Anatomy and Anatomy and PhysiologyPhysiologyof the Eyeof the Eye

Dr. Silvestre A. Pascual Jr.Dr. Silvestre A. Pascual Jr.

Department of OphthalmologyDepartment of Ophthalmology

OutlineOutline1.1. THE GLOBETHE GLOBE2.2. THE OUTER COATTHE OUTER COAT

• The CorneaThe Cornea The Corneal EpitheliumThe Corneal Epithelium The Corneal StromaThe Corneal Stroma The Descemet’s MembraneThe Descemet’s Membrane The EndotheliumThe Endothelium

• The ScleraThe Sclera• The Corneoscleral LimbusThe Corneoscleral Limbus

OutlineOutline3.3. THE MIDDLE COATTHE MIDDLE COAT

• The IrisThe Iris• The Ciliary BodyThe Ciliary Body• The ChoroidThe Choroid

4.4. THE INNER COATTHE INNER COAT• The RetinaThe Retina• The PhotoreceptorThe Photoreceptor• The Modulator CellsThe Modulator Cells• The Transmitter CellsThe Transmitter Cells• The Supporting CellsThe Supporting Cells• Regions of the RetinaRegions of the Retina

OutlineOutline

5.5. CHAMBERS OF THE EYECHAMBERS OF THE EYE• Aqueous HumorAqueous Humor• Vitreous HumorVitreous Humor

6.6. LENSLENS

7.7. ZONULESZONULES

THE GLOBETHE GLOBE Occupies the front half Occupies the front half

of the orbitof the orbit

Only the Only the anterior thirdanterior third is exposed consisting is exposed consisting of the of the corneacornea and and sclerasclera

The exposed sclera is The exposed sclera is covered by the covered by the bulbar bulbar conjunctivaconjunctiva

THE GLOBETHE GLOBEHas three main Has three main

layers or coats:layers or coats:o Outer:Outer: cornea, sclera, cornea, sclera,

corneoscleral corneoscleral limbuslimbus

o Middle:Middle: iris, iris, ciliary body, choroidsciliary body, choroids

o Inner:Inner: retinal pigment retinal pigment epithelium and retinaepithelium and retina

THE GLOBETHE GLOBE Has 3 chambers:Has 3 chambers:

o Anterior Chamber Anterior Chamber (w/ (w/ aqueous humor)aqueous humor)

o Posterior Chamber Posterior Chamber (w/ (w/ aqueous humor)aqueous humor)

o Vitreous Chamber Vitreous Chamber (w/ (w/ vitreous humor)vitreous humor)

Contains a Contains a crystalline crystalline lenslens located immediately located immediately behind the irisbehind the iris

THE GLOBETHE GLOBEAP length of 22-26 mm AP length of 22-26 mm (ave.24mm)(ave.24mm)

Circumference 69-81mm Circumference 69-81mm (ave.75mm at the (ave.75mm at the equator)equator)

Volume of the globe = about 6mlVolume of the globe = about 6ml

THE OUTER COATTHE OUTER COATComposed of tough fibrous tissues shaped Composed of tough fibrous tissues shaped

as segments of 2 spheres:as segments of 2 spheres:o Transparent corneaTransparent cornea (anterior 1/6) (anterior 1/6)

o White opaque scleraWhite opaque sclera (posterior 5/6) (posterior 5/6)

The junction of the cornea and sclera known The junction of the cornea and sclera known as the corneoscleral limbus contains the as the corneoscleral limbus contains the Trabecular Meshwork and Canal of SchlemmTrabecular Meshwork and Canal of Schlemm

Focusing light and protecting contents of the Focusing light and protecting contents of the globeglobe

The CorneaThe CorneaHas an average Has an average

radius of curvature of radius of curvature of 7.5mm7.5mm

Functions as the Functions as the MAIN refracting MAIN refracting structure of the eyestructure of the eye

Composed mostly of Composed mostly of collagen fibers collagen fibers (transparent) regular (transparent) regular both in size and both in size and arrangementarrangement

