Ophthalmology Flashcards
Eye closure is made possible by the _____ ___ muscle, innervate by which cranial nerve?
Eye closure is done by contraction of the orbicularis oculi muscle, which is innervated by CN VII (facial nerve)
Eye opening is made possible by the _____ ___ ____ muscle, innervate by which cranial nerve?
Levator palpebrae superioris
Innervated by CN III (oculomotor nerve)
How would a palsy of CN VII affect someone’s eye?
A CN VII palsy will cause ectropion of the lower lid but NOT ptosis (as LPS is supplied by CN III)
What is the name of the border at which the cornea and slcera merge?
The limbus
The cornea is made up of three layers, what are they and which accounts for most of the thickness?
What cranial nerve innervates the cornea?
Outer epithelium
Avascular, hypocellular stromal layer (accounts for 90% of corneal thickness)
Non-replicating endothelial monolayer
The cornea is innervated by CN V1 (ophthalmic branch of the trigeminal nerve)
Tears are made up of an oily layer and an aqueous layer - what gland(s) secrete these?
Describe the path of tear drainage
Oily layer - secreted by Meibomian glands
Aqueous layer secreted by lacrimal and conjunctival glands
Tears pass across they eye, drain into the puncta (either superior or inferior), then into the canaliculi, then into the lacrimal sac, and finally into the nose via the nasolacrimal duct which passes into the inferior meatus
What nerve innervates the lacrimal gland (the primary producer of the aqueous layer of tear film), and is therefore responsible for tear production?
CN VII supplies the lacrimal gland (parasympathetic innervation)
Sympathetic innervation via CN __ causes pupillary ____
Parasympathetic innervation via CN __ causes pupillary ____
Sympathetic innervation via the long ciliary nerves given off from the optic nerve causing contraction of the radial smooth muscles to cause pupillary dilatation
Parasympathetic innervation via CN III causes pupillary constriction
What is the name of the layer of the eye that provides nutrients and oxygen to the outer layers of the retina? What layers is it sandwiched between?
The choroid
Sandwiched between the retina and the sclera
What is the name of the structure in the eye that allows for accommodation?
What else does this structure do?
The ciliary body
The ciliary body also produces aqueous humour
Generally, what is the pathophysiological mechanism behind presbyopia?
Failure of the eye to accommodate due to loss of capsule elasticity and lens deformability
The vitreous in the eye is 99% water but also contains collagen fibrils and hyaluronan. What process occurs to the vitreous as we age?
What can this result in?
The vitreous undergoes progressive liquefaction as we age
As the vitreous is particularly adherent to the retina at the optic disc, liquefaction of the vitreous can cause it to pull on the retina (causing flashing lights) and ultimately may lead to retinal detachment
Rod/Cone photoreceptors are concentrated at the macula
What function do they perform?
Cone photoreceptors are concentrated at the macula, and allow for higher visual acuity and colour vision
(Rods deal with black and white vision)
Painful sudden loss of vision - differentials
Angle closure glaucoma
Uveitis
Corneal ulcer/keratitis
Endophthalmitis
Retrobulbar optic neuritis
Orbital cellulitis
Giant cell arteritis
Painless sudden loss of vision (fleeting) - differentials
Embolic retinal artery occlusion
Migraine
Raised ICP
Prodromal symptom in Giant Cell arteritis
