Term
| what covers the eyelid externally? |
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Definition
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Term
| what covers the eyelid internally? |
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Definition
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Term
| what is the palpebral conjunctivum of the eyelid continuous with? |
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Definition
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Term
| what muscle forms the muscular portion of the eyelids? |
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Definition
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Term
| which glands lubricate the edges of the eyelids to prevent them from sticking together as they close? |
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Definition
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Term
| what elicits the blink reflex? |
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Definition
Blink reflex elicited by touching cornea (wisp of cotton to gently touch cornea, touching afferent is trigeminal, efferent facial n), (anticipation of eye being touched may cause you to blink)
you blink to spread tear film from lacrimal gland, travels across cornea to drain into lacrimal duct, cornea needs to continuously be wet, if you don’t blink your cornea gets dry and will ulcerate, can go blind from ulceration |
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Term
| what is the corneal reflex? |
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Definition
Important reflex that protects the eye
Stimulus to cornea carried in afferent axons in the trigeminal nerve (CN V)
Efferent axons in the facial nerve contract orbicularis oculi muscle
Loss of reflex with facial nerve injury causes corneal damage and ulceration
Also known as the blink reflex |
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Term
| what muscle elevates the upper eyelid and what nerve innervates it? |
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Definition
Levator palpebrae superioris muscle elevates upper lid
Innervated by the oculomotor nerve (III) |
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Term
| paralysis of the muller's muscle causes what? |
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Definition
Müller’s muscle is smooth muscle
Innervated by postganglionic sympathetics from the superior cervical ganglion
Paralysis causes ptosis or drooping of the upper lid
Part of Horner’s Syndrome |
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Term
| what is the lacrimal gland responsible for and what nerve innervates it? |
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Definition
Tear production controlled by parasympathetic innervation from facial nerve (VII)
Also sympathetics
Tears contain lysozyme and IgA
Tear film continuous
Tears drain into lacrimal puncta and via caniliculi into lacrimal sac that empties via nasolacrimal duct into inferior nasal meatus |
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Term
| what bones compose the 4 walls of the orbit? |
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Definition
Four walls
Superior – orbital portion of frontal bone
Medial – mostly ethmoid bone
Inferior wall – mainly maxillary bone with contributions from zygomatic and palatine bones
Lateral wall – frontal portion of zygomatic bone and greater wing of the sphenoid bone
Apex
At the optic canal in the lesser wing of the sphenoid. |
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Term
| is the orbital bone thick or thin? |
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Definition
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Term
| how are the medial and lateral walls arranged in the orbit? |
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Definition
Medial walls are parallel, one to another
Lateral walls are approximately at right angle to one another
Orbital axes diverge at 45° |
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Term
| what happens during a blowout fracture to the orbit? |
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Definition
Thin walls allow fractures that can involve the sinuses.
Medial wall fractures can involve the ethmoid sinuses
Injury to the floor can involve the maxillary sinus
Damage to the roof can involve the frontal lobe of the brain
Bleeding into the orbit may cause eye to protrude –called exopthalmos. |
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Term
| what are the contents of the orbit? |
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Definition
Periorbita
Periosteum
Orbital fat
Padding
Allows eye movements
Nerves and vessels
Extraocular muscles
Eye (bulbus oculi)
Lacrimal apparatus |
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Term
| what muscle is attached to the floor of the orbit? |
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Definition
| the inferior oblique muscle |
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Term
| the opthalmic artery is the branch of which artery? where does it supply? |
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Definition
1st branch of internal carotid artery
Major blood supply to orbit
One of smallest branches is the central artery of the retina, occlusion of which can cause blindness in that eye
Gives off central retinal artery that enters optic nerve to get to the retina
Posterior ciliary arteries penetrate sclera to supply choroid and outer retina (pigment epithelium and rods and cones) |
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Term
| as the opthalmic artery approaches the back of the eyeball it forms which artery? |
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Definition
| the central artery, supplies inner layers of the retina |
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Term
| true or false: the smallest branch of the opththalmic artery that goes into the retina is very vulnerable |
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Definition
true
embolus from heart can lodge in the central artery and cause instant blindness |