The CorneaThe Cornea It is thinnest at the center (0.5mm) and thickest It is thinnest at the center (0.5mm) and thickest

at the periphery (1.0mm)at the periphery (1.0mm)

The CorneaThe Cornea

Has 5 layers:Has 5 layers:o EpitheliumEpitheliumo Bowman’s layerBowman’s layero StromaStromao Descemet’s Descemet’s

membranemembraneo EndotheliumEndothelium

The Corneal EpitheliumThe Corneal Epithelium

Composed of Composed of stratified squamous stratified squamous epithelium, 5-6 layersepithelium, 5-6 layers

Epithelial cells form Epithelial cells form in the deepest layer, in the deepest layer, become become progressively flatter progressively flatter and are shed 7 days and are shed 7 days laterlater

Basal columnar cells

Wing cells Stratified squamous cells

The Corneal EpitheliumThe Corneal Epithelium

Basement membrane of the basal cells Basement membrane of the basal cells are adherent to the are adherent to the Bowman’s layerBowman’s layer, the , the acellular anterior portion of the stroma, acellular anterior portion of the stroma, resistant to passage foreign bodies or resistant to passage foreign bodies or infective organismsinfective organisms

The Corneal StromaThe Corneal Stroma

Form 90% of the Form 90% of the corneal thicknesscorneal thickness

Contain regularly Contain regularly shaped and sized shaped and sized lamellae of collagen lamellae of collagen fibers secreted by fibers secreted by interspersed interspersed keratocyteskeratocytes

The Descemet’s The Descemet’s MembraneMembrane

The basement membrane of the endothelial The basement membrane of the endothelial cells of the corneacells of the cornea

Terminates abruptly in the periphery of the Terminates abruptly in the periphery of the cornea forming SCHWALBE’S line, the anterior cornea forming SCHWALBE’S line, the anterior border of the Trabecular Meshworkborder of the Trabecular Meshwork

The EndotheliumThe Endothelium

Single layer of Single layer of mesothelium, the mesothelium, the apices of which are in apices of which are in direct contact with direct contact with aqueous humor.aqueous humor.

Responsible for Responsible for deturgesence of the deturgesence of the stromastroma

Does not regenerate Does not regenerate in adult humansin adult humans

The ScleraThe ScleraDense fibrous Dense fibrous

collagenous structure collagenous structure comprising the comprising the posterior 5/6 of the posterior 5/6 of the outer coatouter coat

Is thickest at the region Is thickest at the region surrounding the optic surrounding the optic nerve and thinnest nerve and thinnest immediately posterior immediately posterior to muscle insertionto muscle insertion

The ScleraThe ScleraThe posterior scleral The posterior scleral

foramen through which foramen through which the optic nerve exits is the optic nerve exits is cone shaped and cone shaped and bridged by a sieve like bridged by a sieve like structure, the structure, the lamina lamina cribrosacribrosa

Has three layers: the Has three layers: the episcleraepisclera, , stromastroma, , lamina lamina fuscafusca

The ScleraThe Sclera The The episcleraepisclera is the outermost is the outermost

layer of moderately vascularized layer of moderately vascularized connective tissue. It is attenuated connective tissue. It is attenuated posterior to the equator, making it posterior to the equator, making it relatively avascular relatively avascular

The The scleral stromascleral stroma is composed is composed of collagen fibers irregular in size of collagen fibers irregular in size and arrangementand arrangement

The The lamina fuscalamina fusca is the is the innermost layer made of fine innermost layer made of fine collagen collagen

Which is Cornea? Sclera?Which is Cornea? Sclera?

The Corneoscleral The Corneoscleral LimbusLimbus

Is a transitional zone about 1.5mm in diameterIs a transitional zone about 1.5mm in diameter Inner part of corneoscleral limbus is the Inner part of corneoscleral limbus is the

Trabecular Meshwork which is where aqueous Trabecular Meshwork which is where aqueous humor is drainedhumor is drained

The Corneoscleral The Corneoscleral LimbusLimbus

Also contain the Also contain the Canal of SchlemmCanal of Schlemm, an oval channel , an oval channel line by a single layer of endothelium that drain aqueous line by a single layer of endothelium that drain aqueous humor from Trabecular Meshwork.humor from Trabecular Meshwork.

