ANATOMY AND PHYSIOLOGY OF THE EYE

Department of OphthalmologyFatima College of Medicine

ORBIT

BONY CAVITY WHICH HOUSES THE EYEBALL

4 WALLS - ROOF,FLOOR, MEDIAL AND LATERAL WALL

30 mL in volumeHAS AN APEX WHERE NERVES AND

VESSELS EMERGE

Orbital Walls

ORBITAL WALLS

ROOF COMPOSED OF THE LESSER WING OF

THE SPHENOID, AND ORBITAL PLATE OF THE FRONTAL BONE

INTIMATELY RELATED TO THE FRONTAL SINUS

ORBITAL WALLS

LATERAL WALL SEPARATED FROM THE ROOF BY THE

SUPERIOR ORBITAL FISSURE COMPOSED OF THE GREATER WING OF

THE SPHENOID, ZYGOMATIC BONE STRONGEST PART OF THE BONY ORBIT

ORBITAL WALLS

FLOOR SEPARATED FROM THE LATERAL WALL BY

THE INFERIOR ORBITAL FISSURE INTIMATELY RELATED TO THE MAXILLARY

SINUS COMPOSED OF MAXILLARY BONE,

ZYGOMATIC BONE AND PALATINE BONE ORBITAL CONTENTS CAN HERNIATE INTO

THE MAXILLARY SINUS IN TRAUMA CASES

ORBITAL WALLS

MEDIAL WALL INTIMATELY RELATED TO THE ETHMOID

AND SPHENOID SINUSES COMPOSED OF THE ETHMOID BONE,

SPHENOID BONE, LACRIMAL BONE AND MAXILLA

ORBITAL APEX

SERVES AS A PORTAL FOR NERVES AND VESSELS

SITE OF ORIGIN OF ALL EOMS EXCEPT INFERIOR OBLIQUE

Orbital Apex

SUPERIOR ORBITAL FISSURE

LATERAL PORTION SUPERIOR OPHTHALMIC VEIN LACRIMAL NERVE FRONTAL NERVE TROCHLEAR NERVE

MEDIAL PORTION SUPERIOR AND INFERIOR DIV. OF

OCULOMOTOR NERVE

ORBITAL APEX

OPTIC CANAL TRANSMITS OPTIC NERVE AND

OPHTHALMIC ARTERYSUPERIOR ORBITAL FISSURE

ALSO TRANSMITS THE INFERIOR OPHTHALMIC VEIN

BLOOD SUPPLY OF THE ORBIT

OPHTHALMIC ARTERY CENTRAL RETINAL ARTERY LACRIMAL ARTERY MUSCULAR BRANCHES LONG AND SHORT POSTERIOR CILIARY

ARTERY MEDIAL PALPEBRAL ARTERIES

Blood Supply of the Eyeball

BLOOD SUPPLY

SHORT POSTERIOR CILIARY ARTERY CHOROID, OPTIC NERVE

LONG POSTERIOR CILIARY ARTERY SUPPLY CILIARY BODY, ANASTOMOSE

WITH EACH OTHER AND ANTERIOR CILIARY ARTERY TO FORM THE MAJOR ARTERIAL CIRCLE

BLOOD SUPPLY

Anterior ciliary artery derived from muscular branches of the

rectus muscles anterior sclera, episclera, limbus,

conjunctiva

Venous Drainage of the Orbit

Superior and Inferior Ophthalmic Veins

Vortex veinsAnterior Ciliary VeinsCentral retinal Veins

Venous Drainage of the Eyeball

Venous DrainageThe ophthalmic veins communicate with

the cavernous sinus via SOF and the pterygoid 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

Eyeball

Roughly sphericalapproximately 24.5 mm (less than

an inch) in lengthabout 5mL in total volume

Eyeball

Histological Cross Sectionof the Eyeball

Conjunctiva

Thin transparent mucous membrane which covers the posterior surface of the eyelid (palpebral conjunctiva) and the anterior surface of the sclera (bulbar conjunctiva)

composed of two to five layers of stratified columnar epithelial cells

contains glands which help in ocular lubrication

Conjunctiva

Blood Supply anterior ciliary artery palpebral aretries

Nerve Supply first division of the trigeminal nerve

Upper Eyelids

Lower Lid Retractors

Tenon’s Capsule

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

continuous with the EOM’sthickens to form check ligaments

Sclera

Fibrous outer protective coating of the eye

composed of dense bands of well hydrated connective tissue

Episclera

Fine elastic tissue containing blood vessels and covers the anterior surface of the sclera

