Structures surroundingthe eyeball; including eyelids, eyebrows, tear drainage system, orbital walls and orbital contents
Structures of the eyelids, conjunctiva, landmarks, eyelashes, and eyebrowsare?
Moving folds of skin covering the outer portion of the anterior eyeball
Eyelids functions include?
from foreing body and bright light
Protects cornea from DESSICATION (drying out) by blinking action
What purpose does blinking have?
Spreads the tears over the eye surface
Protects eye,natural reation to blink
Aids in the flow of tears out of the lacrimal gland
Aids aspiration of tears into the nasolacrimal system
The palpebral fissure is what?
The opening between the upper and lower lids
What is the medial canthus?
The point on the nasal side of the palpebral fissure where the lids meet.
What is the caruncle?
The small reddish protuberance consisting of an island of skin containing sebaceous and suderiferous glands over the semilunar fold (plica semilunaris), source of white secretion that is constantly being produced.
What is the plica semilunaris?
Semilunar fold,. Is a crescent shaped strip of tissue that borders the caruncle lateraly; contains some smooth muscle fibers,and is part of the conjunctiva
What is the lateral canthus?
Is the temporal (outter junction) corner of the eyelid opposite of the medial canthus.
What is found in the lateral canthus?
There is no significant structures found here..
What are eyelashes or cilia and what purpose do they serve?
Are relatively short hairs growing from the margin of each eyelid.
Approximately 100-150 in each upper lid and about half that in lower lid.
serve to protect the eye from foreign objects.
What can be seen in a cross section of an eyelid?
Orbicularis oculi muscle
Follicles of cilia
Opening of the meibomian gland
Levator palpebra superioris
What are the 7 layers of the eyelid?
2Subcutaneous connective tissue
4Submuscular connective tissue
First layer of the eyelid is?
Second layer of the eylid is?
Subcutaneous connective tissue.
Loses elstisity with age causing lids to droop
Third layer of the eyelid is?
Orbicularis oculi, levator palbebral
Forth layer of the eyelid is?
Submuscular connective tissue
Connects to the taral plate
Fith layer of the eyelid is?
Sicth layer of the eyelid is?
Tarsal plate or fibrous layer
Dense plate-like framework within upper and lower lids provide stiffness and shape
Aids in protection of the eye
Place for muscle attachment
Contains Meibomian glands
Seventh layer of the eyelid is?
Inner layer of the lid
Connects with Bulbar conjunctiva
What muscles are within the lid?
Muscle sheet surrounding the eye that closes the eyelids, gently by the Palbebral portion as in blinking, tightly by orbital portion as in crying or sneezing
Inervated by the 7th cranial nerve facial cranial nerve
Levator palpebral superioris
Primary elevating muscle, its contraction accompanies that of superior rectus
Originates at the rear of the orbit in the annuals of Zinn, comes forward above superior rectus-
Inserts into the upper eyelid
Innervated by the upper divisio of the 3rd cranial nerve, occulomotor cranial nerve
Helps Orbicularis close lid,located behind the eyelashe Follicles, helps the inner lid margin hug close to the eyeball
Innervated by the 7th cranial nerve. Facial cranial nerve
Smooth involuntary muscle (controled by sympathetic nerves) found in the upper and lower lids
Assists in elevation of upper lid
In the upper lid originates from undersurface of levator muscle and attaches to superior margin of tarsal plate
In lower lid it arises from the inferior rectus
Causes slight retraction of lower lid
Glands of the eye include?
Krauss and Wolfring
Glands of Zeiss
Glands of Moll
Large sebaceous gland(oil) located in the tarsal plate of each eyelid (lipid)
30 in each tarsus
Oily secretion of glands coats the tear layer over the cornea and prevents rapid evaporation of tears and spillage of tears over the margin of the eyelid
Is first layer of tear film
Primary glands for producing watery layer of tears
Accessory glands of Krauss and Wolfring
Lacrimal glands found in the eyelids that add thier watery secretions to those of the primary lacrimal glands
Glands of Zeiss
Oil producing gland that surround the eyelashes
Ducts enter lash Follicles near the eyelid margins
Glands of Moll
Sweat glands located near the base of the eyelashes
Large superficial mucus glands in the conjunctiva that secrete mucinwhich contributes to the pre-corneal tear film, moistening and protecting conjunctiva and cornea, absent or damanged in dry eye syndrome.
