2.2.1 Eye and Orbit Flashcards
What is the Iris of the eye?
Iris: pigmented diaphragm which surrounds the pupil
What are the covered parts?
What is presbyopia?
lens elasticity lost with age, causing difficulty with near sight
Draw the H test with nerves and muscles.
What is ptosis?
failure of superior tarsal muscle (Muller’s m)
What is the orbital septum?
-connective tissue extending beyond borders of tarsal plate to margin of orbit
What is the anterior chamber of the eye?
- 1) Anterior Chamber: anterior to the iris and the pupil
- Filled with aqueous humor, which drains into the canal of Schlemm
What is the palpebral conjunctiva?
bulbar conjunctiva that has reflexed off of the sclera and onto the inner surface of the eyelids
What is the superior orbital fissure and what does it allow passage of?
-Superior Orbital Fissure: between lesser and greater wings of sphenoid; passage for what 5 things?
- CN III
- CN IV
- CN V 1 (ophthalmic division)
- CN VI
- Superior Ophthalmic Vein
What eye muscle is innervated by CN VI?
lateral rectus
Most of the orbital structures receive blood from what artery?
Ophthalmic
What are the important veins of the orbit?
- Orbital structures are drained by two major veins:
- 1) Superior ophthalmic vein
- 2) Inferior ophthalmic vein
- Both of these veins anastomose with veins leading into the facial vein and into the cavernous sinus and/or pterygoid plexus
- Both veins pass through the superior orbital fissure or fuse to form a single superior ophthalmic vein
What is the most common cause of a lesion of CN III?
-Most common cause of sudden CN III palsy is an aneurysm within the posterior communicating artery of the brain
What are the two glands associated with eyelashes?
- Sebaceous glands of Zeis
- Apocrine sweat glands of Moll
What are the covered parts?
What is the common cause of a CN VI palsy?
- Most commonly caused by DM or conditions which increase intracranial pressure, stretching CN VI due to brain being pushed into ]foramen magnum
- CN VI palsy is the most common CN palsy
What are the characteristics of the lens of the eye? How does the lens function when looking at objects in the distance vs close up?
- Lies in the posterior chamber and is connected to the ciliary body through a series of connective tissue strands called suspensory ligaments of the lens
- When gazing at objects in the distance, the lens is held flattened by tension of the zonular fibers and normal intraocular pressure
- When accomodating to look at closer objects, the ciliary muscles within the ciliary body contract, releasing the tension on the zonular fibers and allowing the inherent elasticity of the lens to round up and refract more light
-Ciliary Muscle
-Smooth muscle, innervated by parasympathetics from CN III
-Responsible for accommodation for near sight
What is are the signs of an Abducens (CN VI) nerve lesion?
-Weakness or paralysis of the lateral rectus muscle causing the affected eye to rotate inward and medially due to unopposed action of medial rectus muscle
What is the role and innervation of the lavator palpebrae superioris?
- Main elevator of the upper eyelid
- Skeletal muscle under voluntary control
- Innervated by CN III
The optical canal transmits what two things?
-Optic Canal: transmits CNII and the ophthalmic artery
What happens to the fundus during hypertension?
- Hypertension: causes the arteries to become swollen and restrict venous return
- Will be visible as venous nicking
What is the sclera of the eye?
Sclera: white of the eye; dense connective tissue continuous with the dura mater of the optic nerve and brain
What is the purpose of blinking?
-Each blink of the eyelids helps to sweep tears into the lacrimal puncta
What is the action of the superior oblique vs inferior oblique eye muscle?
Superior oblique - rotates the top of the eye toward nose
Inferior - rotates top of eye away from nose
What are the covered parts?
What is the cornea?
Cornea: clear extension of the sclera, covering both the iris and the pupil
What is the role of the superior tarsal muscle and what is the innervation? What can be a result of loss of this innervation?
- Aids in elevation of the upper eyelid
- Smooth muscle innervated by sympathetic fibers
- Ptosis: drooping of eyelid due to loss of sympathetic innervation
What is the role and innervation of the orbicularis oculi?
Orbicularis Oculi:
- Innervated by temporal and zygomatic branches of CN VII
- Palpebral portion: normal eyelid closure
- Orbital portion: forced eyelid closure
What is the posterior chamber of the eye?
- 2) Posterior Chamber: posterior to iris and pupil but anterior to lens and ciliary process
- Ciliary process produces the aqueous humor which enters the anterior chamber
What is the blow out fracture?
-Typically, a blow-out orbital fracture involves breakage of the maxillary bone with subsequent protrusion of orbital contents into the maxillary sinus
What is the role of the dilator and sphinctor muscles in the iris?
-1) Dilator Muscle
- -Myoepithelial cells innervated by postganglionic sympathetic from superior cervical ganlgia
- -Receptors respond to NE from sympathetic nerves
- -Opioids will cause miosis of the pupil (constriction)
-2) Sphincter Muscle
- -Smooth muscle innervated by postganglionic parasympathetic fibers from the ciliary glanglia via short ciliary nerves (from CN III)
- -Receptors respond to ACh
- -Atropine will cause mydriasis of the pupil (dilation)
What are the covered parts?
