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8/19/2019 Ophtha Mod1 Lec1 Ocular Anatomy Trans 2013
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TOPIC: OCULAR ANATOMY: ORBIT, OCULAR ADNEXA, and EYEBALL
LECTURER: DR. NOEL ATIENZA
TRANS by MICHAEL ACE MACARAIG, RN
ORBIT
Bony cavities which contain the eye
“pear-shaped”- optic nerve as stem
Medial wall: parallel; separated by
sphenoid and ethmoid sinuses
Lateral wall: forms 45 degree angle with
medial wall
7 bones of the Orbit: “SPEL FMZ”Sphenoid, Palatine, Ethmoid, Lacrimal,
Frontal, Maxillary, Zygomatic
Dimensions: Height= 35mm
Width=45mm
Diameter= 40-45mm
Volume=30mL
Roof of the Orbit – contains:
Orbital plate of Frontal bone which
contains the lacrimal gland fossa Lesser wing of Sphenoid bone
which contains the optic canal
Fovea trochlearis: pulley for the superior
oblique muscle; located 4mm from orbital
margin
Medial Orbit Wall: contains lacrimal sac
and nasolacrimal canal; referred to as
“lamina papyracea” or paper thin
Composed of: “MELL”= Maxillary,
Ethmoid, Lacrimal and Lesser wing
of Sphenoid bones Lateral Orbital Wall: formed by Zygomatic
and Greater Wing of the Sphenoid bones;
THICKEST and STRONGEST wall
Lateral Orbital Tubercle: Site of attachment
for:
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ligament of lateral rectus
muscle
Suspensory ligament of the
eyeball
Lateral palpebral ligament
Aponeurosis of the levator
ligament
Floor of the Orbit
The “roof” of Maxillary sinus
Made up of 3 bones: “MOP”:
Maxillary, Orbital plate of
Zygomatic bone, Palatine bone
Contains Orbital groove
continuous to become the
Orbital foramen
Inferior oblique muscle: this
arises from the orbital floor; the
only extraocular muscle that
will not originate from the
orbital apex
Orbital Apex
Entry portal for nerves and BVs
Contains the Superior Orbital
fissure and Annulus of Zinn, the
site where all Extraocular
muscles (except Internal
Oblique) originate
Contents of the Orbital Apex:
1. Lateral wall: outside of Annulus of
Zinn
Contents: CN 5- lacrimal and frontal
branch; CN 4-trochlear nerve
2. Medial wall: within the Annulus of
Zinn
Contents: CN 3- superior and inferior
divisions; CN 5- nasociliary branch;
CN 6- Abducens nerve; Superior
Ophthalmic vein
3. Inferior Orbital fissure
Contents: Pterygoid and Maxillary
parts of the CN 5; Inferior
Ophthalmic vein
4. Optic canal; contains the Optic nerve
and Ophthalmic artery
___________________________________
Blood supply of the Orbit
Ophthalmic artery- first major branch of the
Internal Carotid Artery
5 Major Branches:
1. Central retinal artery
2. Lacrimal artery
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3. Muscular branches of the
extraocular muscles- anterior ciliary
artery
4. Medial palpebral arteries
5.
Posterior ciliary arteries
Central retinal artery: enters optic
nerve 8-15mm behind the globe
Lacrimal artery: supplies the lacrimal
gland and upper eyelids
Anterior ciliary artery: supplies the
anterior sclera, episclera, limbus,
conjunctiva and contributes to the
major arterial circle of the iris Medial palpebral artery: supplies the
eyelids
Posterior ciliary arteries:
1. Long - Supply the
ciliary body;
anastomose with
each other to form
the major arterial
circle of the iris2. Short - Supply the
choroid and the optic
nerve head
Venous drainage:
Superior and Inferior
Ophthalmic Veins
Drains the Vortex veins, the
anterior ciliary veins and the
central retinal vein; communicateswith cavernous sinus
OCULAR ADNEXA
Eyelids: Outer structures that
protect the eyeball; contains
Meibomian glands (within the
tarsus) which lubricate the surface
Palpebral fissure – space between the two
open lids
Presence of infection (folliculitis or acne)
around the area is considered an
emergency.