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Term
| do any arteries anastomose with the central artery? |
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Definition
no
if its occluded you go blind |
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Term
| do the veins of the orbit have valves? |
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Definition
no, valveless
metastases can travel easily
venous plexus in region of intratemporal fossa travel back into pterygoid plexus
infections in the head are very dangerous because there are so many routes they can travel to infect the brain |
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Term
| which veins drain the orbit? |
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Definition
| venous drainage of the orbit is through the superior and inferior ophthalmic veins, which pass through the superior orbital fissure and enter the cavernous sinus |
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Term
| which muscles attach to the tendinous ring? |
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Definition
| the superior, medial, lateral and inferior rectus muscles |
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Term
| which nerves reside in the tendinous ring? |
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Definition
| optic nerve, abducent nerve, oculomotor nerve, nasociliary nerve, and ophthalmic artery (within optic nerve) reside in ring |
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Term
| what are the 4 muscles that arise from the tendinous ring responsible for? |
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Definition
Lateral rectus - abduction
Inferior rectus – downward gaze
Medial rectus - adduction
Superior rectus – upward gaze |
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Term
| which nerves lie outside the tendinous ring? which lie inside? |
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Definition
| trochlear nerve, lacrimal and frontal nerves lie outside ring, while oculomotor, abducent, nasociliary and optic nerves and ophthalmic artery lie within |
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Term
| which muscles does the oculomotor nerve (CNIII) innervate? |
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Definition
4 extrinsic eye muscles as well as the levator palpebrae superioris
Superior rectus – elevates, adducts, medially rotates eye
Medial rectus – adducts eye
Inferior rectus – depresses, adducts, laterally rotates eye
Inferior oblique – elevates, abducts, laterally rotates eye |
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Term
| which muscle does the trochlear nerve (CN IV) innervate? |
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Definition
| Superior oblique – depresses, abducts, medially rotates eye |
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Term
| abducents nerve (CN VI) innervates which muscle? |
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Definition
| Lateral rectus – abducts the eye |
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Term
| if the lateral rectus muscle contracts what does the eye do? |
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Definition
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Term
| if the medial rectus muscle contracts what does the eye do? |
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Definition
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Term
| does the superior rectus muscle attach to the eyeball along its axis? |
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Definition
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Term
| how would a physician go about testing the eye muscles individually? |
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Definition
To test the muscles individually, you must line the axis of the eyeball with the axis of muscle pull.
To do this for the superior and inferior recti, you ask the patient to look laterally, i.e. abduct the eye being tested.
To do this for the obliques, you ask the patient to adduct the eye being tested. |
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Term
| to test the superior and lateral rectus muscle, where would you have the patient look? |
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Definition
| laterally, then up for superior rectus and down for inferior rectus |
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Term
| to test the superior and inferior oblique where would you have the patient look? |
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Definition
| ask the patient to look medially and then up for inferior oblique and down for superior oblique |
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Term
| what is an abducents palsy? |
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Definition
affects lateral gaze
when staring straight ahead (primary gaze) affected eye pulled medially by unopposed medial rectus
unaffected eye is center, affected eye is more medial (lateral rectus knocked out)
when look right, left eye goes nasally, right eye more midline (other muscles involved) |
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Term
| what occurs during a trochlear palsy? |
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Definition
Hypertropia – affected eye looks upward when patient asked to stare ahead
Patient suffers from diplopia
Patient tilts head downward away from affected eye to compensate
incredible difficulty walking down stairs since one eye is laterally rotated (unopposed) while other is not
tuck chin in and tilt head away from affected side to get eyes in same place, compensatory mechanism for double vision |
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Term
| what occurs during an oculomotor palsy? |
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Definition
Affects 4 of six extraocular muscles
Affected eye stares down and out due to unopposed actions of lateral rectus and superior oblique muscles
Patient cannot elevated upper lid
Cannot stare at object as it is moved toward face (impaired adduction)
