Visual fields and loss

Question 1

What can cause visual field loss?

Answer 1

Damage to:
Retina
Optic nerve
Chiasm
Optic tract
Optic radiation
Cortex

Question 2

What kind of visual loss does damage to the retina cause?

Answer 2

Horizontal (lose top or bottom)

Question 3

Where does vertical visual loss result from?

Answer 3

Optic nerve or posterior

Question 4

What kind of visual loss does an optic nerve lesion lead to?

Answer 4

Monocular blindness- all from 1 eye gone

Question 5

What kind of visual loss does an optic chiasm lesion lead to?

Answer 5

Bitemporal hemianopsia- lose peripheral fields

Question 6

What kind of visual loss does an optic tract lesion lead to?

Answer 6

Contralateral hemianopia/Homonymous hemianopsia- lose same side

Question 7

What kind of visual loss does an optic radiation lesion lead to?

Answer 7

Quadrant Hemianopsia- just lose quarter on same side

Question 8

What kind of visual loss does a cortex lesion lead to?

Answer 8

Bitemporal Hemianopia with foveal sparing

Question 9

Why do you get foveal sparing with a cortex lesion?

Answer 9

Due to number of fibres going from fovea to cortex meaning affecting all is hard

Question 10

What can lead to damage of the optic nerve, chiams, tract, radiations or cortex?

Answer 10

Vascular disease
Space occupying lesion
Demyelination
Trauma
Neuritis

Question 11

How does neuritis progress?

Answer 11

Progressive unilateral visual loss
Colour desaturation (colours appear washed out)
Gradual recovery

Question 12

Describe the visual pathway

Answer 12

Light strikes retina
Retina becomes optic nerve
Nasal portion of optic nerves cross at chiasm
Optic nerves become optic tract at chiasm
Optic tract becomes optic radiations at Lateral Geniculate Nucleus
Optic tracts go north and south to visual cortex

Question 13

What is the term for a normal eye?

Answer 13

Emmetropic

Question 14

Describe the focus of the lens

Answer 14

Light diverges from point
Further away point light diverges more therefore requires thinner lens with greater angle to focus on retina
Closer light diverges less therefore requires thicker lens with less angle to focus on retina

Question 15

What does a convex lens do?

Answer 15

Focus light down

Question 16

What does a concave lense do?

Answer 16

Spread light out

Question 17

What is a myopic eye?

Answer 17

Nearsighted- eyeball is too big to focus distant light on retina

Question 18

Why can’t a myopic eye focus distant light?

Answer 18

Lens is too thick therefore light exits with a smaller angle and focuses in posterior chamber

Question 19

What is a hyperopic eye?

Answer 19

Longsited- eyeball too small to focus near light on retina

Question 20

Why can’t a hyperopic eye focus near light?

Answer 20

Lens is too thin therefore light exits with a larger angle and focuses behind eye

Question 21

What kind of lens can help in myopia?

Answer 21

Concave back

Question 22

Why can a concave lens help in myopia?

Answer 22

Diverges light more therefore enters and exits lens with greater angle

Question 23

What kind of lens can help in hyperopia?

Answer 23

Convex front

Question 24

Why can a convex lens help in hyperopia?

Answer 24

Focuses light down so enters and exits with less angle

Question 25

How big is a normal eyeball?

Answer 25

~22mm

Question 26

How big is a myopic eyeball?

Answer 26

~33mm

Question 27

How big is a hyperopic eyeball?

Answer 27

~18mm

Question 28

A lesion to which lobe of the brain will give a top field loss?

Answer 28

Temporal

Question 29

A lesion to which lobe of the brain will give a bottom field loss?

Answer 29

Parietal