Interpalpebral fissure: Exposed zone
between the upper and lower eyelids;
measures between 8-11 mm in width and is
27mm long
Upper eyelid is more mobile than lower
eyelid. Can be raised up to 15mm by the
levator palpebrae
8 Segments of the Eyelid:
1. (1) Skin:
Thinnest in the body
Eyelid fold: due to insertion of
levator aponeurosis near the upper
border of the tarsus (may not be
present in Asians)
2. Subcutaneous connective tissue
Has no fat content; May swell due to
fluid accumulation or hemorrhage
3. Lid Margin: Punctum
“gray line” (corresponds
histologically to the most superficial
part of the orbicularis oculi muscle
(muscle of Riolan)
4. Orbicularis oculi muscle:
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Arranged in a concentric band
around the interpalpebral fissure
Divided into 2 parts:
a. Orbital: Inserts into the
medial canthal tendon,orbital rim and corrugator
supercili muscle
b. Palpebral : May be voluntary
or involuntary (for normal
and reflex blinking)
5.
Orbital septum: Extension of the
periosteum of the roof and floor of the
orbit; Attaches to the anterior surface
of the levator muscle; Provides a barrier
to spread of blood or inflammation
6.
Levator muscle: Originates from a
tendon that blends with the superior
rectus and superior oblique muscles at
the apex of the orbit
Divides to form: Levator aponeurosis
which produces eyelid fold and
Mueller’s muscle or Superior Tarsal
muscle which elevates the eyelids,
innervated by CN 3
7.
Tarsus: Consist of dense connective
tissue not cartilage; Attached to the
orbital margin by the medial and lateral
palpebral ligaments
Meibomian glands: Modified holocrine
glands --> oily layer of the tear film
8.
Conjunctiva
Blood supply:
Arterial:
Facial system:
Derived from the ECA
Gives rise to the angular artery
(important landmark in DCR surgery)
Venous drainage:
Superficial/pretarsal system:
Drains into the internal and external
jugular veins
Deep/post-tarsal system:
Drains into the cavernous sinus
Accessory Eyelid structures:
Plica Semilunaris : Narrow, highly
vascularized, crescent-shaped fold of
conjunctival tissue
Rich in goblet cells
Analogous to the nictating membrane
Caruncle:
Small, fleshy, ovoid structure
Contains sebaceous glands and fine
colorless hair
LACRIMAL GLANDS and EXCRETORY
SYSTEM
LACRIMAL GLAND-exocrine gland
Located in the frontal bone
Divided into 2 parts by the levator
aponeurosis
Palpebral gland and Orbital
gland, may occasionally be
connected by as isthmus
Serous secretion from 2 types of cells:
Acinar: line the lumen
Myoepithelial: surrounds the
parenchyma
Blood supply: lacrimal artery
Accessory Glands:
Located in the eyelids
Glands of Krause and Wolfring:
produce basal tear secretion
Lacrimal Excretory System
Consists of:
• Lacrimal punctum
•
Upper and lower
canaliculi
• Common canaliculus
•
Nasolacrimal sac
•
Nasolacrimal duct
-eye drops instilled can be tasted by
patient due to nasolacrimal path
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TEAR FILM
Characteristics:
Provides a smooth optical
surface at the air-eye interface
Serves as a medium for removal
of debris
Supply oxygen to the cornea
Protective (antimicrobial and
lubricating properties)
“tri-laminar” structure:
(1) Anterior, lipid layer “oily layer”
Comes from the meibomian glands
30 to 40 in the upper lid
20 to 30 in the lower lid
Function:
Optical clarity
Hydrophobic barries (preventsoverflow/ hold water until next blink)
Slows down evaporation,lubrication
(2)Middle, aqueous layer
Secreted by the main lacrimal
glands and by the accessory
lacrimal glands of Wolffring and
Krause
Consists of electrolytes and
proteins
Function:
•
Supplies oxygen
• Antibacterial
•
Smoothens minor
irregularities
• Washes away debris
(3) Posterior, glycoprotein layer “mucus
layer”
Converts the epithelium from
hydrophobic to hydrophillic -->
allows for even distribution of
tears
Lowers surface tension -->