Diplopia
Pupil of affected side dilated due to unopposed action of sympathetics on dilator pupillae muscle |
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Term
| is the visual axis of the eye different from the anatomical axis? |
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Definition
yes
visual axis coming from fovea centralis (central vision) = area of most acute vision
transition from neuroretina to 2 layered retina with no receptor cells (red line)
layer outside of retina, choroid, spongy tissue with lots of melanocytes (pigmented cells) and vasculature
outermost layer of eyeball= sclera, white part of eyeball, dense connective tissue, attached are extraocular eye muscles
optic nerve is CNS structure, oligodendroglial cells that myelinate axons
coming into optic disc, blind spot, no receptor cells there, don’t know blind spot is there because each eye is looking from different perspectives
-different parts of retina being stimulated at any moment
optic n innerv innermost layers of retina
aqeuous humor and sclera keep eye intact, lens in position |
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Term
| the optic vesicles form as evaginations of the developing _______. |
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Definition
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Term
| during eye development, the hyaloid artery becomes which artery? |
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Definition
| the central artery of the retina |
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Term
| during eye development, the developing lens induces the overlying ectoderm to form which epithelium? |
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Definition
the corneal epithelium
the rest of the cornea is mesodermal in origin |
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Term
| what are the 3 layers/coats of the eye? |
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Definition
outermost layer is the fibrous coat
sclera - very dense connective tissue. White portion of eye. Composed of bundles of collagen fibers running parallel to the surface of the eye.
cornea – anterior, transparent and avascular
middle layer is the vascular coat or uveal tract
consists of the choroid, the ciliary body and the iris
Innermost layer is the retina |
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Term
| describe the sclera of the eye |
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Definition
| very dense connective tissue. White portion of eye. Composed of bundles of collagen fibers running parallel to the surface of the eye. |
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Term
| what is the name of the area between the cornea and the sclera? |
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Definition
the limbus cornea
it is a vascularized area |
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Term
| what type of epithelium is found in the cornea? |
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Definition
| stratified squamous epithelium |
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Term
| where can myelinated nerves be found in the cornea? |
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Definition
in the stroma
after crossing the bowman's layers, nerves become unmyelinated and extend toward the surface in the intercellular spaces of the corneal epithelium |
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Term
| what is the name of the area that marks the transition from 10 layers to a 2 layered non-sensory retina? |
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Definition
| the ora serrata; also marks the anterior limit of the neuroretina |
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Term
| describe the choroid layer of the eye and its 4 layers |
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Definition
spongy, brownish layer
made up of 4 layers
From inside-out they are:
lamina elastica also known as Bruch's membrane which has five layers.
choriocapillaris - contains capillaries that are essential to the outer layers of the retina (see detached retina below).
vessel layer - contains larger vessels
epichoroid - nearest sclera |
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Term
| what is bruch's membrane and what are its 5 layers? |
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Definition
innermost layer of choroid, in contact with retina-pigmented epithelium
5 layers:
basal lamina of the pigmented epithelium of the retina
collagen fibers
elastic fibers
collagen fibers
basal lamina of the choroidal capillaries |
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Term
| describe the ciliary body of the eye |
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Definition
specialized structure containing smooth muscle in two orientations
suspends the lens by zonule fibers of the zonule of zinn
ciliary processes produce aqueous humor
when smooth muscle contracts, pulls body closer to lens, releases tension on zonule fibers, suspend lens in more spherical (thicker) shape for near vision (natural state if muscles weren’t attached)
when smooth muscle relaxed, ciliary body gets further away from lens, increase tension on zonule fibers, suspend lens in more flattened, stretched shape for distant vision |
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Term
| what nerves innervate the ciliary muscles? |
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Definition
innervated by postganglionic parasympathetic axons from the ciliary ganglion
The preganglionic neurons are found in the Edinger-Westphal nucleus of the oculomotor complex (you'll get this in neuroscience). The muscles are involved in the accomodation reflex |
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Term
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Definition
The most anterior part of the vascular coat or uveal tract.
Iris means rainbow and the color of the iris varies from individual to individual and with age
Eye color is determined by the numbers of melanocytes in the iris.
