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Human Performance > Eyes > Flashcards

Eyes Flashcards

1
Q

Visual System Composed Of

A

Eye
Optic Nerve
Visual Cortex

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2
Q

Visual System Composed Of

A

Eye
Optic Nerve
Visual Cortex

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3
Q

What keeps spherical shape of eye

A

Two fluids

  • Aqueous Humour (front of eye)
  • Vitreous humour (back of eye)

Supply nutrients to eye

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4
Q

Retina

A

Inner lining of the eye containing light sensitive cells (photoreceptors)

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5
Q

Lens

A

20/40% of focusing occurs here
Ciliary muscles change lens shape for accomodation
Ageing/fatigue impact ciliary muscles

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6
Q

Pupil

A

Hole in Iris
Contracts if too much light
Expands when not enough light

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7
Q

Cornea

A

Allows light to enter via the pupil
60/80% of focusing occurs here
O2 needed to keep moisture

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8
Q

Iris

A

Colour part of eye
Contract and expands to maintain constant level of light

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9
Q

BLIND SPOT

A

No Photoreceptors in optic nerve (optic disk)

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10
Q

Cones - primary vision role/where they are found

A

Primary vision in daylight
Colour vision (red, blue and green)
Key for central vision

Photopic (light seeing)
Central vision (visual acuity)
150,000 cones per mom
Found around fovea

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11
Q

Visual Acuity + figures away from fovea

A

Capacity of the eye to resolve detail
More photoreceptors greater the acuity

5 degree away from fovea = 1/2
25 degrees away = 1/10

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12
Q

Rods

A

Peripheral vision
Concentrated along retina
Black and white night vision
Scotopic vision
Sensitive to movement

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13
Q

Visual Field

A

Defined as the space which can be seen at any time by a stationery eye

120 degree to right
150 degrees up and down

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14
Q

Movement of eye to track and pursuit

A

6 extra ocular muscles
Saccade - sudden jerk
Attention - moving eye to place over fovea
Track - Smooth pursuit movements

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15
Q

Factors effecting visual acuity

A

Angular distance from fovea
Level of lighting (dark condition cones not functioning as well)
Distance of object

Age/disease
Hypoxia
Smoking
Medication
Short/long sightedness

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16
Q

Binocular vision

A

Gives stereoscopic vision (Judging close objects)
Estimate distance using two eyes effective to about 60m out

17
Q

Non stereoscopic cues

A

Estimating the distance after being further out than binocular vision
Using:
Colour
Contrast
Size
Rate of movement

18
Q

Monocular Vision

A

Loss of all depth perception of close objects
Does not affect depth perception far away
Struggle to catch a ball

Initial examination class 1 - seen as unfit
Revalidation - referred and then assessed for fitness

19
Q

Dark adaptation

A

Cones = 7-9 minutes
Rods = 30 minutes

Lost if exposed to bright light

20
Q

Light adaptation

A

Eyelids will close
Pupil to contract
10 seconds for photoreceptors to adapt

21
Q

Flash Blindness

A

Sudden intense light causing degradation in vision temporarily
Can bleach photoreceptors and cause vision damage

22
Q

Hazards of light at high alt

A

Blue and UV light (cumulative damage)

23
Q

Good and bad quality’s of sunglasses

A

Dos:
High quality
Strong polycarbonate
Thin rims
Good optical qualities

Do Not:
Photochromic sunglasses
Polarised
Yellow tinted

24
Q

Empty Field Myopia

A

Default to objects 1-2m ahead
Cloudless featureless sky

Regular eye movements overlapping sectors of about 10 degrees
Focus on objects at distant

25
Q

Detecting objects in dark

A

Look at them slightly off centre
Scotopic vision used

26
Q

Refractive Error Long Sightedness
(Hypermetropia)

A

Distance objects clear
Closed objects blurred
Convex len used to fix
Light focuses behind the retina

27
Q

Refractive error - Short sightedness
Myopia

A

Close objects clear
Distant objects blurry
Corrected with concave lens
Light focuses in front of the retina

28
Q

Astigmatism

A

Misshapen cornea/lens
Difficulty in resolving detail
Corrected by tailored lens

29
Q

Rules for spectacles and contact lenses

A

Must have easy access spare at all times

Contact lenses can be worn for distant vision ONLY and no bi-focal lenses not permitted with contact lenses

30
Q

Presbyopia

A

Longsightedness by age
Lens less flexible/elasticity of ciliary muscles reduces
Decrease in accomodation

31
Q

Glaucoma

A

High pressure in the eye
Retinal blood supply cuts causing retinal cell death
Blindness

Sudden and painful - fine jet of pressurised air onto cornea measuring the deflection

32
Q

What happens if you are in darkness for a long time and exposed to bright light

A

Dark adaptation and will hamper depth perception will take time to adapt to high brightness levels

33
Q

Order of light passing through components in the human eye

A

Cornea/Iris/Pupil/Lens/Retina

Remember alphabetic order

34
Q

What controls accomodation

A

Lens

35
Q

What controls adaption

A

Pupil

36
Q

Monocular cues for depth perception include

A

Obcuration
Texture
Atmospheric perspective

Human Performance (18 decks)

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