- Transmission of light - Refraction - Dehydrate endothelium (no repair) - the innermost layer of the cornea, maintain corneal clarity by pumping water out (since water molecules alter the regular spacing between collagen fibres & cause opacity) - Surface Epithelium (capable of repair)- outer layer of the eye, many layers that slough off and are constantly regenerated

- Forms the white capsule around the eye, except at its anterior surface where its specialised into clear cornea - Offers protection; formed of a tough outer layer of collagen - Serves as an insertion point for the external muscles of the eye - Continuation of dura mater and cornea

- Specialsed section of choroid - Contains and controls the size of the pupil - which lets light in - Sphincter muscles (circular fibres) make the pupil smaller (parasympathetic) - Dilator muscles (radial fibres) make the pupil larger (sympathetic) - Gives eyes their colour

- Important for the nutrition of the outer retina (photoreceptors) - Acts as a heat sink - Darkly pigmented so that it can absorb stray photons

- Produces vitreous humour: which acts as a collagen scaffold, helps maintain intraocular pressure and is important in the transmission of light

Visual System Flashcards by Sara Salman

Three coats of eye

Outer
Middle (Uvea)
Inner

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Function of cornea

Transmission of light
Refraction
Dehydrate endothelium (no repair) - the innermost layer of the cornea, maintain corneal clarity by pumping water out
(since water molecules alter the regular spacing between collagen fibres & cause opacity)
Surface Epithelium (capable of repair)- outer layer of the eye, many layers that slough off and are constantly regenerated

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Function of Sclera

Forms the white capsule around the eye, except at its anterior surface where its specialised into clear cornea
Offers protection; formed of a tough outer layer of collagen
Serves as an insertion point for the external muscles of the eye
Continuation of dura mater and cornea

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Function of Iris

Specialsed section of choroid
Contains and controls the size of the pupil - which lets light in
Sphincter muscles (circular fibres) make the pupil smaller (parasympathetic)
Dilator muscles (radial fibres) make the pupil larger (sympathetic)
Gives eyes their colour

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Function of Ciliary body

Glandular epithelium - produces: aqueous humour and nutrients for cornea and lens
Aqueous humour : mainly water and electrolytes, located in the interior chamber - important in maintaining intraocular pressure (15mmHg)
accommodation;
the adjustment of the lens in the eye so that clear images of objects at different distances are formed on the retina

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Where does ciliary body receive innervation from

parasympathetic system

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What is the ciliary body made from and why

smooth muscle which controls accommodation;

the adjustment of the lens in the eye so that clear images of objects at different distances are formed on the retina

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Function of Choroid

Important for the nutrition of the outer retina (photoreceptors)
Acts as a heat sink
Darkly pigmented so that it can absorb stray photons

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Function of Retina

Produces vitreous humour: which acts as a collagen scaffold, helps maintain intraocular pressure and is important in the transmission of light

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How is the retina involved in the transmission of light

Light passes though the pupil from the visual field to project an image on the retina.

An object that attention is focused on, projects an image that is centred near the posterior pole of the eye along the visual axis, this point is known as the FOVEA CENTRALIS and the surrounding 1cm is known the MACULA LUTEA at these points the retina is specially modified for maximal visual acuity (resolving power)

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Why is there a ‘blind spot’

Medial to macula there is region where retinal axons accumulate to leave the eye - this is the optic disc (where optic nerve forms) - no photoreceptors here = blind spot

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whats RPE

RETINAL PIGMENT EPITHELIUM

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What does RPE do

contains photoreceptors (rods&cones) so it is able to convert light into electric impulses (PHOTOELECTRIC TRANSDUCER) which are transmitted to ganglion cells which go on to make optic fibres an eventually the optic nerve

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Rods

Important to vision in dim lighting - v sensitive to light

also important for peripheral vision

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cones

colour vision

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Tear film 3 layers:

1 ANTERIOR LIPID (oils) - secreted by meibomium glands, provides a hydrophobic barrier to prevent the aqueous layer evaporating

2 MIDDLE AQUEOUS (water, electrolytes & proteins) - secreted by lacrimal glands, regulates transport though the cornea and prevent infection

3 POSTERIOR MUCUS - secreted by goblet cells, provides a hydrophilic layer that allows for the even distribution of the tear film

