)

  13. 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

  14. 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

  15. ANATOMY OF THE HUMAN EYE OPTIC DISK

  16. ANATOMY OF THE HUMAN EYE PARAFOVEAL REGIONS

  17. ANATOMY OF THE HUMAN EYE PERIPHERAL REGIONS

  18. VISUAL DEFICIENCIES • ASTIGMATISM • MYOPIA • HYPEROPIA • PRESBYOPIA • RETINAL RIVALRY

  19. 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.

  20. ASTIGMATISM

  21. VISUAL DEFICIENCIES Myopia: Nearsightedness Hyperopia: Farsightedness Presbyopia: (aging)Hardening of lens, loss of elasticity

  22. 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.

  23. CORRECTIVE SURGERY • RADIAL KERATOTOMY • LASER IRIDOTOMY • PHOTO REFRACTIVE KERATECTOMY • LASER IN SITU KERATOMILEUSIS

  24. RADIAL KERATOTOMY • Flattening of the cornea by the creation of spoke like incisions • Performed to correct abnormal curvature of the cornea

  25. 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)

  26. PHOTO REFRACTIVE KERATECTOMY (PRK)

  27. Laser in Situ Keratomileusis(LASIK)

  28. PHOTOPICVISION • Daylight or bright light • Central vision • Color sense and image sharpness • Visual acuity 20/20 • Involves cones only

  29. 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

  30. 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

  31. BINOCULAR CUES • Valuable only when object is close • Each eye has a slightly different view • Operates subconsciously

  32. MONOCULAR CUES(GRAM) • Object seen as one picture • Are derived from experience • Subject to interpretation

  33. GEOMETRIC PERSPECTIVE OBJECTS have different shapes when viewed at varying distances and altitudes

  34. GEOMETRIC PERSPECTIVES Linear perspectives Apparent foreshortening Vertical position in the field

  35. RETINAL IMAGE SIZE • Known size of objects • Increasing or decreasing size of objects • Terrestrial association • Overlapping contours

  36. 5 Degrees 30 Ft 10 Degrees KNOWN SIZE OF OBJECTS 1000 FT 30 Ft 500 FT

  37. DECREASE IN SIZE INCREASE IN SIZE

  38. TERRESTRIAL ASSOCIATION EYE

  39. OVERLAPPING CONTOURS

  40. AERIAL PERSPECTIVE • Distant information gained by clarity of object viewed or by the shadow it casts

  41. FADING OF COLORS AND SHADES

  42. LOSS OF DETAIL OR TEXTURE

  43. LIGHTS AND SHADOWS

  44. MOTION PARALLAX • Very important cue to depth perception • Stationary objects • Rate depends on the distance of the object

  45. FLIGHT HAZARDS • SOLAR GLARE • BIRD STRIKES • LASERS • NERVE AGENTS

  46. SOLAR GLARE

  47. LASER • LASER Light Amplification by a Stimulated Emission of Radiation

  48. LASER • Intense, narrow beam of light, less than 1 inch in diameter • Widens with distance: 2km-diameter is 2 meter 2Meters 2 Km

  49. 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