ophtha mod1 lec1 ocular anatomy trans 2013

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”

ophtha mod1 lec1 ocular anatomy trans 2013

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