lecture1 anatomy of the eye
TRANSCRIPT
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