the orbit and eye Flashcards
what is the white part of the eye called?
sclera
what covers the sclera?
conjunctiva
what are conjunctival vessels?
veins in the white part of the eye (sclera)
what covers the iris?
cornea
what is found between the cornea and sclera?
limbus (corneoscleral junction)
what does the conjuntiva cover?
- reflects onto the eyelid and upper eyelid (conjunctival fornix)
- covers the sclera
what is the outer layer of the eye made of?
fibrous tissue
what parts is the outer layer of the eye made up of?
2 parts
sclera- muscle attachment
cornea- 2/3 of refractive power
what is the middle layer of the eye also known as?
-uvea or vascular layer
how many parts can the uvea be broken down into and what are they?
-3 parts
iris- pupil diametes
ciliary body- controls iris, shape of lens and secretion of aqueous humour
choroid- nutrition and gas exchange (thickest part)
what is the inner layer of the eye also called?
retina (photosensitive layer)
what can the anterior segment (infront of the lens) of the eye be divided into?
- anterior chamber (between cornea and iris)
- posterior chamber (between iris and suspensory ligaments)
what does the posterior segment (behind the lens) contain?
- contains vitreous body
- vitreous humour
- vitreous body is a common location for ‘floaters’
what is a cataract?
clouding of the lens
what is the iridocorneal angle?
- the angle in ‘open-angle’ and ‘closed-angle- glaucoma
- junction or area between the iris and cornea
what is circulation of aqueous?
- liquid produced and secreted in ciliary body due to the processes
- it then passes into the posterior body, over the lens, nourishing the lens
- it then passes through the opening of the pupil into the anterior chamber, once in the anterior chamber it can circulate and nourish the internal aspect of the cornea
- the aqueous is then reabsorbed into the scleral venous sinus (canal of Schlemm) at the iridocorneal angle
what can occur if there is raised intra ocular pressure?
ischaemia and glaucoma
what supplies most of the blood to the eye?
opthalmic artery
what does the opthalmic artery derive from?
- the internal carotid artery
- passes through the cavernous sinus and branches off into the opthalmic artery
what is an end artery?
-an artery with insufficient anastamoses to maintain viability of the tissue supplies if arterial occlusion occurs
what is the only artery that supplies the retina and why is it important?
- the central artery of the retina (its an end artery)
- if it gets blocked you get ischamia of the retina
what is the only vein that drains into the retina?
the central vein
what is the danger triangle of the face?
-upper lip/external nose
what is highlighted pink?
the superior ophalmic vein
what is highlighted pink?
the optic nerve
what is highlighted pink?
-the inferior ophalmic vein (drains mainly into the superior opthalmic vein)
what does the fundus include?
- optic disc
- macula
- fovea
what is the fundus?
- the posterior area where light is focused
- it includes the optic disc, macula and fovea
what is the optic disc?
- part of the fundus
- point of CNII formation
- only point of entry/exit for blood vessels and axons of CNII
- blind spot!!
what is the macula?
-part of the fundus with the greatest density of cones
what is the area of most acute vision in the fundus?
-fovea
how is light seen in the retina?
- the photoreceptors pick up the cells
- ganglions create a synapse to carry on the pulse to the axons
- the axons of the ganglion cells send the signals to the optic nerve
why is the optic disc known as a blind spot?
-it does not have any photoreceptors
where do the retinal veins and arteries lie in relation to the retina?
-they lie anterior to the retina
what is looked at in a fundoscopy?
fundus
what is highlighted pink?
macula of retina
what is highlighted pink?
branches of retinal vessels (anterioles and venules)
what is highlighted pink?
optic disc
what is highlighted pink?
the central artery of the retina and the central vein of the retina
which part of the eye will light from the left visual field hit?
-right side of both eyes (vise versa with right)
where does the light from the left visual field get processed in the brain after getting transferred at the optic chiasm?
right hand side of the brain
does the superior oblique muscle pas through the trochlear?
yes it does
when we are describing the movement of the eyeball what are we actually describing the movement of?
-where the pupil has moved from the primary position (looking forward)
what does movement around the vertical axis allow?
-adduction of abduction of the pupil
what does movement around the transverse axis allow?
-elevation or depression
what does movement around the A-P axis allow?
- medial or lateral movement of the superior pole of the eyeball
- medially AKA intorsion
- lateral AKA extorsion
what is also tested when you are testing the individual extraocular muscles?
their nerve supply
what is the role of the superior rectus?
- extraocular muscle
- elevation of pupil only (when eye is in abduction)
-it attaches slightly medially to the line of vision, pulling the eyeball down when contracting and elevating the pupil, due to being slight on medial line if the eye is not already in abduction the superior rectus will cause abduction so to test the superior rectus the eye must be already abducted
what is the role of the inferior rectus?
- extraocular muscle
- depression of pupil only (when abducted)
what is the role of the lateral rectus?
-only abducts eyeball
how would you test the lateral rectus in the right eye?
-ask patient to look towards right and lateral rectus would cause abduction
what enrve innervates the lateral rectus?
CN VI (abducent)
what extraocular muscles in the eye are brought into line with when abducting?
-superior and inferior rectus
what nerve innervates the superior rectus?
CN III (oculomotor)
what is the only thing the medial rectus can do?
- adduct the eyeball
- brings the line of gaze into the same plane as superior oblique and inferior oblique attachments
what innervates the medial rectus?
CN III (oculomotor)
what should be done if you want to test inferior oblique?
-put eye into adduction
role of inferior oblique?
elevates pupil
what nerve innervates the inferior oblique?
Oculomotor CNIII
what is the role of the superior oblique?
-depression of eyeball
what nerve innervates the superior oblique?
CN IV (trochlear)
what muscles allow pure elevation and how?
- superior rectus and inferior oblique muscles
- work together to elevate
- cancel each other out as superior rectus wants to rotate medially whereas inferior oblique wants to pull laterally
how does pure depression occur?
- inferior rectus and superior oblique work together to depress the eye
- cancel eachother out as inferior rectus wants to abduct and superior oblique wants to adduct
how many bones is the orbit made up of and what are they?
7 bones
- palatine bone
- sphenoid
- ethnoid
- lacrimal
- frontal
- zygomatic
- maxilla
(nasal shown in picture but not part of orbit)
Name the 7 bones of the orbit and say which is which on the diagram
- palatine (not pictured)
- sphenoid (red)
- ethmoid (yellow)
- lacrimal (dark blue)
- maxilla (purple)
- frontal (sand)
- zygomatic (light blue)
how many orbital plates are there in the orbit and what are their names?
3
- orbital plate of frontal
- orbital plate of ethmoid
- orbital plate of maxilla
(orbital plate is a flat plate on the bone)
what orbital plates in the orbit are more susceptible to fractures?
-orbital plate of the maxilla and ethmoid bone as they are thinner
what is highlighted pink?
optic canal
what structures pass through the structure highlighted pink?
- optic nerve
- opthalmic artery
highlighted pink=optic canal
what is highlighted pink?
superior orbital fissure