CorneaTransparent tissue which accounts for

most of the refractive power of the eyethicker at the limbus, and thinner at the

center5 layers

epithelium Bowman’s layer Corneal stroma Descemet’s layer Endothelium

Cornea

Cornea

Uveal Tract

IrisCiliary BodyChoroid

Posterior View of Uveal Tissue

Iris

Flat anterior extension of the ciliary body

has a central round aparture known as the pupil

divides the anterior from the posterior chamber

Iris

Ciliary Body

Extends from the choroid to the irisdivided into the pars plicata and pars

planapoint of suspension of the lens produces aqueous humor

Aqueous Flow

Choroid

Posterior segment of the uveal tract in between the retina and sclera

joins the ciliary body anteriorlychoroidal blood vessels nourish outer

portion of the retina

Ora Serrata

Choroidal Circulation

Lens

Biconvex, avascular, colorless and transparent structure

second most powerful refractive tissue

held in place by suspensory ligaments known as zonules

accommodates to facilitate near vision

Lens Accommodation

Lens in the Young

Lens in the Aged

Anterior Chamber Angle

Schwalbe’s lineSchlem’s canalTrabecular meshworkScleral spur

Anterior Chamber Angle

Trabecular Meshwork

Aqueous Flow

Optic Nerve Cupping

Retina

Thin, semitransparent, multilayered sheet of neural tissue

lines the inner aspect of the posterior two thirds of the globe

terminates anteriorly as the ora serrata

Fundus

Posterior Pole

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

Retinal Layers

Macula

Center of the posterior retinaresponsible for fine central visionhas yellow pigment (xantophyll)histologically empty space tends to

the accumulation of extracellular material that cause thickening

Photoreceptors

Blood Supply of the Retina

Choriocapillaries outer third of the retina

Central Retinal Artery inner two thirds of the retina

Embryonic Eye

Embryonic Eye

Vitreous

Clear, avascular, gelatinous bodycomprises 2/3 of the volume of the

eye99% water ; 1% hyaluronic acid and

collagenfirmly attached to the pars plana and

ora serrata

Eyeball

External Anatomic Landmarks

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

Ora Serrata - 6mm from the limbus on the nasal side ; 7mm from the limbus on the temporal side

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

limbus

Extraocular Muscles

Rectus Muscles superior rectus inferior rectus medial rectus lateral rectus

Oblique Muscles Superior oblique Inferior oblique

Extraocular Muscles

Nerve Supply of EOMS

Oculomotor nerve innervates medial, inferior and superior rectus muscles as well as the inferior oblique muscle

Abducens nerve innervates the lateral rectus muscles

Trochlear nerve innervates the superior oblique muscle

Blood Supply of the EOMS

Muscular branches of the ophthalmic artery

Lateral rectus also receives additional supply from lacrimal artery

Inferior oblique also receives additional supply from the infraorbital artery

Ocular Adnexa

Eyebrows thickened skin covered with hair

Eyelids modified folds of skin closes to protect the eyeball blinks to lubricate cornea

Eyelids

Eyelids

Skin LayerOrbicularis OculiAreolar tissueTarsal platePalpebral conjunctiva

Orbicularis Muscle

Lid Margins

EyelashesGlands of ZeisGlands of MollMeibomian glandslacrimal punctum

Palpebral Fissure

Elliptical space between the two eyelids

terminates at the lateral and medial canthi

Orbital septum

Fascia behind the portion of orbicularis muscle and serves as a barrier between the lid and the orbit

Eyelids

Eyelid Anatomy

Lid retractors

Responsible for opening the eyelids levator palpebrae superioris muscle

aponeurosismeuller’s muscle

Lower lid retractorinferior rectus, extends with the inferior

oblique and insert into the lower border of the tarsal plate

Upper Eyelids

Lower Lid Retractors

Nerve Supply of the Eyelid

First and second division of the trigeminal nerve

Ophthalmic lacrimal, supraorbital,

supratrochlear,infratrochlear, external nasal nerves

Maxillary Infraorbital, zygomaticofacial,

zygomaticotemporal nerves

Eyelids

Blood Supply lacrimal and ophthalmic areteries

Venous drainage ophthalmic vein

Lymphatic drainage Temporal eyelids - pre-auricular and

parotid nodes Nasal eyelids - submandibular nodes

Lacrimal Apparatus

Lacrimal glandsaccessory lacrimal glands of Krauss

and WolfringPunctaCanaliculiLacrimal sacNasolacrimal duct

Lacrimal Apparatus

Lacrimal Gland

Blood supply - lacrimal arteryVenous drainage - ophthalmic veinLymphatic drainage - preauricular

lymph nodesNerve supply - lacrimal nerve, great

superficial petrosal nerve, sympathetic nerves

Lacrimal Apparatus

Optic Nerve

Consists of 1 million axons from ganglion cells of the retina

emerges from the sclera on the nasal portion of the globe

25 - 30mm long in the orbital segmentgoes through optic canal10mm intracranial coursejoins optic chiasm

Optic Nerve

Vascular Supply of the Optic Nerve

Visual pathway

RetinaOptic nerveOptic chiasmOptic tractOptic radiationOccipital lobe (Visual center)

Visual Pathway