25-35 collector channels connect with the Canal of 25-35 collector channels connect with the Canal of Schlemm which drain the aqueous humor to the Schlemm which drain the aqueous humor to the anterior ciliaryanterior ciliary and and episcleral veinsepiscleral veins

THE MIDDLE COATTHE MIDDLE COATComposed of the iris, Composed of the iris,

ciliary body and choroidciliary body and choroid IrisIris limits the amount of limits the amount of

light entering the eyelight entering the eyeCiliary bodyCiliary body produces produces

aqueous and the aqueous and the accomodation of the lensaccomodation of the lens

ChoroidChoroid provides the provides the blood supply of the outer blood supply of the outer half of the retinahalf of the retina

The IrisThe IrisThe iris is a diaphragm The iris is a diaphragm

that lies in front of the that lies in front of the lens and ciliary bodylens and ciliary body

The anterior surface is The anterior surface is divided by the divided by the collarettecollarette into a into a central pupillary central pupillary zonezone and a and a peripheral peripheral ciliary zoneciliary zone

Composed of an Composed of an anterior anterior stromastroma and a and a posterior posterior pigmented epitheliumpigmented epithelium

The IrisThe IrisThe The anterior stromaanterior stroma

has 2 layers:has 2 layers:o Anterior borderAnterior border layerlayer

composed of loose composed of loose collagen tissue densely collagen tissue densely packed with pigmented packed with pigmented and nonpigmented cells.and nonpigmented cells.

o Stroma properStroma proper consists consists of bundles of collagen of bundles of collagen fibrils . It has more elastic fibrils . It has more elastic tissues and fewer tissues and fewer pigmented cellspigmented cells

The IrisThe IrisThe The pigmented pigmented

epitheliumepithelium has 2 has 2 layers of cells layers of cells densely packed with densely packed with melaninmelanin::o The The iris sphincter iris sphincter

musclesmuscles and and dilator dilator musclesmuscles are located are located between the iris between the iris pigmented epithelium pigmented epithelium and the stroma properand the stroma proper

The IrisThe IrisBlood supplyBlood supply

- is formed by the 2 long posterior ciliary - is formed by the 2 long posterior ciliary arteries and 7 anterior ciliary arteriesarteries and 7 anterior ciliary arteries

- at the iris root is found the major arterial - at the iris root is found the major arterial circle of the iriscircle of the iris

- radial arteries travel the iris and form the - radial arteries travel the iris and form the minor arterial circle at the area of the collaretteminor arterial circle at the area of the collarette

The Ciliary BodyThe Ciliary Body Is a ring of tissue about Is a ring of tissue about

6mm wide located 6mm wide located posterior to the iris rootposterior to the iris root

Has 2 parts:Has 2 parts:o The The uveal portionuveal portion

-is composed of 3 -is composed of 3 layers of smooth muscles: layers of smooth muscles: longitudinallongitudinal, , radialradial and and circularcircular

-function is mostly -function is mostly for accommodationfor accommodation

The Ciliary BodyThe Ciliary Bodyo The The epithelial portionepithelial portion

-is divided into:-is divided into:

• pars plicatapars plicata - forms the anterior - forms the anterior 2mm and consists of 60-70 folds 2mm and consists of 60-70 folds on ciliary processes. Each ciliary on ciliary processes. Each ciliary process is made of an outer process is made of an outer nonpigmented epithelium and an nonpigmented epithelium and an inner pigmented epithelium. inner pigmented epithelium. Secretion of aqueous humor is Secretion of aqueous humor is the main function of the the main function of the nonpigmented epithelium.nonpigmented epithelium.

