Eyes

Question 1

Visual System Composed Of

Answer 1

Eye
Optic Nerve
Visual Cortex

Question 2

Visual System Composed Of

Answer 2

Eye
Optic Nerve
Visual Cortex

Question 3

What keeps spherical shape of eye

Answer 3

Two fluids

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

Supply nutrients to eye

Question 4

Retina

Answer 4

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

Question 5

Lens

Answer 5

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

Question 6

Pupil

Answer 6

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

Question 7

Cornea

Answer 7

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

Question 8

Iris

Answer 8

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

Question 9

BLIND SPOT

Answer 9

No Photoreceptors in optic nerve (optic disk)

Question 10

Cones - primary vision role/where they are found

Answer 10

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

Question 11

Visual Acuity + figures away from fovea

Answer 11

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

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

Question 12

Rods

Answer 12

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

Question 13

Visual Field

Answer 13

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

120 degree to right
150 degrees up and down

Question 14

Movement of eye to track and pursuit

Answer 14

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

Question 15

Factors effecting visual acuity

Answer 15

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

Question 16

Binocular vision

Answer 16

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

Question 17

Non stereoscopic cues

Answer 17

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

Question 18

Monocular Vision

Answer 18

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

Question 19

Dark adaptation

Answer 19

Cones = 7-9 minutes
Rods = 30 minutes

Lost if exposed to bright light

Question 20

Light adaptation

Answer 20

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

Question 21

Flash Blindness

Answer 21

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

Question 22

Hazards of light at high alt

Answer 22

Blue and UV light (cumulative damage)

Question 23

Good and bad quality’s of sunglasses

Answer 23

Dos:
High quality
Strong polycarbonate
Thin rims
Good optical qualities

Do Not:
Photochromic sunglasses
Polarised
Yellow tinted

Question 24

Empty Field Myopia

Answer 24

Default to objects 1-2m ahead
Cloudless featureless sky

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

Question 25

Detecting objects in dark

Answer 25

Look at them slightly off centre Scotopic vision used

Question 26

Refractive Error Long Sightedness (Hypermetropia)

Answer 26

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

Question 27

Refractive error - Short sightedness Myopia

Answer 27

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

Question 28

Astigmatism

Answer 28

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

Question 29

Rules for spectacles and contact lenses

Answer 29

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

Question 30

Presbyopia

Answer 30

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

Question 31

Glaucoma

Answer 31

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

Question 32

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

Answer 32

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

Question 33

Order of light passing through components in the human eye

Answer 33

Cornea/Iris/Pupil/Lens/Retina Remember alphabetic order

Question 34

What controls accomodation

Answer 34

Lens

Question 35

What controls adaption

Answer 35

Pupil

Question 36

Monocular cues for depth perception include

Answer 36

Obcuration Texture Atmospheric perspective