Thin translucent mucous membrane that lines the innner surface of eyelids and covers the outer anteriorsurface of sclara
Palbebral conjunctiva is?
Is the portion lining theninner surface of eyelids this portion is thick, opaque, and highly vascular
Bulbar conjunctiva is?
The tissue covering anterior sclara, is thin, transparent, slightly vascular
The lacrimal system consists of what?
Produces watery layer of tears which is second or middle layer of the tear film
Located in the superior lateral corner of each orbit, just under superior lateral rim
Each gland has 6-12 ducts emtying secretions into superior fold of the conjunctiva
Found in the Palbebral conjunctiva produces mucinous fluid that forms the third or innermost layer of tears
Promotesb adherence of the tears to the eye for more even distribution of the tear film over the cornea and conjunctiva
Upper and lower puncta
Small openings in the medial margin of each eyelid near the nose,excess tears froma meniscus or lacrimal lake along the lower lid margin
With each blinking action of the eyelids, tear fluid the lacrimal lakes is pushed into the puncta
Upper and lower canaliculi, is a small lacrimal duct or opening that starts at the lacrimal puncta.
A short distance beyond the medial aspect of the caruncle they come together and form an expanded sac, lacrimal sac.
Is the expanded sac into which the lacrimal ducts join and empty the tears
It is all lateral to the nasal cavity.
Membranous canals extending from the bottom of the lacrimal sac to the inferior meatus of the nasal cavity
Tears empty into nasal cavity and become a part of the fluid that moistens the mucous membrane of the nose
Nasolacrimal duct and lacrimal sac are also lined with mucous membrane.
What are the bones of the orbit?
Located on nasal side of the orbital floor
Skull bone that forms forehead and orbital roof
Cheek bone forms part of the orbital floor and most of the lateral wall
Bone forming part of the medial orbital wall
Small bone forming the front part of the medial orbital wall
Bone that forms part of the medial floor of the orbit
Smallest of seven bones forming the orbit.
Forms the back part of the lateral and medial orbital wall
What are the componants to the orbital features?
Supirior orbital fissure
Inferior orbital fissure
Roof consists of?
Portions of the frontal and lessorwing of the sphenoid bones
Floor consists of?
Portions of the maxilla, Zygomatic, and Palitine
Medial wall consists of?
Portions of the maxilla, lacrimal, and Ethmoid
Lateral wall consists of?
Portions of the Zygomatic and greater wing of the sphenoid
Also known as aditus orbitea
Large opening at the fron of the orbit
Formed by the rim or margin of the orbit,anteriorlt
Area where the walls of the orbit come to a point posteriorly
The optical foraman is found here
What bones are common too both orbits?
Frontal ethmoid and sphenoid
Meaning they are the same bone fhat form the particular part of the orbit but because of the location of the bone form the coresponding portion of each orbit
Small circular canal at the apex of the orbit
It is contained in the lessor in the lessor wing of the sphenoid bone
The optic nerve and opthalmic artery enter the orbit through here
Supirior orbital fissure
Opening near the apex of the orbit between the greater and lessor wing of the sphenoid bone
The oculomoter nerve, trochlear nerve,opthalmic devision of the trigeminal nerve, and the abducens nerve enter the orbit through this fissure
The recurrent branch of the lacrimal artery enters and the opthalmic vein exits through this fissure
Inferior orbital fissure
Small openinglocated located in the greater wing of the sphenoid bone and the orbital surface of the maxilla
The infraorbital artery, infraorbital vein,branches of the inferior opthalmic vein, the maxillary devision of the trigeminal nerve, and the Zygomatic. Nerve enter and exit through this fissure
Fibrous lining that lines the inside of the orbit
Provides an anchor for attachment of muscular fascia
fibrous lining that covers the bulbous oculi
Provides a place of attachment for the EXTRA OCULAR MUSCLES
fibrous lining that covers the extr-orbital muscles
What are fissures?
Narrow crack like openings
What is a foramen?
A hole like opening through a bone
What is a fossa?
An indentation or depression in a bone
Fossas of the orbit include?
Lacrimal gland fossa
Lacrimal sac fossa
What are the extra-ocular muscles?
