What are the 3 layers of the eyeball?
Fibrous
Vascular
Sensory
What does the fibrous layer consist of?
Cornea
Sclera
What does the vascular layer consist of?
Choroid
Ciliary body
Iris
What is the function of the cornea?
Provides shape to the eye and supports deeper structures.
Transparent - light entering through it is refracted.
What is the function of the sclera?
Provides attachment for the extraocular muscles of the eye that control its movement.
White part of the eye.
What is the function of the choroid?
Layer of connective tissue and blood vessels that supplies the outer layers of the retina with nutrients.
What is the function of the ciliary body?
Suspends and controls the lens shape (accommodation) and produces aqueous humour.
What is the function of the iris?
Contains smooth muscle fibres that control the diameter of the pupil. Innervated by the autonomic nervous system.
What is the function of the retina?
Detects light
What is the macula?
The centre of the retina. It is highly pigmented and has many light detecting cells.
Contains a depression called the Fovea - highest vision acuity.
What is cataract?
When the lens becomes opaque. Normally due to old age.
What is the anterior chamber?
Everything in front of the iris.
What is the posterior chamber?
Everything behind the iris.
What is the function of aqueous and vitreous humour?
Maintains the pressure of the eyeball. 21mmhg.
What are the 3 openings at the apex of the eye?
Optic foramen
Superior Orbital fissure
Inferior Orbital fissure.
What is the conjunctiva?
Mucous membrane that covers the front of eye and lines the insides of the eyelids.
Keeps the eyes moist so they can open and close easily - contains goblets cells within its epithelium.
What is the function of the lacrimal gland?
Serous exocrine glands
Located in orbital fossa.
Secretes tears which act to lubricate and protect the cornea.
What is the route of tears?
lacrimal gland - lacrimal duct - punctae - cannaliculi - lacrimal sac- Nasolacrimal duct - inferior meatus.
What is the function of extraocular muscles?
Control the movement of the eyeball.
What is the function of intraocular muscles?
Control pupil diameter.
Alter lens curvature
What are the 6 extrinsic muscles?
Superior rectus Medial rectus Inferior rectus Lateral rectus Superior oblique Inferior oblique.
What is the innervation of the extrinsic muscles of the eyeball?
Superior oblique - CN IV trochlear
Lateral Rectus - CN VI abducent
Everything else - CN III oculomotor.
What muscle is responsible for elevating the upper eyelid?
Levator Palpebrae Superioris.
What is the action of the medial rectus?
Adduction
What is the action of the lateral rectus?
Abduction
What is the action of the superior rectus?
Elevation, Adduction, Intorsion.
What is the action of the inferior rectus?
Depression, Adduction, Extorsion
What is the action of the superior oblique?
Intorsion, Depression, Abduction
What is the action of the inferior oblique?
Extorsion, Elevation, Abduction.
What makes up the left visual field?
Left nasal and right temporal fibres.
What makes up the right visual field?
Right nasal and left temporal fibres.
What are the steps of the visual pathway?
1 - Optic nerve leaves eye
2- Optic nerves join at optic chiasma.
3- Nasal fibres cross over to contralateral side
4- Optic tracts split from chiasma
5- Fibres synapse at Lateral Geniculate Body of thalamus
6- Optic radiation then travels to Primary visual cortex (area 17).
What would happen to an individuals eye sight if they suffered a right optic nerve lesion?
Patient would have blindness in right eye.
Right optic nerve carries right temporal and right nasal fibres.
What would happen to an individuals eye sight if they suffered from a pituitary adenoma compressing on their optic chiasma?
Patient would have bitemporal hemianopia.
Optic chiasm is site of nasal fibre decussation so they could no longer see temporal sides.
What would happen to an individuals eye sight if they suffered an optic tract or optic radiation lesion?
Patient would have contralateral homonymous hemianopia.
Carries fibres from both left and right sides.