• pars planapars plana - forms the posterior - forms the posterior 4mm of the epithelial portion4mm of the epithelial portion

The ChoroidThe Choroid Is the vascular sheet that Is the vascular sheet that

provides the blood supply of provides the blood supply of the retinal pigment epithelium the retinal pigment epithelium and outer half of the retinaand outer half of the retina

Extends from ora serrata to Extends from ora serrata to the optic nervethe optic nerve

Composed of 3 layers of Composed of 3 layers of blood vessels: the blood vessels: the outer outer vascular layer of Hallervascular layer of Haller, , middle vascular layer of middle vascular layer of SattlerSattler and and ChoriocapillarisChoriocapillaris

They are bounded by fibrous They are bounded by fibrous tissues: the tissues: the Lamina FuscaLamina Fusca and and Bruch’s membraneBruch’s membrane

THE INNER COATTHE INNER COAT The RetinaThe RetinaReceptor and Receptor and

Processor of imagesProcessor of images Innermost film that Innermost film that

receives, modulates receives, modulates and transmits light and transmits light impulses to form impulses to form imagesimages

The RetinaThe Retina Its anterior border is the Its anterior border is the ora serrataora serrata and and

extends posteriorly up to the extends posteriorly up to the optic nerveoptic nerveComposed of the Composed of the retinal pigment epitheliumretinal pigment epithelium

and the and the sensory retinasensory retina

The RetinaThe RetinaThe The retinal pigment retinal pigment

epitheliumepithelium is a is a single layer of single layer of hexagonal cells rich hexagonal cells rich in melanin pigment in melanin pigment which functions to which functions to trap light trap light

The RetinaThe RetinaThe The sensory retinasensory retina

is made of layers of is made of layers of cells composed of cells composed of receptor neurons and receptor neurons and glial cells to receive, glial cells to receive, modulate and modulate and transmit images to transmit images to the brainthe brain

The The Photoreceptors: Photoreceptors: Rods & ConesRods & ConesSpecialized Specialized

receptors which receptors which receives imagesreceives images

2 cell types: 2 cell types: rodsrods for for dark vision and dark vision and conescones for light vision for light vision as well as color as well as color visionvision

Macular lutea (only Macular lutea (only cones are found) – cones are found) – temporal to the optic temporal to the optic discdisc

The Modulator CellsThe Modulator CellsLight received by Light received by

photoreceptors are photoreceptors are then processed by then processed by modulator cellsmodulator cells

3 types of cells: 3 types of cells: bipolarbipolar, , horizontal horizontal and and amacrineamacrine cells cells

The Modulator CellsThe Modulator CellsBipolar cellBipolar cell dendrites dendrites

attach to attach to photoreceptors and photoreceptors and the axons synapse the axons synapse with ganglion cellswith ganglion cells

The Modulator CellsThe Modulator CellsHorizontal cellHorizontal cell dendrites attach to dendrites attach to

several adjacent photoreceptors several adjacent photoreceptors and the axons synapse with and the axons synapse with several photoreceptors in a several photoreceptors in a distant part of the retina and distant part of the retina and some to bipolar cells. Horizontal some to bipolar cells. Horizontal cells act as condensers collecting cells act as condensers collecting impulses from groups of impulses from groups of photoreceptors, photoreceptors, integrate and integrate and triggertrigger a visual impulse a visual impulse

The Modulator CellsThe Modulator CellsAmacrine cellsAmacrine cells processes processes

are oriented in the opposite are oriented in the opposite direction in terms of light direction in terms of light transmission. Their transmission. Their processes attach to groups processes attach to groups of ganglion cells and of ganglion cells and bipolar cells. They are bipolar cells. They are believed to believed to inhibit inhibit integrationintegration of visual impulse of visual impulse

The Transmitter The Transmitter Cells:Cells:Ganglion CellsGanglion Cells Transmit the visual Transmit the visual

impulses from bipolar and impulses from bipolar and amacrine cells to the amacrine cells to the midbrainmidbrain

Physiologically, they Physiologically, they transmit either visual transmit either visual impulses to the midbrain impulses to the midbrain (LGB) or afferent impulses (LGB) or afferent impulses of the light reflex (IC)of the light reflex (IC)

Axons of the ganglion cells Axons of the ganglion cells form the form the nerve fiber layernerve fiber layer