There are a total of 6
What are the six muscles responsible for?
For eye movements are identified by their position position of insertion to the globe
There are four
Originate from the apex of the orbit and travel anteriorly past the equator to attach to the eyeball a few mm behind the limbus
Located along the supirior wall of the orbit similar to inferior rectus in that it only makes 23* angle with the medial wall
elevation and rotates the eye upward toward the frontal bone
adduction and intorsion
by branch of the Oculomoter nerve cranial nerve III
Located along the floor of the orbit, makes a 23* angle with the medial wall of the orbit
depression of the eye, rotating it downward toward maxillary bone
adduction and extorsion (rotation of the eye toward the temple)
By the branch of the Oculomoter nerve cranial nerve III
Extends from its origin along the medial wall of the orbit to its insertion point
Most powerful extr-ocular muscle
adduction (turning the toward the nose ) is its only action
Inferior branch of oculomoter nerve cranial nerve III
Travels along the lateral wall of the orbit
abduction (rotates eye toward temple and away from midline
by the abducens nerve cranial nerve VI
Originates. In the apex of orbit on the annulus of Zinn or near it on the lessor wing of the sphenoid bone, travels along the supirior wall to the TROCHLEA where the ligament of the muscle passes through and ends at thr insertion point on the behind or posterior to the equator. The ligament of the supirior oblique makes on angle of 51* to 53* with the medial wall
intorsion (rotation of the top of eye toward noxse and bottom away from nose)
depression, turning the eye downward toward the maxillary bone
by trochlear nerve cranial nerve. IV
Originates at the front of the orbit at the inferior medial aspect just inside the rim of fossa, it travels laterally and posteriorly to attach to the inferior surface of the eyeball beneath the inferior rectus and posterior to the equator
SECONDARY and TERTIARY ACTION
elevation and aduction
by the oculomoter nerve cranial nerve III
Which of the extr-ocular muscles is the only muscle that originates at the front of the eye?
Inferior oblique muscle
LR6SO4 all the rest are 3
Cranial nerve inervation.
Lateral rectus cranial nerve VI abducens
Superior oblique cranial nerve IV trochlear
Medial,inferior,superior recti muscles cranial nerve III oculomoter
Whar is a trochlea?
A ring likestrucrue of fibrocartilage attached to the frontal bone through which passes the tendon of the superior oblique muscle
Tunics of the eye?
Fibrous tunic is formed by?
Sclera and cornea form the fibrous tunic
Protection and shape inregrity
Central outer most anterior portion
Thinstrong transparent membrane made up of 5 layers
Serves as the most powerful refractive structure
2nd layer of refraction Tear Layer is 1st
Anterior to posterior what are the five layers of the cornea?
Transparent tissue made of fibers runing parallel to surface
easily destroyed never regenerates
Composed of layers of interlaced collaen fiber bundles running parallel to surface
Makes about 90% of corneal mass
Encases sensory nerves (trigeminal) of cornea
Layer bordering the inner surface of stroma
Contributes to rigidity.
Single cell layer lining Descements
Inner most layer in contact with aqueous humor
Acts like pump to maintain proper fluid balance in cornea
Transports nutrients to cornea
White part of eye
Covers 5/6ths of eyeball
Opque and covered in conjunctiva
Junction between sclera and cornea is called LIMBUS
Insertion place for all six Extra-ocular muscles
Also called uveal tract
COMPRIED OF THE FOLLOWING
Ring like muscle tissue streches over back part of anterior chamber behind cornea
Most anterior portion of vascular tunic
Regulate amount of light by altering pupil size
Iris consists of?
