The eye and vision; visual pathways Flashcards by Olivia Mooney

What are the three parts of the visual system?

Eyeball - optical front end and retina/optic disk at the back
Connections - optic nerve, optic chiasm, optic tract, LGM, optic radiations
Brain - occipital, temporal, frontal and parietal lobes

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What is the most common refractive error?

Presbyopia

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Define presbyopia

gradual loss of your eyes ability to focus on near by objects

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Define myopia

can see objects near to your clearly, but objects further away are blurry

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What is the lens correction for myopia?

CONCAVE (minus) lenses

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Define hypermetropia

nearby ojects are blurred, but vision is clearer when looking at objects further away

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What is the lens correction for hypermteropia?

convex lens

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What is the retina?

layer at the back of the eye that contains cells sensitive to light

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What are the two types of cells in the retina?

rods and cones

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What are the main features of rod cells

120 million onretina
high convergence to ganglion cells
greyscale vision
very light sensitive
widespread distribution
broad spectral senstivity

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What are the main features of cone cells?

6 trillion in retina
lower convergence to ganglion cells
colour vision (red, green, blue)
1/30th of sensitivity of rods
concentrated in the macula
narrow spectral sensitivity

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What is the consequence to vision if the right optic nerve was severed?

Loss of sight in the right eye only

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What is the consequence to vision if there is damage at the optic chiasm

bitemporal hemiaponia

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What is the consequence to vision if there is temporal lobe damage

superior quadrantanopia

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What is the consequence to vision if there is damage to the parietal lobe?

Inferior quadrantanopia

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What is the consequence to vision if there is damage to the right occiptal lobe

left hemianopia

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Describe the WHAT (ventral) stream

running through the temporal lobes; tells you what the thing is

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Where is the visual library of the brain?

temporal lobes

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Describe the where stream of the brain

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going through the parietal lobes. Appraises the overall visual scene and allows the brain to see one thing amongst many

Where is the attention centre of the brain

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parietal lobes

Where is the action based vision centre of the brain

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frontal lobe

excecutes a plan based on what it has seen

What is simultanagnosia and what causes it?

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diffuclty finding one thing amongst many

bilateral parietal brain damage

What is achromatopsia? And what causes it?

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unable to see in colour

bilateral anterior occipital brain damage

Define visual acuity

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the ability of the vision system to resolve (‘see’) a gap between two points. This is known as spatial resolution

What are the two main types of sight impairment?

* Sight impairment (SI) * Severe signt impairment (SSI)

RAPD --\>

Relative Afferent Pupillary Defect A condition in which the pupils respond differently to light stimuli shone in one eye at a time due to unilateral or asymmetrical disease of the retina or optic nerve

What are the causes of RAPD?

- Optic neuritis - Anterior ischaemic optic neuropathy (AION) - Tumour pressing on the optic nerve - Glaucoma

What is opacity in the eyes?

stops light passing through the cornea to the retina and may cause the cornea to appear white/clouded over

What is the retinal reflection test?

"RED REFLEX" When light passes through the pupil and is reflected back of the retina to a viewing aperture, creating a red glow \*blue in black people\*

What can the retinal reflection test identify?

* corneal scar * cataract * retinoblastoma

Leukocoria =

"white pupil" when the pupil is white rather than black

What are the key elements to obserbe when examining the optic nerve?

Margin, colour and cup

What are the causes of a swollen optic disc?

* Pseudo swelling * Small discs * Calcium deposits ‘drusen’ * Genuine swelling * Optic Neuritis (VA reduced) * Raised ICP (VA normal) * SOL * IIH * Hydrocephalus

What extra-ocular eye muscle(s) are supplied by: CN IV

Superior oblique

What extra-ocular eye muscle(s) are supplied by: CN III

* inferior rectus * inferior oblique * superior rectus * medial rectus

What extra-ocular eye muscle(s) are supplied by: CN VI

Lateral rectus

Features of 3rd CNP

* Vertical diplopia * Eye is “down and out” * Diplopia every where * Pupil dilated and ptosis * Can be associated with aneurysm – needs urgent brain imaging and angiogram

Features of 4th CNP

* Oblique diplopia * Head tilt away from side of the lesion * Diplopia worse away from the side of the palsy if unilateral (adduction) * Common after head injury * Bilateral – might be congenital

Features of 6th CNP

* Horizontal diplopia * Worse in far distance * Worse towards the side of the palsy if unilateral * Bilateral – concerned that raised intracranial pressure is present