better stability of the tear film
layer (even when eyes open)
Secreted by the conjunctival
goblet cells and by the
accessory lacrimal glands of
Henle and Manz,; when
sleeping, the secretion of
mucus is low (kaya nagmumuta)
EXTRAOCULAR MUSCLES:
Six muscles per eye
4 recti muscles
Superior rectus-elevator;intorter
Inferior rectus
Medial rectus
Lateral rectus
2 obliques
Superior oblique-intorter
Inferior oblique-extorter
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Muscle
Medial Rectus
Inferior Rectus
Lateral Rectus
Superior rectus
Superior Oblique
Inferior Oblique
Origin
Annulus of zinn
Annulus of zinn
Annulus of Zinn
Annulus of Zinn
Annulus of Zinn
Orbital floor
Insetion
Medially, 5.5mm from limbus
Inferiorly, 6.5 mfrom limbus
Laterally, 6.9mm from limbus
Superiorly, 7.7mm from lmbus
To trochlea atorbital rim, theninferior and
under superiorrectusPosterior inferiortemporalquadrant at thelevel of themacula
Blood Supply
Inf. Muscular branch ofophthalmic artery
Inf. Muscular branch ofophthalmic arteryand infraorbitalarteryLacrimal Artery
Superiormuscular branchof ophthalmicarterySuperiormuscular branchof ophthalmic
artery
Inferior branchof ophthalmicand infraorbitalartery
Size
40.8mm long,1.3mm wide
40 mm long,9.8mm wide
40.6 mm long,9.2 mm wide
41.8mm long,10.6 mm wide
40.0mm long,10.8mm wide
37 mm long, 9mm wide
‘know the insertion of muscles
‘Closest is the medial rectus, farthest is
the superior rectus-need to know when
operating pts with squint/ duling
Blood Supply:
Muscular branches of the
ophthalmic artery
Lateral rectus and inferior
oblique are also supplied by
lacrimal and infraorbital
arteries respectively
•
Except for the lateral
rectus, each muscle is
supplied by 2 anterior
ciliary arteries
Nerve Supply:
CN III: innervates superior,
medial, inferior rectus muscles
and the inferior oblique
CN IV: innervates the superior
oblique
CN VI: innervates the lateral
rectus- for abduction
Choroid is mesodermal in origin
CONJUNCTIVA
Thin, transparent vascular tissue
3 zones:
lines the inner aspect of the
eyelids (palpebral conjunctiva)
covers the sclera (bulbarconjunctiva)
Fornix – junction of the
palpebral and bulbar
conjunctiva (forniceal
conjunctiva)
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Vascular supply is through the anterior
ciliary artery
Innervated by the 1st division of CN V
(ophthalmic division)
Layers:
(1) Conjunctival epithelium
•
2-5 layers of stratified,
columnar epithelial
cells
• Superficial epithelial
cells:
Contains
mucoussecreting
Goblet cells
•
Basal epithelial cells -
contain pigment
(2) Conjunctival stroma
•
Adenoid layer
Lymphoid
tissue
Does not
develop until
2nd or 3rd
month of life
•
Fibrous layer
Connective
tissue
•
Accessory lacrimal
glands (Glands of
Krause) : mostly in
lower fornix
TENON’S CAPSULE: b/w conjunctiva and sclera
Fibrous membrane that envelops the
eye from limbus to the optic nerve
Contributes to the “Check Ligaments”
Tubular reflections of tenon’s
capsule over the EOM’s
Limits the action of the EOM’s
Forms the “Lockwood’s
Ligament” Suspensory ligament of the
globe (eye)
Lockwood’s: fusion of the tenon’s with the
fascia of the inferior rectus and the inferior
oblique
SCLERA: beneath tenon’s capsule is episclera
Thick outer coat of the eye
Normally white and opaque
Becomes red/clear in inflammatory and
infectious conditions-at risk for perforation
Episclera: thin, elastic layer covering the
sclera; provides nourishment to sclera
Avascular, fibrous, outer, protective
coating of the eye
Continuous with the cornea anteriorly
and with the dural sheath of the optic
nerve posteriorly
Lamina cribosa: scleral fibers that pass
through the optic nerve; acts like a
sieve
0.3 mm thick where the EOM’s insert
and about 1 mm thick elsewhere
Composed of:
o Bundles of collagen, fibroblasts
and ground substanceUnlike cornea, contains more water and fibers
are less uniformly arranged
