THE EYES

TERMINAL LEARNING OBJECTIVE Ù Action: Eye Physiology Review Ù Conditions: While performing as an aircrew member.  Standards : IAW FM 1-301, FM 8-2 and TC

ANATOMY AND PHYSIOLOGY OF THE HUMAN EYE Cornea Pupil OPTIC NERVE Retina Iris Lens

Components of the Eye  Cornea - Transparent tissue located over the front of the eye. over the front of the eye.  Iris - Round, pigmented membrane surrounding the pupil. surrounding the pupil.  Pupil - Opening in the center of the iris. iris.  NOTE: Pupil size.

Components of the Eye (cont.)  Lens - Transparent, biconvex membrane behind the pupil.  Retina - Thin multi-layered membrane which covers most of the posterior compartment of the eye. posterior compartment of the eye.

Jacob’s Membrane  Cones - Allow you to identify color. Seven million with a 1: 1 ratio. Seven million with a 1: 1 ratio. Sharp visual acuity and color sense. Sharp visual acuity and color sense.  Rods - Allow you identify the outlines of shapes. 120 million with a 10,000: 1 shapes. 120 million with a 10,000: 1 ratio. More sensitive to light at night. ratio. More sensitive to light at night.

Detailed View of Rod & Cone Cells

CONES

RODS

Retinal Blind Spots  Day - In the area of the optic disk caused by an absence of photoreceptor cells (rods and cones). absence of photoreceptor cells (rods and cones) degree field degree field.  Night - Central viewing axis (fovea). Absence of rod cells. Absence of rod cells. Inability of cone cells to functions under low Inability of cone cells to functions under low ambient light conditions. ambient light conditions degree field degree field.

BLIND SPOT

Types of Vision nPhotopic vision nMesopic vision nScotopic vision

Photopic vision Photopic Vision n Day light or bright light n Central vision n Color sense and sharp images n Better visual acuity LISTEN TO MIKE, WHILE YOU STUDY THE PICTURE.

Photopic vision Photopic Vision  Day light or bright light  Central vision  Color sense and sharp images  Better visual acuity FOR THOSE OF YOU THAT ATTENDED THE BEACH FEST LAST WEEKEND.

Mesopic Vision  Dawn and dusk lighting & full moonlight  Parafoveal regions(rods and cones)  Decreased visual acuity and color vision

Scotopic Vision  Night vision (partial moon & stars)  Peripheral vision (rods only)  Acuity degraded 20/200 (color blind)  Off center viewing to compensate blind spot blind spot

Limitations of Night Vision n Depth perception n Visual acuity n Blind spot n Night adaptation n Color vision

DEPTH PERCEPTION

VISUAL ACUITY, NIGHT

VISUAL ACUITY, DAY

COLOR VISIONCOLOR VISION Photopic Mesopic Scotopic

NIGHT ADAPTATION n 30 to 45 min. for complete adaptation. n Can take up to 3 to 5 hours if exposed to the glare of snow, water, or sun.

DARK ADAPTATION FACTORS nPhotosensitivity of the eye. nBleaching effect of rods and cones. nEffect of red light on rods. nNutrition.

PROTECT NIGHT VISION nSunglasses (NV- 15) nAdjust cockpit lights nTurn off exterior light nClose one eye nAvoid brightly lit areas. nNutrition nSupplemental oxygen

FLIGHT HAZARDS nSolar glare nBird strike nLaser

SOLAR GLARE

BIRD STRIKE

LASERS nLASERS - light amplification by a stimulated emission of radiation. nVery narrow beam of light nWiden with distance nSevere injuries, burns of the eyes

Laser injury

SELF-IMPOSED STRESSES nDrugs nExhaustion nAlcohol nTobacco nHypoglycemia (Health)

SCANNING TECHNIQUES  Stop-turn-stop-turn technique.  Ten degree circular overlap.  Off-center viewing.

STOP-TURN-STOP-TURN SCANNING

View object by looking 10 degree above, below, or to either side. OFF-CENTER VIEWING

ASTIGMATISM

Visual Deficiencies Hyperopia (farsightedness) Myopia (nearsightedness)

CUES TO DEPTH PERCEPTION Binocular cues Monocular cues

BINOCULAR CUES nValuable only when object is close. nEach eye has a slightly different view.

MONOCULAR CUES nObject seen as one picture. nAre derived from experience

DISQUALIFYING MEDICAL/SURGICAL PROCEDURES nRadial Kerototomy nPhotocoagulation nLaser iridotomy

RADIAL KERATOTOMY nCreates spoke like incisions on the cornea. nPermanent disqualification for aviators.

PHOTOCOAGULATION nRemoval of protein by the controlled use of an intense beam of light. nTreatment of retinal vessels or intraoculat masses.

LASER IRIDOTOMY Incision of the irisIncision of the iris Creation of an artificial pupilCreation of an artificial pupil

SUMMARY