Eyes Flashcards
What bones form the orbit?
Make up outer orbit:
-frontal
-maxilla
-zygomatic
Make up “bowl” of the orbit:
-sphenoid
-lacrimal (provides opening for lacrimal tear duct system)
-ethmoid
-palatine
What are the openings of the orbit?
-superior orbital fissure: long narrow opening (CN 3,4,6 and V1 of CN5 pass through here, V1 will travel up orbit to exit through supraorbital foramen)
-optic canal: circular opening (CN 2 optic nerve travels through to plug into retina)
-inferior orbital fissure: does not directly open into the internal skull (V2 of CN5 passes through here and runs along the orbit to exit through the infraorbital foramen)
What structures make up the surface anatomy of the eye?
-eyelids
-pupils and eyelids: upper eyelid usually covers upper portion of iris
-sclera: white part
-cornea: clear area in front of pupil and iris, light enters here
-conjunctiva: transparent layer over the eyeball/eyelids
-medial canthus/angles: corner of eye closest to nose
-lateral canthus/angles: corner of eye closest to ears
-palpebral fissure: distance between two eyelids
What are the layers of the conjunctiva and what is its main purpose?
-palpebral conjunctiva: on top of the eyelid
-bulbar conjunctiva: on top of the eyeball
-inferior conjunctival sac: space in the bottom eyelid between junction of eye and eyelid
-purpose: protection from external environment
What is conjunctivitis? What about subconjunctival hemorrhage?
Conjunctivitis: canjunctiva of eye is inflamed (pink eye), can be caused by bacteria or virus
Subconjunctival hemorrhage: blood accumulates behind conjunctiva (self limiting/short lasting and relatively harmless), can be caused by any minor trauma causing a rupture
What glands are located in the eyelids?
Meibomian gland (tarsal gland): sebaceous glands at the end of each eyelid that secrete lipid fluid to lubricate the conjunctival surfaces (to help with movement
-works synergistically with tears and lacrimal system
What are the muscles of the eyelids?
-levator palpebral superioris: extraoccular muscle inside the orbit/above eyeball which elevates and retracts the eyelid (CN3 innervation)
-superior tarsal muscle: smooth muscle located in the eyelid which assists with raising the eyelid (sympathetic innervation)
***ptosis: when the eyelid droops over the eye due to damage to the muscles or nerves (sympathetic/CN3)
What are the lacrimal structures of the eye?
-lacrimal gland: located in superior lateral orbit above eyeball tears are secreted onto the eyeball
-lacrimal lake: region of medial eyeball where tears are secreted and gather
-lacrimal punctum: openings in the eyelid which allow for tears to drain out of the eye into the canaliculi
-lacrimal canaliculi: canal/pathway for tears to exit the eye area
-lacrimal sac: large cavity which collects tears from the canaliculi
-nasolacrimal duct: drains tears into the inferior nasal meatus (just under the lowest/largest turbinate)
***lacrimal structures produce tears which flow into the nasal cavity from the eye
What are the three layers of the eyeball?
-outer (fibrous) layer
-middle (vascular) layer
-inner layer (retina)
What forms the outer layer of the eyeball?
-sclera (white of the eye, attachment site for extraoccular muscles)
-cornea (transparent portion in front of pupil/iris)
What is the corneal reflex for a neuro exam?
The cornea is one of the most sensitive tissues in the body to touch (innervated by V1 of CN5)
Patient will blink in response to touch
***usually only done for comprehensive neuro exams during comatose or to determine death
What makes up the vascular layer of the eyball?
-choroid: dense vascular bed in eye (red eye reflection in photos)
-iris: contracts anterior surface of lens, controls light entering eye
-ciliary body: junction between choroid and iris
>muscular section: suspensory ligaments attach to the muscle which support the lens allowing accommodation/thickening of the lens for focusing
>vascular section: blood vessels which produce aqueous humor which is secreted into the posterior chamber and flows to the anterior chamber (drains into scleral veins/venous sinus)
*production must match drainage in order to maintain normal pressure of the eye
What is a suprachoroidal hemorrhage?
A rare condition which can be caused by trauma/complications in ocular surgery
During a suprachoroidal hemorrhage, short or long ciliary arteries which supply the choroid layer will rupture and blood will accumulate behind the retina (pushing the retina up and out)
**serious threat to vision if blood is not reabsorbed or surgically removed: blindness
What structures form the inner layer of the eye?
-Retina
>optic disk: where CN2, sensory axons, and blood vessels enter the eye (no photoreceptors here: blind spot) located in medial part of eye
> optic cup: pit in the center of optic disk with no nerve fibers (where retinal arteries are entering the eyeball itself)
> macula: region of visual acuity or functional center of retina more lateral than the optic disk
> fovea centralis: area with greatest amount of photoreceptors, greatest visual acuity (middle of macula)
What is the proper cup to disc layer in the eyeball? What happens if there is a variation in this ratio?
Normal: 1:3 (optic cup should be 1/3 of the total width of the optic disk)
If greater than 1/3 of the width: begin suspecting/ruling out pathology (not diagnostic but needs to be investigated), could signify something like glaucoma
***some patients may have a variation with no issues present (normal variations), yet this is relatively rare, usually variations will be a concern