Are the characteristics of conjunctivitis?
- Inflammation of the conjunctiva commonly caused by an allergic reaction or infection
- Allergic: itchy
- Viral: associated with a cold and watery discharge
- Bacterial: mucopurulent discharge
What is the bulbar conjunctiva?
Bulbar Conjunctiva: thin, moist mucous membrane covering the sclera
What is strabismus, esotropia and exotropia?
What is exophtalmos?
What are the covered parts?
What is the pupil of the eye?
Pupil: dark, circular aperture which allows light into the eye
What is the pathway that tears will take?
- Tears produced in the lacrimal gland flow out of lacrimal ducts across the conjunctiva
- Tears will accumulate at the lacrimal lake atop of the lacrimal caruncle and into the lacrimal puncta
- From the puncta, tears flow through the lacrimal canilicula into the lacrimal sac and down nasolacrimal duct into the inferior meatus (under inferior nasal turbinate)
Blood supply to the neural retina comes from?
Central retinal artery
What eye muscle is innervated by CN IV?
-superior oblique
What is the role of the oblique eye muscles?
- Superior oblique muscle runs through a pulley (trochlea) at the sup/med margin of the frontal bone, then inserts into the sclera of the eye
- Inferior oblique muscle arises from the maxillary bone margin lateral to the nasolacrimal duct and inserts into the sclera of the eye in the inf surface in the post lateral quadrant
- Tend to protrude eyes within the orbit
What eye muscles are innervated by CNIII?
-medial rectus, superior rectus, inferior rectus, inferior oblique
What are the signs of a trochlear nerve (CN IV) lesion?
- Affected eye will be tilted outward due to superior oblique paralysis
- Head will tilt to unaffected side to correct for this movement
What are the characteristics of a sty (Horedolum)?
- Acute purulent inflammation of the eyelid
- Generally caused by staph aureus bacteria
- Internal sty represents inflammation of a meibomian gland just under conjunctival side of the eyelid
- External sty arises from an eyelash follicle or lid-margin glands
What is the orbit and what makes up the orbital margin?
- Bony pyramidal sockets in which eyes and associated structures reside
- Orbital margin is formed in thirds by the frontal, zygomatic, and maxillary bones
- Orbit is lined by periosteum (periorbita)
What is the role of the tarsal plate?
-dense connective tissue that gives form to each eyelid
What is the pathway of the corneal reflex?
V1 test, causes blinking when outside the visual field
What is the Sclerocorneal Junction (Limbus)?
anterior extension of the cornea where the iris meets the sclera
What are the covered parts?
What are the characteristics of an oculomotor (CN III) Nerve lesion?
- Lateral Strabismus: eye rotates down and abducted due to unopposed action of lateral rectus ands superior oblique muscles
- Will cause diploplia
- Ptosis: due to paralysis of levator palpebrae
- Mydriasis: dilation of pupil
- Loss of accommodation
What are the covered part? (It was mentioned you should be able to draw this)
What are the 3 layers of the eye?
-1) Sclera: outer, dense connective tissue layer
- Site of insertion for the oculomotor muscles
- Continuous with the cornea
- 2) Choroid: middle, vascular layer
- Consists of the ciliary body and iris
- 3) Retina: inner layer
- Divided into neural retina and pigmented retina
What is the importance of the tarsal (Meibomian) glands?
-embedded within the plates, secreting fatty lubricants to prevent eyelids from sticking to each other and produce a lipid layer to float atop aqueous tear layer
What are the covered parts?
What is papilledema?
- Papilledema: optic disc swelling caused by an excessive CSF pressure
- Venous blood will pool in the veins on the surface of the retina
What are the characteristics of glaucoma?
- Excessive pressure within the eye affecting 2% of people over 40 and 10% over 80
- Second leading cause of blindness in the world
- Two classifications
- Open Angle
- Closed Angle: caused by blockage of fluid draining from Canal of Schlemm
- Untreated, causes increased pressure leading to inadequate blood flow to the retina, causing slow onset blindness
- Eye pressure can be checked by blowing air onto the surface of the eye and measuring the deformity of the cornea
- Optic disc atrophy with progressive peripheral visual field loss if untreated.
Draw a diagram of a transverse section through the optic nerve.
What is the use of gold in the upper eyelids?
What are the characteristics of a Chalazion?
- Lump in the eyelid as a result of the chronic blockage of one of the tarsal glands
- Normally is not infected and not painful
Draw a diagram depicting the change in the Lens ciliary muscle in distance vison and near vison.
What is the lacrimal gland and what is the innervation?
- Lacrimal Gland: almond-sized gland in ant/sup lateral portion of orbit; produces 1ml tears per day, which moisten the cornea through 3-12 excretory ducts
- Secretions form the lacrimal gland are controlled by parasympathetic nerve originating in CN VII and synapsing on pterygopalatine ganglion
