Eye and Vision Physiology Flashcards
What are the three coats of the eye, from superficial to deep?
The fibrous coat, vascular coat and the sensory coat
What are the component parts of the fibrous coat of the eye?
The cornea and the sclera
What are the component parts of the vascular coat of the eye?
The iris, ciliary body and the choroid
What are the component parts of the sensory coat of the eye?
The retina
Which coats of the eye are complete and incomplete?
Complete- fibrous
Incomplete- vascular and sensory
What structure does the anterior segment of the eye lie anterior to, and what is it filled with?
The lens
Filled with aqueous humor
What structure does the posterior segment of the eye lie posterior to, and what is it filled with?
The lens
Filled with vitreous humor
In what segment of the eye are the anterior and posterior chambers found, and what structure divides them?
Both found in anterior segment
Divided by iris
Describe the drainage of the aqueous humor
The aqueous humor first drains to the trabecular meshwork in the angle of the anterior chamber, which drains to Schlemm’s canal, which drains to veins
Name the quadrants of the eye
The upper nasal, lower nasal, upper temporal and lower temporal quadrants
What kind of epithelium is present in the cornea?
Stratified, squamous, non-keratinised epithelium
What is the basement membrane of the corneal epithelium called?
Bowman’s membrane
How is transparency of the cornea maintained, histologically?
Regular arrangement of collagen
No blood vessels
Endothelial layer has a pump that keeps the aqueous humor out
What is the site of most visual acuity in the eye called?
The fovea centralis
What are the functions of the tear film?
Keeps cornea moist
Prevents drying
Washes away any particulate foreign bodies
Has antibodies and lysozymes to kill microbes
Smooths outer surface of cornea providing smooth surface for refraction.
What nerve controls secretion of tears into the conjuctival sac?
Parasympathetic fibres of the facial nerve
What structures of the eye are responsible for refraction of light?
The cornea, aqueous humor and the lens
What is the visual field?
Everything that you can see with one eye (including periphery)
Where do the nasal fibres of the optic nerve cross over?
At the optic chiasma
Which fibres of the optic nerve cross over at the optic chiasma?
The nasal fibres
Where do fibres from the optic tract synapse?
The lateral geniculate body of the thalamus
Which half of the visual cortex sees which half of the visual field?
The right half of the visual cortex sees the left half of the visual field and vice versa
What damage would be expected if one of the optic nerves is damaged?
Blindness in the ipsilateral eye
What damage would be expected if the optic chiasma is disrupted in the middle?
Bitemporal hemianopia
What damage would be expected if one of the optic tracts is damaged?
Contralateral homonymous hemianopia
What damage would be expected if optic radiation is damaged?
Contralateral homonymous hemianopia
What is the action of the intrinsic muscles of the eye as a group?
Control pupil diameter and alter lens curvature
What is the action of the extrinsic muscles of the eye as a group?
Movement of the eye
What are the names of the six extrinsic occular muscles?
Superior rectus Inferior rectus Lateral rectus Medial rectus Superior oblique Inferior oblique
Describe the innervation of the extrinsic muscles of the eye
Superior oblique- trochlear nerve
Lateral rectus- abducent nerve
All others- occulomotor nerve
What are the names of the intrinsic muscles of the eye?
Ciliaris
Constrictor pupillae
Dilator pupillae
Describe the transduction mechanism involved in vision
Trans-retinol is converted into cis-retinol in the retinal pigment epithelium, using up some vitamin A. Cis-retinol is then transported back to the rods and cones to form opsin. The cascade of reactions within the rods/cones causes a hyperpolarisation, which transmits an impulse and becomes an action potential in the optic nerve cell
What is the conjuctiva?
A thin, vascular membrane that covers the inner surface of the eyelids and the sclera
What is the cornea?
It is the anterior 1/6th of the fibrous coat of the eyeball, it is transparent and allows light rays to enter the eyeball
What is the sclera?
The posterior 5/6s of fibrous coat, opaque and gives attachments to muscles but does not move the eye
What is the function of the ciliary body?
Suspends the lens and produces aqueous humor
What is the function of the choroid?
Supplies blood to out layers of retina
What is the function of the iris?
Controls the diameter of the pupil
Is the crystalline lens biconvex or biconcave?
Biconvex
How is the crystalline lens connected to the ciliary body?
Through suspensory ligaments
What is the function of the aqueous and vitreous humors?
Aqueous- helps maintain intraocular pressure
Vitreous- Cushions the retina
How is the lacrimal gland innervated?
It receives parasympathetic innervation from the facial nerve
Where do the lacrimal ducts open into?
The conjuctival sac
How do tears drain from the eyes?
Through punctae on the medial sides of the eyelids, draining into the lacrimal sac, which drains to the nasolacrimal duct, which drains into the inferior meatus
Describe the innervation of the intrinsic muslces of the eye
Ciliaris and constrictor pupillae- parasympathetic from third nerve
Dilator pupillae- sympathetic from plexus around blood vessels
What artery supplies all the structures within the orbit?
The ophthalmic artery
What veins drain the eye, and what do they drain into?
The superior and inferior ophthalmic veins, which drain into the cavernous sinus
