lecture1-anatomyoftheeye-101001073534-phpapp02 (1)

8/13/2019 lecture1-anatomyoftheeye-101001073534-phpapp02 (1)

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ANATOMY AND

PHYSIOLOGY OF THE EYE

Department of Ophthalmology

Fatima College of Medicine


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ORBIT

BONY CAVITY WHICH HOUSES THEEYEBALL

4 WALLS - ROOF,FLOOR, MEDIAL ANDLATERAL WALL

30 mL in volume

HAS AN APEX WHERE NERVES ANDVESSELS EMERGE


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Orbital Walls


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ORBITAL WALLS

ROOF

COMPOSED OF THE LESSER WING OF THE

SPHENOID, AND ORBITAL PLATE OF THEFRONTAL BONE

INTIMATELY RELATED TO THE FRONTALSINUS


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ORBITAL WALLS

LATERAL WALL

SEPARATED FROM THE ROOF BY THE

SUPERIOR ORBITAL FISSURECOMPOSED OF THE GREATER WING OF THE

SPHENOID, ZYGOMATIC BONE

STRONGEST PART OF THE BONY ORBIT


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ORBITAL WALLS

FLOOR

SEPARATED FROM THE LATERAL WALL BY

THE INFERIOR ORBITAL FISSUREINTIMATELY RELATED TO THE MAXILLARY

SINUS

COMPOSED OF MAXILLARY BONE,ZYGOMATIC BONE AND PALATINE BONE

ORBITAL CONTENTS CAN HERNIATE INTOTHE MAXILLARY SINUS IN TRAUMA CASES


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ORBITAL WALLS

MEDIAL WALL

INTIMATELY RELATED TO THE ETHMOID

AND SPHENOID SINUSESCOMPOSED OF THE ETHMOID BONE,

SPHENOID BONE, LACRIMAL BONE ANDMAXILLA


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ORBITAL APEX

SERVES AS A PORTAL FOR NERVES ANDVESSELS

SITE OF ORIGIN OF ALL EOMS EXCEPTINFERIOR OBLIQUE


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Orbital Apex


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SUPERIOR ORBITAL

FISSURE

LATERAL PORTION

SUPERIOR OPHTHALMIC VEIN

LACRIMAL NERVEFRONTAL NERVE

TROCHLEAR NERVE

MEDIAL PORTIONSUPERIOR AND INFERIOR DIV. OF

OCULOMOTOR NERVE


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ORBITAL APEX

OPTIC CANAL

TRANSMITS OPTIC NERVE AND

OPHTHALMIC ARTERYSUPERIOR ORBITAL FISSURE

ALSO TRANSMITS THE INFERIOR

OPHTHALMIC VEIN


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BLOOD SUPPLY OF THE

ORBIT

OPHTHALMIC ARTERY

CENTRAL RETINAL ARTERY

LACRIMAL ARTERYMUSCULAR BRANCHES

LONG AND SHORT POSTERIOR CILIARY

ARTERYMEDIAL PALPEBRAL ARTERIES


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Blood Supply of the Eyeball


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BLOOD SUPPLY

SHORT POSTERIOR CILIARY ARTERY

CHOROID, OPTIC NERVE

LONG POSTERIOR CILIARY ARTERYSUPPLY CILIARY BODY, ANASTOMOSE WITH

EACH OTHER AND ANTERIOR CILIARY

ARTERY TO FORM THE MAJOR ARTERIALCIRCLE


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BLOOD SUPPLY

Anterior ciliary artery

derived from muscular branches of the rectus

musclesanterior sclera, episclera, limbus, conjunctiva


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Venous Drainage of the

Orbit

Superior and Inferior Ophthalmic Veins

Vortex veins

Anterior Ciliary Veins

Central retinal Veins


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Venous Drainage of the

Eyeball


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Venous Drainage

The ophthalmic veins communicate withthe cavernous sinus via SOF and thepterygoid venous plexus via the inferior

orbital fissure.The SOV is formed from the supraorbital

and suparatrochlear veins which drain the

skin.* potential communication between skin

infection and cavernous sinus causing

thrombosis


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Eyeball

Roughly spherical

approximately 24.5 mm (less than an

inch) in lengthabout 5mL in total volume


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Eyeball


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Histological Cross Section

of the Eyeball


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Conjunctiva

Thin transparent mucous membranewhich covers the posterior surface of the

eyelid (palpebral conjunctiva) and theanterior surface of the sclera (bulbarconjunctiva)