CORNEA
Transparent front “window” of the eye
Major refractive surface of the eye; part
treated by corrective lens
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Loss of transparency in infectious and
inflammatory diseases
“window” of the eye
o Transparency is secondary to:
Uniform structure
Avascularity
Deturgescense
(continuous dehydrated
state due to endothelial
pump)
-contact lenses impair O2 delivery in the cornea
Composed of 5 layers:
Epithelium
Bowman’s Membrane
Stroma
Descemet’s Membrane
Endothelium-most important
Nourished by
the precorneal tear film layer --
> oxygen --> epithelium
Aqueous humor --> glucose -->
stroma and endothelium
Corneal Epithelium:
5 to 6 layers
•
basal columnar cells
•
polygonal cells (“wing
cells”)
• a superficial layer -
nonkeratinized
stratified squamous
cells
Is attached by
hemidesmosomes
Hydrophobic
• Due to its lipid content
Bowman’s membrane: acellular; cannot
regenerate
o
Forms a scar after injury
o
Barrier to most molecules
Stroma: 90% of corneal thickness
o
Cells found are fibroblasts
(keratocytes); regular arrangement of
collagen fibers makes the cornea clear
Descemet’s membrane: basement membrane
of corneal endothelium
o Hassal-Henle bodies: metabolic by-
products of Descemet’s membrane
located peripherally
Corneal Guttata
o Central excresences (look like bubbles
in the central cornea)
Fuch’s Endothelial Dystrophy -cause of
congenital visual loss
o
Endothelial cell loss --> loss of visual
acuity
Corneal endothelium: derived from neural
crest; 1 million cells at birth
o Lined by single row of hexagonal cells
o Apex attached to anterior chamber
o Base attached to descemet’s
membrane
o
Functions as a barrier between the
stroma and the aqueous and as a
pump to maintain the cornea in a
partially dehydrated state
LIMBUS: peripheral part of cornea
The junction between cornea and sclera
May develop whitening as part of old
age
Arcus senilis: Often mistaken as
cataract; does not affect vision
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surgical landmark
structures included in limbus:
Conjunctiva
Tenon’s capsule
Episclera
Corneoscleral stroma
Aqueous outflow apparatus
INTERNAL OCULAR STRUCTURES
Anterior chamber
o
The space between the cornea and iris
o
Contains a watery fluid called aqueous
humor
o
Normally acellular
o
Cells seen in inflammatory and
infectious conditions
o Important structures: used to
determine if patient has narrow/
closed chamber angle (1 and 2)
Schwalbe’s line (1)
Marks the termination of the corneal
endothelium
Schlemm’s canal and the trabecular
meshwork
Drains the aqueous from the anterior
chamber
Scleral spur
Inward extension of the sclera
between the ciliary body and
Schlemm’s canal: where iris and ciliarybody are attached
Anterior border of the ciliary body
Iris
Uveal tract
o Middle, vascular layer of the eye
o Contributes to the blood supply of the
retina
o Composed of:
o
Iris
o Ciliary body
o
Choroid
IRIS
o
Anterior extension of the ciliary body
o
Colored part of the eye that screens
out light
o Pigmented posterior surface
o Accounts for the variety of eye colors
seen
o Dependent on the amount of pigment
in the iris
o Composed of:
o Blood vessels, connective tissue,
melanocytes and pigment cells
o
parasympathetic activity transmitted
via the CN3 and dilation due to
sympathetic activity
o sensory innervations is by ciliary nerve
PUPIL
Circular opening at the center of the iris
Adjusts the amount of light entering the
eye
CILIARY BODY
Structure of the eye that produces
aqueous humor
Contraction of the ciliary body
Changes the tension of the
zonular fibers suspending the
lens
Most important function is to
determine the amt of tension
on zonular fibers that willaffect the refractive state of
the eye (where we focus)
If a person less than 40 y/o cannot
focus near or far, it may be due to
cataract. Lens is more spherical in near
vision (zonular fibers are more relaxed)
