Visual fields and loss Flashcards Preview

Ophthalmology > Visual fields and loss > Flashcards

Flashcards in Visual fields and loss Deck (29)
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1
Q

What can cause visual field loss?

A
Damage to:
Retina
Optic nerve
Chiasm
Optic tract
Optic radiation
Cortex
2
Q

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

A

Horizontal (lose top or bottom)

3
Q

Where does vertical visual loss result from?

A

Optic nerve or posterior

4
Q

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

A

Monocular blindness- all from 1 eye gone

5
Q

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

A

Bitemporal hemianopsia- lose peripheral fields

6
Q

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

A

Contralateral hemianopia/Homonymous hemianopsia- lose same side

7
Q

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

A

Quadrant Hemianopsia- just lose quarter on same side

8
Q

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

A

Bitemporal Hemianopia with foveal sparing

9
Q

Why do you get foveal sparing with a cortex lesion?

A

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

10
Q

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

A
Vascular disease
Space occupying lesion
Demyelination
Trauma
Neuritis
11
Q

How does neuritis progress?

A

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

12
Q

Describe the visual pathway

A

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

13
Q

What is the term for a normal eye?

A

Emmetropic

14
Q

Describe the focus of the lens

A

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

15
Q

What does a convex lens do?

A

Focus light down

16
Q

What does a concave lense do?

A

Spread light out

17
Q

What is a myopic eye?

A

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

18
Q

Why can’t a myopic eye focus distant light?

A

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

19
Q

What is a hyperopic eye?

A

Longsited- eyeball too small to focus near light on retina

20
Q

Why can’t a hyperopic eye focus near light?

A

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

21
Q

What kind of lens can help in myopia?

A

Concave back

22
Q

Why can a concave lens help in myopia?

A

Diverges light more therefore enters and exits lens with greater angle

23
Q

What kind of lens can help in hyperopia?

A

Convex front

24
Q

Why can a convex lens help in hyperopia?

A

Focuses light down so enters and exits with less angle

25
Q

How big is a normal eyeball?

A

~22mm

26
Q

How big is a myopic eyeball?

A

~33mm

27
Q

How big is a hyperopic eyeball?

A

~18mm

28
Q

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

A

Temporal

29
Q

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

A

Parietal