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ANTERIOR LIPID (oils) - secreted by

meibomium glands

provides a hydrophobic barrier to prevent the aqueous layer evaporating

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MIDDLE AQUEOUS (water, electrolytes & proteins) - secreted by and does what

lacrimal glands

regulates transport though the cornea and prevent infection

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POSTERIOR MUCUS - secreted by an does what

goblet cells

provides a hydrophilic layer that allows for the even distribution of the tear film

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Layers through which a photon must travel though the eye (12)

1) Tear film (transmission)
2) Cornea (transmission and refraction - contributes o 2/3 of refraction)
3) Aqueous humour - T
4) Lens - T&R
5) Vitreous humour - T
6) Ganglion Cell -T
7) Amacrine cell - T
8) Bipolar cell - T
9) Horizontal cell - T
10) Cone - Transduction
11) Rods - Tranduction
12) Pigmented epithelium - absorption of excess photons

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What divisions of the internal carotid artery supply the eye

Ophthalmic artery 
Central Retinal artery (which passes into optic nerve)
ciliary artery 
lacrimal 
ethmoid 
eyelid artery

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What divisions of the external carotid artery supply the eye

Facial Artery - supplies medial lid and orbit

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Where is info from the eyes transmitted to?

Primary Visual cortex of occipital lobe

What fields does eye receive info from

Temporal and nasal

Where is primary visual cortex located

- occipital lobe | - Medial surface of the hemisphere in the region above and below the calcarine sulcus

function of the visual association cortex

concerned with interpretation of visual images, recognition, depth perception and colour vision

The optic nerve carries the axons of the cells in the what layer of the retina where do they leave the orbit

Ganglionic layer leave the orbit bilaterally via the optic canal to enter the cranial cavity

Where is the optic chiasm located

just anterior to the PITUITARY INFUNDIBULUM

What do the fibres from nasal portion of the retina carry what visual fields

temporal visual fields

fibres from the temproral portion of the retina carry what \ visual fields

nasal visual fields

where do the optic tracts carry the fibres to terminate

posterolaterally around the cerebral peduncles to terminate at the lateral geniculate bodies of the thalamus

Where do optic radiations go after the lateral geniculate body

Split into two 1 the fibres carrying information from the inferior portions of he retina (n thus superior visual fields) travel by looping laterally though the temporal lobe to the visual cortex known as MEYERS LOOP 2 Fibres carrying info from Superior portions of the retina (=inferior visual field) travel by looping superiorly through the Parietal lobe into the visual cortex known at BAUMS LOOP

To remember = I'MAuditory

Inferior colliculus n Medial geniculate body = AUDITORY Therefore SUPERIOR COLLICULUS n LATERAL GENICULATE BODY = VISUAL

Hemianopia

blindness over half the field of vision.

What happens if damage to left optic nerve

no vision through left eye

What happens if damage to optic chiasma

= no vision of temporal visual fields

What happens if damage to right optic tract

no left eye temporal vision | no right eye nasal vision

What happens if damage to Left meyers loop (=damage to superior visual field)

no vision in superior nasal field of left eye | and superior temporal field of right eye

What happens if damage to left Baun's loop (inferior visual field)

no vision in right eye inferior temporal field | and left eye inferior nasal field

INTORTION

internal rotation towards midline

EXTORTION

External rotation away from midline

6 ocular eye muscles

Medial rectus Lateral Rectus superior oblique inferior oblique superior rectus inferior rectus

What muscles are innervated by oculomotor nerve CNIII

Medial rectus Inferior oblique superior rectus inferior rectus

Where is nucleus of oculomotor nerve located (CNIII)

periaqueductal grey near cerebral aqueduct (same as CN 4)

What is lateral rectus innervated by

Abducens CNVI

what is Superior oblique innervated by

Trochlear nerve CN IV

Where is nuclei of trochlear nerve CN IV Located

periaqueductal grey near cerebral aqueduct (same as CN4)

draw eye ,movement diagram

SR n SO intort

Where to move eye when testing Superior rectus

look laterally n upwards

Where to move eye when testing inferior rectus

look laterally and downwards

Where to move eye when testing lateral rectus

look laterally

Where to move eye when testing medial rectus

look medially

Where to move eye when testing inferior oblique

look medially and upwards

Where to move eye when testing superior oblique

look medially and downwards

LR6SO4

Lateral rectus = cn6 superior oblique = cn4 everything else = cn3