and flatter when in far vision
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2 parts:
Pars plicata: anterior corrugated zone
Gives rise to Ciliary Processes -->
produces the Aqueous Humor
Pars plana: flattened, posterior zone
Lining:
Internal non-pigmented layer --
> represents the anterior extension of
the neuroretina
External pigmented layer --> represents
the extension of the retinal pigment
epithelium
Ciliary muscle:
o Composed of longitudinal,
circular and radial muscles
o
Circular muscles --> contract
and relax the zonular fibers
o Alters the tension on the
capsule of the lens
o
Allows the lens to give variable
focus for distance and near
o
Longitudinal Muscles --> insert
into the trabecular meshwork
CHOROID
Nourishes the outer retina
Composed of 3 layers of blood vessels
innermost
layer/choriocapillaries
•
fenestrated
Middle layer
Outer layer
Bruch’s Membrane- internal boundary
of the choroid, serves as barrier
LENS
Biconvex structure
Is nourished solely by the aqueous and
vitreous
Enclosed by a Capsule
Semi-permeable membrane
Product of the lens epithelium
Anterior capsule is 2 times
thicker than the posterior
capsule
Zonule of Zinn
Composed of fibrils that arisefrom the ciliary body and
inserts at the lens equator
Holds the lens in place
In surgical lens implantation, posterior capsule
is preserved.
VITREOUS-contains 4.5cc of gel material
Characteristics:
Clear, avascular, gelatinous
body
Comprises 2/3 of the volume of
the eye
99% water, 1.0% collagen and
hyaluronic acid
Vitreous floaters (parang
sinulid) – seen in miotic eyes,
usually in old people (50-60)
Hyaloid membrane:
Outer surface of the vitreous
In contact with posterior
capsule, zonules, pars plana,
retina, optic nerve head
Vitreous base:
Where the vitreous is firmly
attached to the retina
Posterior Vitreous Detachment
Separation of the vitreous from
the inner retina
Seen as a ring in the vitreous
(examiner)
Occurs with age
Associated with retinal
detachment
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RETINA
Layers: Inside going out:
1.
Inner Limiting Layer
2.
Inner Limiting Membrane
3.
Nerve Fiber Layer4.
Ganglion Layer
5.
Inner Plexiform Layer
6.
Inner Nuclear Layer
7.
Outer Plexiform Layer
8.
Outer Nuclear Layer
9.
External Limiting Membrane
10.
Layer of Rods and Cones
Optic nerve fibers are connected to Nerve fiber
layer
Initial processing of light: rods and cones
Retinal pigment epithelium
Functions:
Vitamin A metabolism, maintenance of
the outer blood-retinal barrier,
phagocytosis of the photoreceptor
outer segments, absorption of light,
heat exchange, formation of the basal
lamina,production of
mucopolysaccharides, active transport
Adjacent RPE cells are attached to each
other by junctional complexes which
provide both structural and metabolic
stability (outer blood-retinal barrier)
Zonula occludentes and Zonula
adherents:Thickest at the
Papillomacular Bundle and thinnest at
the Fovea
MACULA
Area of the retina responsible for fine,
central vision
Fovea
o oval depression in the center of
the macula
o
Approximately 2 disc diameters
away from the optic disc
o
Slight inferior to the optic disc
Foveal reflex – light reflection at fovea
seen during ophthalmoscopy
Macula: Located in the area of the temporal
vascular arcade; most important part of the
retina as far as central vision is concerned
because it contains most cones, (rods are
important for peripheral vision in contrast)
OPTIC NERVE (extension of CNS)
Corresponds to the “blind spot”
in perimetry
Intraocular portion is termed
optic disc/ optic nerve end
Intraorbital portion- visualized
thru CT scan/ MRI: connected
to the optic chiasm
Intracannalicular portion: very
important because gets easily
compressed by tumors.
Glaucoma: ganglion cell layer
disease- enlargement of optic
cup; normal cup-disc ratio: 0.2-
0.6
“Sacrifice may be bitt er, but the
fruit of success is sweet”