composed of two to five layers ofstratified columnar epithelial cells

contains glands which help in ocular

lubrication


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Conjunctiva

Blood Supply

anterior ciliary artery

palpebral aretriesNerve Supply

first division of the trigeminal nerve


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Upper Eyelids


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Lower Lid Retractors


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Tenons Capsule

A fibrous membrane that envelopes theglobe from the limbus to the optic nerve

continuous with the EOMsthickens to form check ligaments


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Sclera

Fibrous outer protective coating of theeye

composed of dense bands of wellhydrated connective tissue


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Episclera

Fine elastic tissue containing bloodvessels and covers the anterior surface of

the sclera


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Cornea

Transparent tissue which accounts formost of the refractive power of the eye

thicker at the limbus, and thinner at the

center5 layers

epithelium

Bowmans layer

Corneal stroma

Descemets layer

Endothelium


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Cornea


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Cornea


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Uveal Tract

Iris

Ciliary Body

Choroid

P t i Vi f U l


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Posterior View of Uveal

Tissue


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Iris

Flat anterior extension of the ciliary body

has a central round aparture known as

the pupildivides the anterior from the posterior

chamber


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Iris


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Ciliary Body

Extends from the choroid to the iris

divided into the pars plicata and pars

planapoint of suspension of the lens

produces aqueous humor


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Aqueous Flow


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Choroid

Posterior segment of the uveal tract inbetween the retina and sclera

joins the ciliary body anteriorlychoroidal blood vessels nourish outer

portion of the retina


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Ora Serrata


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Choroidal Circulation


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Lens

Biconvex, avascular, colorless andtransparent structure

second most powerful refractive tissueheld in place by suspensory ligaments

known as zonules

accommodates to facilitate near vision


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Lens Accommodation


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Lens in the Young


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Lens in the Aged


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Anterior Chamber Angle

Schwalbes line

Schlems canal

Trabecular meshworkScleral spur


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Anterior Chamber Angle


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Aqueous Flow


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Optic Nerve Cupping


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Retina

Thin, semitransparent, multilayered sheetof neural tissue

lines the inner aspect of the posterior twothirds of the globe

terminates anteriorly as the ora serrata


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Fundus


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Posterior Pole


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Layers of the Retina

1. Internal limiting membrane

2. Nerve fiber layer

3. Ganglion cell layer

4. Inner plexiform layer

5. Inner nuclear layer

6. Outer plexiform layer

7. Outer nuclear layer

8. External limiting membrane

9. Photoreceptor layer (rods and cones)

10. Retinal pigment epithelium


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Retinal Layers


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Macula

Center of the posterior retina

responsible for fine central vision

has yellow pigment (xantophyll)histologically empty space tends to the

accumulation of extracellular material

that cause thickening


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Photoreceptors


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Blood Supply of the Retina

Choriocapillaries

outer third of the retina

Central Retinal Arteryinner two thirds of the retina


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Embryonic Eye


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Embryonic Eye


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Vitreous

Clear, avascular, gelatinous body

comprises 2/3 of the volume of the eye

99% water ; 1% hyaluronic acid andcollagen

firmly attached to the pars plana and ora

serrata


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Eyeball


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External Anatomic Landmarks

Limbus - point of referance , site ofincision for basic cataract extraction

Ora Serrata - 6mm from the limbus on thenasal side ; 7mm from the limbus on thetemporal side

Pars plana - 4mm from the limbusPars plicata - 2-3 mm from the limbus


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Extraocular Muscles

Rectus Muscles

superior rectus

inferior rectusmedial rectus

lateral rectus

Oblique MusclesSuperior oblique

Inferior oblique


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Extraocular Muscles


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Nerve Supply of EOMS

Oculomotor nerve innervates medial,inferior and superior rectus muscles as

well as the inferior oblique muscleAbducens nerve innervates the lateral

rectus muscles

Trochlear nerve innervates the superioroblique muscle


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Blood Supply of the EOMS

Muscular branches of the ophthalmicartery

Lateral rectus also receives additionalsupply from lacrimal artery

Inferior oblique also receives additional

supply from the infraorbital artery


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Ocular Adnexa

Eyebrows

thickened skin covered with hair

Eyelidsmodified folds of skin

closes to protect the eyeball

blinks to lubricate cornea


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Eyelids


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Eyelids

Skin Layer

Orbicularis Oculi

Areolar tissueTarsal plate

Palpebral conjunctiva


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Orbicularis Muscle


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Lid Margins

Eyelashes

Glands of Zeis

Glands of MollMeibomian glands

lacrimal punctum


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Palpebral Fissure

Elliptical space between the two eyelids

terminates at the lateral and medial canthi


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Orbital septum

Fascia behind the portion of orbicularismuscle and serves as a barrier between

the lid and the orbit


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Eyelids


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Eyelid Anatomy


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Lid retractors

Responsible for opening the eyelids

levator palpebrae superioris muscle

aponeurosismeullers muscle

Lower lid retractor

inferior rectus, extends with the inferior oblique

and insert into the lower border of the tarsal plate


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Upper Eyelids


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Lower Lid Retractors


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Nerve Supply of the Eyelid

First and second division of the trigeminalnerve

Ophthalmiclacrimal, supraorbital,

supratrochlear,infratrochlear, external nasalnerves

Maxillary

Infraorbital, zygomaticofacial,zygomaticotemporal nerves


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Eyelids

Blood Supply

lacrimal and ophthalmic areteries

Venous drainageophthalmic vein

Lymphatic drainage

Temporal eyelids - pre-auricular and parotidnodes

Nasal eyelids - submandibular nodes


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Lacrimal Apparatus

Lacrimal glands

accessory lacrimal glands of Krauss and

WolfringPuncta

Canaliculi

Lacrimal sacNasolacrimal duct


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Lacrimal Apparatus


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Lacrimal Gland

Blood supply - lacrimal artery

Venous drainage - ophthalmic vein

Lymphatic drainage - preauricular lymphnodes

Nerve supply - lacrimal nerve, great

superficial petrosal nerve, sympatheticnerves


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Lacrimal Apparatus


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Optic Nerve

Consists of 1 million axons from ganglioncells of the retina

emerges from the sclera on the nasalportion of the globe

25 - 30mm long in the orbital segment

goes through optic canal10mm intracranial course

joins optic chiasm


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Optic Nerve

Vascular Supply of the


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Optic Nerve


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Visual pathway

Retina

Optic nerve

Optic chiasmOptic tract

Optic radiation

Occipital lobe (Visual center)


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Visual Pathway

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