Relatively few results in blue eyes.
Many melanocytes result in dark brown eyes.
Intermediate numbers result in green or gray eyes. |
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Term
| the central aperture of the iris is the ______. |
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Definition
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Term
| what is the constrictor pupillae muscle and what innervates it? |
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Definition
The constrictor pupillae muscle (CPM) is smooth muscle innervated by postganglionic parasympathetic fibers from the ciliary ganglion.
The preganglionic neurons are found in the Edinger-Westphal nucleus of the oculomotor complex in the midbrain |
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Term
| what innervates the dilator pupillae muscle? sympathetics or parasympathetics? |
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Definition
sympathetics
if unopposed action, then there is a fixed and dilated pupil which does not respond to light |
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Term
| describe the innervation and the type of cells found in the dilator pupillae muscle |
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Definition
The dilator pupillae muscle is innervated by postganglionic sympathetic fibers from the superior cervical ganglion. The preganglionic neurons are in the intermediolateral cell column of the T1 spinal cord.
The cells of the dilator muscle are myoepithelial cells which form an indeterminant layer just anterior to the posterior pigmented epithelium |
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Term
| what is horners syndrome? |
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Definition
Ptosis – drooping upper lid because of paralysis of Müller’s muscle
Anhidrosis – loss of sweating on the affected side
Miosis – small, constricted pupil due to unopposed action of sphincter pupillae muscle |
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Term
| describe the lens of the eye and its characteristics |
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Definition
The lens is normally totally avascular. It derives its oxygen and nutrients from the aqueous and vitreous humors.
The lens is transparent and the plasma membranes of the lens fibers are extremely impermeable, even to small ions, a characteristic believed responsible for its transparency.
The normal state of the lens is thickened, as it would be for near vision.
The suspensory fibers or zonule fibers hold the lens in a flattened state for distant vision |
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Term
| describe the accomodation reflex |
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Definition
Parasympathetics contract ciliary muscles. This reduces tension on the zonule fibers. The lens thickens, its normal state. Pupils constrict as well.
In presbyopia, lens can no longer thicken because it loses its flexibility. Cannot focus on near objects. |
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Term
| what are the 3 parts of the lens of the eye? |
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Definition
| lens capsule, subcapsular epithelium, lens substance |
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Term
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Definition
A cataract is an opacity of the lens.
Cataracts are typically associated with advancing age.
In persons with diabetes mellitus, high glucose or sorbitol levels in the lens stroma draws water into the region and causes cataracts. It can also thicken the lens causing diabetic myopia. |
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Term
| what are the 10 layers of the neuroretina? |
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Definition
1. pigmented epithelium
2. layer of rods and cones or outer segments of rods and cones
3. external or outer limiting membrane
4. external or outer nuclear layer
5. external or outer plexiform layer
6. internal or inner nuclear layer
7. the internal or inner plexiform layer
8. the ganglion cell layer
9. the optic nerve fiber layer
10. the inner limiting membrane |
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Term
| what are the 3 functions of the pigmented epithelium of the eye? |
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Definition
acts to absorb light and prevent reflection that would distort vision.