The Transmitter The Transmitter Cells:Cells:Ganglion CellsGanglion Cells The nerve fibers from the The nerve fibers from the

ganglion cells converge to ganglion cells converge to exit the eye through the exit the eye through the lamina cribrosa as the optic lamina cribrosa as the optic nervenerve

Intraocularly, it is viewed as Intraocularly, it is viewed as the vertically oval shaped the vertically oval shaped optic discoptic disc

At the center of the disc is a At the center of the disc is a depression known as the depression known as the optic cupoptic cup

The Supporting Cells:The Supporting Cells:Müller CellsMüller CellsMüller cells are large Müller cells are large

astrocytes that astrocytes that mechanically support mechanically support the retinathe retina

Also known as retinal Also known as retinal “nurse cells” as they are “nurse cells” as they are believed to provide the believed to provide the retina enzymes used for retina enzymes used for glycolysisglycolysis

Regions of the RetinaRegions of the Retina Ora serrataOra serrata Central retina (macular Central retina (macular

lutea)lutea) Fovea centralisFovea centralis Peripheral retinaPeripheral retina

CHAMBERS OF THE CHAMBERS OF THE EYEEYE Anterior chamber Anterior chamber

–aqueous humor–aqueous humor

Posterior chamber Posterior chamber –aqueous humor–aqueous humor

Vitreous chamber Vitreous chamber – vitreous humor– vitreous humor

Aqueous HumorAqueous HumorFluid that fills the anterior Fluid that fills the anterior

and posterior chamberand posterior chamberProvides nutrients to the Provides nutrients to the

avascular tissuesavascular tissuesSecreted by the Secreted by the

nonpigmented epithelium nonpigmented epithelium of the ciliary body and of the ciliary body and drained through the drained through the Trabecular meshworkTrabecular meshwork

Volume is about 0.2mLVolume is about 0.2mL

Vitreous HumorVitreous HumorFills the vitreous cavityFills the vitreous cavityAttached firmly to the Attached firmly to the

periphery at the ora serrata periphery at the ora serrata and posteriorly to the rim of and posteriorly to the rim of the optic nerve and the the optic nerve and the central retinacentral retina

Mainly composed of salts, Mainly composed of salts, protein, hyaluronic acid and protein, hyaluronic acid and 98% water98% water

Act as a refracting medium Act as a refracting medium and a volume filler of the eyeand a volume filler of the eye

LENSLENSCrystalline lens is a Crystalline lens is a

grossly transparent, grossly transparent, biconvex tissuebiconvex tissue

More curved posteriorly More curved posteriorly (radius of curvature of (radius of curvature of about 6mm) than about 6mm) than anteriorlyanteriorly

Refracting surface with a Refracting surface with a refracting power of about refracting power of about 1/2 of the cornea1/2 of the cornea

LENSLENSComposed of: lens Composed of: lens

capsule, cells or lens capsule, cells or lens fibers with their nuclei at fibers with their nuclei at the lens equator and the lens equator and those with their nuclei those with their nuclei under the anterior under the anterior capsule, lens cortex, and capsule, lens cortex, and lens nucleuslens nucleus

Held in place by zonules Held in place by zonules of Zinnof Zinn

LENSLENSLens capsuleLens capsule – envelopes the entire lens; – envelopes the entire lens;

composed of thick anterior capsule & thin composed of thick anterior capsule & thin posterior capsuleposterior capsule

Lens nucleusLens nucleus – innermost, central region – innermost, central region composed of lens fibers that are no longer composed of lens fibers that are no longer attached to the posterior capsuleattached to the posterior capsule

Lens cortexLens cortex – composed of lens fibers that – composed of lens fibers that have lost their nuclei near the equator of the have lost their nuclei near the equator of the lens & their posterior processes attached to the lens & their posterior processes attached to the posterior capsuleposterior capsule

ZONULESZONULESSuspensory ligament Suspensory ligament

of the lensof the lensSupports the lens in Supports the lens in

position and position and connects the lens to connects the lens to the ciliary musclethe ciliary muscle

Composed of fine Composed of fine fibrils of modified fibrils of modified collagenous tissuecollagenous tissue

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