THE EYES

THE EYES

TERMINAL LEARNING OBJECTIVE

Action:Action: Eye Physiology Review Eye Physiology ReviewConditions:Conditions: While performing as an aircrew While performing as an aircrew

member.member.Standards :Standards : IAW FM 1-301, FM 8-2 and TC 1-204. IAW FM 1-301, FM 8-2 and TC 1-204.

ANATOMY AND PHYSIOLOGY OF THE HUMAN EYE

Cornea

Pupil

OPTICNERVE

Retina

Iris

Lens

Components of the EyeCorneaCornea - Transparent tissue located - Transparent tissue located over the front of the eye.over the front of the eye.IrisIris - Round, pigmented membrane - Round, pigmented membrane surrounding the pupil.surrounding the pupil.PupilPupil - Opening in the center of the - Opening in the center of the iris.iris.NOTENOTE: Pupil size.: Pupil size.

Components of the Eye (cont.)

LensLens - Transparent, biconvex - Transparent, biconvex membrane behind the pupil.membrane behind the pupil.

RetinaRetina - Thin multi-layered - Thin multi-layered membrane which covers most of the membrane which covers most of the

posterior compartment of the eye.posterior compartment of the eye.

Jacob’s Membrane

ConesCones - Allow you to identify color. - 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.

RodsRods - Allow you identify the outlines of - 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 SpotsDayDay - In the area of the optic disk caused by an - In the area of the optic disk caused by an absence of photoreceptor cells (rods and cones). absence of photoreceptor cells (rods and cones). 5-7.5 degree field. 5-7.5 degree field.

Night Night - Central viewing axis (fovea).- 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. 5-10 degree field.5-10 degree field.

BLIND SPOT

Types of Vision

Photopic visionPhotopic vision

Mesopic visionMesopic vision

Scotopic visionScotopic vision

Photopic vision Photopic VisionPhotopic Vision

Day light or bright light Central vision Color sense and sharp images Better visual acuity

LISTEN TO MIKE, WHILE YOU STUDY THE PICTURE.

Photopic vision

Photopic VisionPhotopic 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 moonlightDawn and dusk lighting & full moonlightParafoveal regionsParafoveal regions (rods and cones)(rods and cones)Decreased visual acuity and color visionDecreased visual acuity and color vision

Scotopic Vision

Night vision (partial moon & stars)Night vision (partial moon & stars)

Peripheral vision (rods only)Peripheral vision (rods only)

Acuity degraded 20/200 Acuity degraded 20/200 (color blind)(color blind)

Off center viewing to compensate Off center viewing to compensate blind spotblind spot

Limitations of Night Vision

Depth perceptionDepth perception Visual acuityVisual acuity Blind spotBlind spot Night adaptationNight adaptation Color visionColor vision

DEPTH PERCEPTION

VISUAL ACUITY, NIGHT

VISUAL ACUITY, DAY

COLOR VISION Photopic Mesopic Scotopic

NIGHT ADAPTATION

30 to 45 min. for complete adaptation.30 to 45 min. for complete adaptation.

Can take up to 3 to 5 hours if exposed Can take up to 3 to 5 hours if exposed to the glare of snow, water, or sun.to the glare of snow, water, or sun.

DARK ADAPTATION FACTORS

Photosensitivity of the eye.Photosensitivity of the eye.

Bleaching effect of rods and cones.Bleaching effect of rods and cones.

Effect of red light on rods.Effect of red light on rods.

Nutrition.Nutrition.

PROTECT NIGHT VISIONSunglasses (NV-Sunglasses (NV-

15)15)Adjust cockpit Adjust cockpit

lightslightsTurn off Turn off

exterior lightexterior lightClose one eyeClose one eye

Avoid brightly Avoid brightly lit areas.lit areas.

NutritionNutritionSupplemental Supplemental

oxygenoxygen

FLIGHT HAZARDS

Solar glareSolar glareBird strikeBird strikeLaserLaser

SOLAR GLARESOLAR GLARE

BIRD STRIKE

LASERSLASERS - light amplification by a LASERS - light amplification by a

stimulated emission of radiation.stimulated emission of radiation.

Very narrow beam of lightVery narrow beam of light

Widen with distanceWiden with distance

Severe injuries, burns of the eyesSevere injuries, burns of the eyes

Laser injury

SELF-IMPOSED STRESSES

DrugsDrugs

ExhaustionExhaustion

AlcoholAlcohol

TobaccoTobacco

Hypoglycemia (Health)Hypoglycemia (Health)

SCANNING TECHNIQUES

Stop-turn-stop-turn technique.Stop-turn-stop-turn technique.

Ten degree circular overlap.Ten degree circular overlap.

Off-center viewing.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 Valuable only when object is close.Valuable only when object is close. Each eye has a slightly different view.Each eye has a slightly different view.

MONOCULAR CUES

Object seen as one picture.Object seen as one picture. Are derived from experienceAre derived from experience

DISQUALIFYING MEDICAL/SURGICAL

PROCEDURES

Radial KerototomyRadial Kerototomy

PhotocoagulationPhotocoagulation

Laser iridotomyLaser iridotomy

RADIAL KERATOTOMY

Creates spoke like incisions on the cornea.Creates spoke like incisions on the cornea.Permanent disqualification for aviators.Permanent disqualification for aviators.

PHOTOCOAGULATION

Removal of protein by the Removal of protein by the controlled use of an intense beam controlled use of an intense beam of light.of light.

Treatment of retinal vessels or Treatment of retinal vessels or intraoculat masses.intraoculat masses.

LASER IRIDOTOMY

• Incision of the irisIncision of the iris

• Creation of an artificial pupilCreation of an artificial pupil

SUMMARY