the storage and release of vitamin A, a rhodopsin precursor
phagocytose the turned-over membrane from the photoreceptor lamellae |
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Term
| what happens during retinitis pigmentosa? |
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Definition
| failure of the pigmented epithelium to remove the membranous debris from the photoreceptor lamellae has been implicated in hereditary retinal dystrophy in rats and may be involved in the human disease retinitis pigmentosa. |
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Term
| describe characteristics of rods |
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Definition
more numerous type (about 130 million)
throughout the neuroretina
involved in twilight vision (low light)
cylindrical outer segments
contain the photopigment rhodopsin
embedded in the pigment epithelium (between processes)
outer segment connected to an inner segment, which contains numerous mitochondria, by a thin neck
outer segment contains approximately 1000 membrane bound discs or lamellae
these discs contain rhodopsin
new lamellae are constantly formed and added to the outer segment
the old lamellae at the rod tip are phagocytosed by the pigment epithelial cells |
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Term
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Definition
many fewer in number than rods (about 6.5 million)
most cones are found in the region of the fovea centralis
cones are important for visual acuity and color vision
cones are similar to rods in appearance, but tapered outer segment - their lamellae are actually infoldings of the plasma membrane |
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Term
| the retina receives oxygen and nutrients from what 2 blood supplies? |
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Definition
Outer layers, pigmented epithelium and receptors are supplied via the choriocapillaris in the choroid layer
Inner layers are supplied by branches of the central retinal artery |
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Term
| what are the 2 types of age-related macular degeneration? |
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Definition
Dry ARMD
Approximately 90 percent of patients with ARMD
About 1.8 million in US
Wet ARMD
Approximately 10 percent of patients with ARMD
Most severe
Greatest vision loss
0.2 million in US |
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Term
| what is drusen in dry ARMD? |
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Definition
an accumulation of material between bruch's membrane and the pigmented epithelium
accumulates and pushes pigment epithelium of retina away from the blood supply (choroid) causing blindness |
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Term
| what occurs during a detached retina? |
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Definition
The differential blood supply of the retina results from the way the retina develops from an invaginated optic vesicle
Detachment occurs between the pigmented epithelium and the photoreceptors.
When this happens, the photoreceptors are deprived of oxygen and nutrients and will die. |
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Term
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Definition
| Increased intracranial pressure causes the optic disc or papilla to bulge into the eye. |
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Term
| what are the chambers of the eye? |
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Definition
Anterior Chamber
space bounded by the cornea anteriorly and the lens posteriorly. The lateral border of the anterior chamber is the angle or limbus occupied by the trabecular meshwork (pectinate ligament) through which the aqueous humor is drained to the canal of Schlemm.
Posterior Chamber
bounded anteriorly by the iris, posteriorly by the lens and zonule and peripherally by the ciliary processes.
Chambers contain aqueous humor |
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Term
| describe the production and flow of aqueous humor |
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Definition
aqueous humor produced by ciliary processes, passes through pupil into anterior chamber, drains through trabecular meshwork at iridocorneal angle into scleral venous sinus (canal of Schlemm)
aqueous removed by limbal plexus, a network of scleral veins close to limbus which drain into tributaries of vorticose and anterior ciliary veins |
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Term
| what is glaucoma and what is the most common type? |
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Definition
primary open-angle glaucoma
most common type and is a major cause of blindness
Persons with myopia (nearsightedness) and diabetes mellitus are more likely to develop primary open angle glaucoma.
angle of the anterior chamber appears normal.
caused by slow blockage of the canal of Schlemm.
slow, insidious problem and goes unnoticed by the patient
defects can ultimately be detected in the visual field. |
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Term
| what happens in primary-closed (narrow) angle glaucoma? |
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Definition
rarer
angle of the anterior chamber is blocked by the iris
when the pupil is constricted(miotic), the iris is flattened or stretched and the angle is open
when the pupil dilates (mydriasis) the angle is blocked
closed-angle glaucoma has a rapid progression, i.e. sudden onset, and is an emergency situation
presents as ocular pain, blurred vision and appearance of halos or rings around lights |
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Term
| how does the disc appear in optic cupping? |
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Definition
disc appears enlarged
pale optic disc
can lead to retinal atrophy and neuronal death
increased intraocular pressure |
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Term
| what is the vitreal body? |
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Definition
Transparent gelly-like material that fill large vitreous chamber in the posterior segment of the eye
Homogeneous gel, 99% water
Contains collagen, glycosaminoglycans
Hyalocytes synthesize collagen fibrils and glycosaminoglycans
Helps maintain retina in its appropriate position |
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Term
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Definition
Deposits in the vitreous
Probably aggregates of vitreal proteins
Normally not noticeable, but can be seen if one stares at a white ceiling of wall without trying to focus
Floaters seen as fine dust-like particles moving about
Typically benign and do not interfere with vision
Sudden appearance of many floaters can indicate serious eye disease |
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Term
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Definition
removal of cloudy or bloody vitreous humor
vitreous is replaced with saline |
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