Sphincter muscles arranged in circular, purse string fashion
Dilaror muscles arranged around the constrictor muscles in a radial manner
Melanin pigment of iris amount of melanin detirmines color of eye
Space between the corneal endothelium and front part of iris
Space between the back of iris and anterior portion of vitreous
Located imediately behind iris
Encircles inside of sclera toward front of eye
Band like structure of muscle
Alter shape of crystalline lens
Contains Ciliary process and Ciliary muscle and suspensory ligaments or Zonules
Are the inner folds,rows or ridges on inner surface of sclera toward front of eye
Band like structure made of muscle and secretory tissue
Rings of smooth involuntary muscle lying against the inner surface of the anterior portion of sclera
Muscles contract-relaxes tension on Zonular fibers and crystalline lens allowing it to become more spherical
Muscles relax- tension on lens increases causing it to flatten
Suspensory ligaments or Zonules
Referred to as Zonules of Zin
Connect lens to Ciliary body
Third part of Uveal tract
Layer. Of tissue continuous with Ciliary body
Lies between sclera and retina
Contains melanin, helps abosorb light coming into the eye after it has stimulated the photoreceptors
Anterior chamber angle or filtration angle
Area formed by junction of cornea and iris
Trabecular meshwork or Trabeculum
Canel of Schlemm
Trabecular meshwork. Or Trabeculum
Drainage system formed by large number of small openings in the inferior surface of cornea at cornealscleral angle
Canel Of Schlemm
Circular conduit surrounding Trabeculum and communicating with it
Aqueous fluid drains into canel
then drains into small blood vessels on surfaceof eye and returns to circulatory system
Also called corneoscleral junction
Palpebral conjunctiva begins and bulbar conjunctiva ends
Transparent layer forms inside lining of globe
Considered to be extdnsion of brain
Ten layers mostly nerve cells
Contains light receptors rods and cones
Pars optica retina
Macula or macula lutea
Area anterior of ora serrata which is actually Ciliary body
Contains no rods or cones
Anterior part of Ciliary body is pars plica
Circular line that makes the seperation between the pars optica. And pars ciliaris
Pars optica retina
Largest part of retina
Contains rods and cones
Lines inner surface of Choroid
Central area of retina
Portion of retina used for central vision
Small depression in retina located at center of macula
Responsible for fine dircrimination and sharpest visual acuity
Contains only cones
What is foveal reflex?
When examined with opthalmicscope light is reflected so examiner will see a small bright spot of light
Circular area on the retina medial to macula
Area where one million nerve fibers exit globe along with retinal artery and vein
Physiologic blind spot due to no rods or cones in this area
Specialized nerve endings that produce an electrical nervous impulse when stimulated by light
Rods and cones
Rod shaped with flat outer segments aprox 120 million per eye
Contain chemical Rhodopsin(visual purple)
reacts to light and triggers nerve impulse
Responsible for black amd white vision night or low light vision (scoptic vision)
Pointed or cone shaped oure segments aprox 6 million per eye
Contain three seperate chemicals each responsible for a different color blue red or green
Less sensative to light the rods
Responsible for color vision and visual acuity
Function bset in bright light
Refractive medias of the eyeball
1 tear film
3 aqueous humor
5 vitreous humor
Tear film is 3
Meibomian gland. Lipid
Lacrimal and accessory glands Krause and wolfring. Watery layer
Goblet cels. Mucus layer
Clear watery fluid prodeuced by Ciliary body to nourish lens and posterior side of cornea
Gel like substance encased in vitreous membrane between crystalline lens and retina
Main components are
Central retinal artery
Central retinal vein
Uveal tract(vascular tunic)
Enters via optic foramen
Provides practically all blood suply to orbit and its structures
Exit via superior/inferior orcital fissure.
