Opthalmology - Eye Anatomy Flashcards
Contents of the orbit.
- the eye
- extraocular muscles
- cranial nerve II-VI
- arterial supply and venous drainage
Layers of the eye.
Fibrous layer of the eye.
Cornea - located in the centre of the anterior aspect of the eye, and is transparent.
Sclera - covers the rest of the eye (white).
Vascular layer of the eye - contents.
- ciliary body
- choroid
- iris
Function of the ciliary body.
Attached to the lens via the suspensory ligaments, controlling the shape of the lens.
Forms the aqueous humour.
Function of the choroid.
Layer of connective tissue containing blood supply to the retina.
Function of the iris.
Structure containing the pupil, which contains smooth muscle to control its diameter.
Pupillary light reflex.
Accommodation reflex.
Inner layer of the eye.
Neural layer - composed of photoreceptors.
Pigmented layer - supports the neural layer and is continuous throughout the eye.
Photoreceptor concentration at the
a) fovea
b) optic disc
a) highest concentration
b) no photoreceptors
Sections of the eye.
Anterior and posterior chambers - aqueous humour.
Vitreous body - vitreous humour.
Extraocular muscles of the eye - innervation.
CNIII: superior rectus; medial rectus; inferior rectus; inferior oblique
CN IV: superior oblique
CN VI: lateral rectus
CN VI palsy.
CN IV palsy.
Lateral and inferior rectus muscles can compensate, meaning there is often no obvious eye displacement.
The patient may complain of diplopia, and develop a head tilt.
CN III palsy.
Depressed and abducted eyeball.
Arterial supply to the eye.
a) retina
b) choroid
c) lacrimal gland
a) central retinal artery
b) ciliary arteries
c) lacrimal artery
Venous drainage of the eye.
Central retinal and vortex veins - drain into opthalmic vein.
Pathways into the orbit.
- optic canal
- superior orbital fissure
- inferior orbital fissure
Function of the optic canal.
Transmits the opthalmic artery and optic nerve.
Function of the superior orbital fissure.
Transmits the common tendinous ring, containing:
- oculomotor nerve
- abducens nerve
- nasociliary nerve
Transmits outside the common tendinous ring:
- superior opthalmic vein
- trochlear nerve
- CN V1
- lacrimal nerve
- frontal nerve
Function of the inferior orbital fissure.
Transmits the inferior opthalmic vein and zygomatic nerve.
What is the visual field?
The entire area that can be seen by a patient without movement of their head, and with their eyes fixed on one point.
How is the image of an object in the visual field translated onto the retina?
- inverted upside-down
- flipped left-to-right
How does the retina transmit signals to the optic nerve?
Photoreceptors are stimulated by photos of light entering the eye, transmitting action potentials along the optic nerve.
What occurs at the optic chiasm?
a) nasal retinal fibres
b) temporal retinal fibres
a) nasal fibres decussate to the contralateral optic tract.
b) temporal fibres remain on their respective sides.
Optic tracts are formed.
What occurs at the lateral geniculate nucleus?
Optic tract splits into:
- superior optic radiation (lower retinal field)
- inferior optic radiation (upper retinal field)
What structure do the
a) superior optic radiations
b) inferior optic radiations
travel via?
a) parietal lobe
b) temporal lobe (Meyer’s loop)
What is the function of the calcarine sulcus?
Optic radiations terminate here, in the primary visual cortex.
This is where images from both eyes are collated and the final image is formed.
NB: the brain has to re-invert the image to the information is correctly orientated.