Vision Flashcards
What bones make up the bony orbit?
maxilla, zygomatic, frontal, ethmoid, lacrimal, sphenoid and palatine bones
What bones make up the roof of the bony orbit?
orbital part of the frontal bone.
What bones make up the medial wall of the bony orbit?
maxilla, lacrimal, ethmoid and sphenoid bones.
What bones make up the floor of the bony orbit?
orbital part of the maxilla (small contributions from the zygomatic and palatine bones)
What bones make up the lateral wall of the bony orbit?
zygomatic bone anteriorly and greater wing of the sphenoid posteriorly
Label bones of the bony orbit (diagram).
What kind of tears can the lacrimal system produce?
Basal tears: constant fluid secretion by the lacrimal gland
Reflex tears: response to irritation (afferent V1, efferent PSNS)
Emotional tears
Explain the normal movement of basal tears.
move across the eyeball as the eyelids blink, accumulating medially in the lacrimal lake
Label diagram of eye.
Where are the lateral and medial Canthi located? Where is the caruncle located?
Canthi: the corners of the eye.
Caruncle present in medial canthus.
What are the Puncta?
medial openings that drain fluid into the lacrimal canaliculi to the tear sac
What is the role of the tear duct/sac?
fluid accumulates in the sac before draining to the nose via the tear duct
What the three layers of tear film?
Superficial oily layer: reduces evaporation (produce by glands in eyelid)
Aqueous tear film: produced by lacrimal gland
Mucinous layer: on corneal surface - maintains surface wetting (produced by conjunctival goblet cells)
What are the functions of tear film?
Maintain smooth cornea-air surface
Supplies oxygen to cornea (not normally vascularised)
Removes debris
Bactericidal
What is the conjunctiva?
thin, transparent tissue that covers the eye, beginning at the other edge of the cornea to cover visible eye and inside eyelids - nourished by tiny blood vessels
Diagram of cross section of the eye
What are the components of the outside coating of the eye (3 layers).
Sclera: hard and opaque
Choroid: pigmented and vascular
Retina: neurosensory tissue
What is the role of the sclera?
Protect the eye. Tough and opaque. High water content.
Explain the role of the cornea.
transparent, dome-shaped window in front of eye, providing 2/3 eye’s focusing power; continuous with scleral layer and physical/infection barrier. Low water content.
What are the 5 layers of the cornea?
Epithelium
Bowman’s membrane (basal membrane for the epithelium)
Stroma (nerve endings for sensation/nutrition)
Descemet’s membrane (basal membrane for the endothelium)
Endothelium (removes fluid and prevents corneal oedema)
Cross sectional diagram of eye.
What is the uvea? Where is it found? What is it composed of?
vascular coat of the eyeball, lying between sclera and retina - composed of iris, ciliary body and choroid
What is the choroid? Give its composition and function.
lies between retina and sclera - comprised of blood vessels that nourish eye
What is the iris? What is its function?
coloured part of the eye, controlling diameter of pupil using pupil constrictor/dilator muscles to adjust light levels
what are lens zonules?
fibrous rings that suspend the lens in the eye
What is the function of the lens?
1/3 refractive power of the eyes and accommodation for near vision
Explain the structure of the lens.
outer acellular capsule. Regular inner elongated cell fibres (regularity = transparency).
Contains collagen fibres
What is the retina and its function?
Thin layer of tissue lining inner eye. Captures light entering eye.
What is the role of the optic nerve? where is it located?
trasmit impulses fdrom retina –> brain. Connected at the back of the eye near the macula.
Where is the macula located? What is its role?
located centrally, anterior to the optic nerve. Small + highly sensitive region for detailed central vision.
Where is the fovea located?
pit at centre of the macula.
Diagram showing the anterior vs posterior segment of the eye.
What is the boundary of the posterior/anterior segments?
the lens
Where is the anterior chamber found? What is it filled with?
Berween lens and cornea.
Clear aqeous fluid which supplies nutrients.
Where is the posterior chamber found?
between lens zonules and the back of the iris.
What segment are the anterior and posterior chambers found in?
anterior chamber.
what segment is the vitreous chamber found in?
posterior segment.
Where is the vitreous chamber found?
between the lens and retina
What is the role of the ciliary body?
secrete AqH to eye to supply nutrients.
How does AqH flow?
anteriorly to anterior chamber. Drained by trabecular network.
How is AqH drained?
80-90% –> trabecular network (Canal of Schlemm).
Rest via uveal-scleral outflow (passive reabsorption).