Drain blood from orbit
Central retinal artery
Supplies blood to retina
Runs through middle of optic nerve branches of Opthalmic artery
Central retinal vein
Drains blood from retina
Runs thrlugh optic nerve branches of opthalmic vein
Supplied by Ciliary blood vessels
Several anterior. Ciliary arteries and two long posterior arteries feed iris, ciliary body,and anterior portion of Choroid
Drained of blood by vortex veins and small posterior ciliary veins
Drain some blood from anterior sclera as well as some aqueous humor from aqueous veins
Found rightnon top of sclera between conjunctiva and sclera
Drain mainly aqueous humor
Originate in choroid drain major ciliary veins
Responsible for draining blood from choroid
Cranila nerve that affect the function and physiology of the eye
Cranial nerves that inervate the eye in some way shape or form
Optic nerve cranial nerve II
Oculomoor nerve cranial nerve. III
Trochlear nerve. Cranial nerve IV
Trigeminal nerve. Cranial nerve V
Abducens nerve.cranial nerve VI
Facial nerve cranial nerve VII
Optic nerve CNII
Transmits visual impulses from rods cones to optic chiasm
Oculomotor nerve CNIII
Sends impulses to superior rectus, inferior rectus, inferior oblique,. Medial rectus, and levator Palpebral superiouris
Trochlear nerve. CNIV
Suplies nerve impulses to superior oblique
Trigeminal nerve. CNV
Transmits pain impulses to brain
Highest concentration of sensory nerve endings is in cornea
Abducens nerve. CNVI
Impulses. To lateral rectus
Facial nerve. CNVII
Sends fibers to lacrimal gland as well as many of facial muscles to onclud orbicularis ocular
Lateral ganiculate bodies
Visual cortx of occipital lobe
Retina in text of visual pathway
Each quadrent sees the exact opposite of the visual field
Macula is at center
Optic nerve head located in the nasal half creates Physiologic blind spot
Rod and cones
Photoreceptors stimulated by light to initiate nervous impulse,transmitted from rods and cones by retinal fibersto optic disc/optic nerve head
Retinal nerve fibers converging on disc and pass out of eyeball forming a bundle or retinal fibers
Optic nerve. Tranmits visual impulses fromoptic disc and optic chiasm
Optic nerve from each eyeball travels medially and posteriorly to meet at the base of the cerebrum where theu form an X shaped structure calledoptic chiasm retinal fibers from the temporal halfremain on that side of the brain,retinal fibers from nasal half cross over to opposite side of the brain the crossover is called decussating
Bilateral groups of decussated nerve fibers
Temporal retinal fibers from the ipsilateral eye
Nasal retinal fibers from the ipsilateral eye
Project posteriorly from the optic chiasmfor a short distance
Thentraval within the brain to end up at the lageral geniculate bodies of the thalumus
Lateral gamiculate bodies
Areas kn the thalmus of the brain where the opticfibers end, new fibers are relayed to the higher level,the occipital lobe of cerebrum by optic radiations
Pathway of the nerve cells from the lateral. Ganiculate bodies to the occipital lobe of cerebrum
Medial aspect of occipital lobe
Specialized for interpretaion of impulse coming from LGB
Wjere visual interpretaion takes place
How we see
Superior visualizes inferior
Inferior visualizes superior
Temporal visualizes nasal
Nasal visualizes temporal
Retinal primary response of rods and cones converting light into impulse
Novisual system felies on different kinds of cells called INTRINSICALLY PHOTOSENSATIVE RETINAL GANGLION CELLS ipRG
irPG cells dont appear to be involved in vision but are directly light sensative and play a crucial role in Pupillary response
Ebven in pts with No Light Preception have Pupillary response
Pupillary pathway has. Two types of pathways?
Takes sensory signal to brain for processing
From retinal irPG cells
To oprtic nerve
Follows vusual pathway throught chiasm and optic tract
Splits befor reaching lateral geniculate body travels to pretectal nucleus
Afferent fibers travel from pretectal nucleus to Edinger-Westphal nucleus. (CN III Oculomotor ) where interpretaion of light from both pretectal nucleus
Stimulated by retinal blur
Begins with rods and cones
Follows visual pathway to visual cortex
From visual cortex to Ediger-Westphal nucleus
Takes motor signal from brain to iris
Identical for both light and accommodation signals
Begins ad Edigner-Westphal nucleus
Signal transmitted throughout CN III Oculomotor
Travels through Ciliary ganglion and to Pupillary sphincter muscle
Pupil testing of efferent pathway reflex
Direct Pupillary reflex
Consenual Pupillary reflex
Accommodative Pupillary reflex
Direct Pupillary reflex. Efferent pathway
A Pupillary constriction in one eye caused when light is shined inthat eye
Consenual Pupillary reflex. Efferent pathway
A Pupillary constriction in one eye when light is shined in opposite eye
Accommodative Pupillary reflex. Efferent pathway
A Pupillary constriction as a result of the act of accommodation
Afferent Pupillary reflex testing
Swinging flashlight test
Compares direct and Consenual. Reflexes in same eye
Gives relative indication of functioning of each eye and optic nerve
Abnormal responseis called relative afferent Pupillary defect inrelation to other eye
Anomalkes of pupil
Difference of. 3mm or greater in pupil size
15-25% of population
Pupils respon normal no medical signifigance may alternate from side to side
Difference between Pupils will be similar under both phototopic and scotopic conditions