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Eye
Layers
• Cornealscleral layer (tunica fibrosa)
• Uvea (tunica vasculosa)
• Retinal layer (tunica interna or nervosa)
Cornea Sclera
Sheathsof nerve
IrisCiliarybody
Ciliaryprocesses
Choroid
Neuralretina
Non-nervousanterior portion
Retinalpigment epithelium
Supporting coat Vascular coat Retinal coat
Refractive media
• Cornea• Lens• Suspensory ligament (Zonule)• Aqueous humor• Vitreous body
Chambers/body
• Anterior chamber
• Posterior chamber
• Vitreous chamber
Accessory structures
• Eyelid
• Lacrimal apparatus
• Extrinsic eye muscles
Cornea
Anterior chamber
Lens
Schlemm’s canal
Ciliary muscle
Limbus
Ora serrata
Zonule
Posteriorchamber
Iris
Ciliary bodyand process
Vitreous body
Photosensitiveretina
Choroid
Sclera
Fovea
Opticpapilla
Sclera
Pigment epitheliumChoroid
Optic nerve
1
23 4
Cornealscleral layer
• Cornea (anterior 1/6 of eye)– Epithelium– Bowman’s membrane– Substantia propria– Descemet’s membrane– Endothelium
Corneal epithelium
Bowman’s membrane
Substantia propria
Descemet’smembrane
Corneal endothelium
Cornealscleral layer
• Sclera (posterior 5/6 of eye)– Dense fibrous connective tissue with
elastic and collagenous fibers– Tendons of extrinisic eye muscles
insert into this layer– Optic nerve region: sieve-like
• Forms lamina cribrosa
Scleral sulcus
CorneaPosterior chamberAnterior
chamber
Lens
Sclera
Vitreous body
Laminacribrosa
Limbus
• Corneo-scleral junction– Corneal epithelium continuous with
bulbar conjunctiva– Blood vessels that supply cornea– Endothelium
• Spaces of Fontana: the trabecular meshwork
• Canal of Schlemm: circumferential vessel that drains aqueous humor into episcleral veins (in limbus)
Limbal conjunctiva
Limbal stroma
Canal of Schlemm
Cornea
Posterior chamber
Anterior chamber
Trabecularmeshwork
Iris
Uvea
• Middle, highly vascular layer• Three components:
– Choroid– Ciliary body
• Ciliary processes• Ciliary muscle
– Iris
IrisCiliary body
Zonule
Choroid
Choroid
• Loose connective tissue
• Richly vascularized
• Pigmented
• Several layers
Ciliary Body
• Girdles eye anterior to ora serrata• Triangular in shape in section• Two components:
– Ciliary processes– Ciliary muscle
Cornea
Sclera
Lens
Corneal epithelium
Canal of Schlemm
Bulbar conjunctiva
Ciliary muscle
Oraserrata
Ciliary process
Vitreous
Hyaloideo-capsular ligament
Nuclear zone oflens
SphincterOf pupil
Dilatorof pupil
Iris
Anterior chamber
Posterior chamber
Cornea
Canal of Schlemm
Conjunctiva
Ciliary muscle
Sclera
Episcleraltissue
Episcleralvessels
IrisSphincter pupillae
Ora serrata
Hyaloidea
Lens
Zonula ciliaris
Ciliaryprocess
Ciliary processes
• Form the aqueous humor• Ciliary epithelium
– Two layers• Deep, pigmented layer• Superficial non-pigmented layer (represents a
non-nervous extension of the nervous portion of the retina anterior to the ora serrata)
• Stromal cores with numerous capillaries
Zonular fiber
Epithelium
Pigment layer
Vessel layer
Ciliary muscle
Anterior chamber
Posterior chamber
Aqueous pathway
Vitreous cavity
Iridocorneal angle
Bulbarconjunctiva
Canal of Schlemm
Anterior corneal epithelium
Substantia propriaIrisCornea Sphincter pupillae
Anteriorlensepithelium
Posterior irisepithelium
Lens fibers
Lens capsule
Zonulaciliaris Equator
of thelens
Ciliaryprocesses
Ciliarymuscle
Ciliary muscle
• Smooth muscle• Three sets of muscle fibers with
different orientations• Important in accommodation
– Contraction: releases tension on lens– Relaxation: increases tension on lens
• Parasympathetic innervation
Cornea
Sclera
Lens
Ciliary muscle
Sphincterof pupil
Anterior chamber
Posterior chamber
Dilatorof pupil
Ciliary processes
Zonule
Ora serrata
Cornea
Ciliarymuscle,relaxed
Suspensoryligament
pulls (arrow)to flatten lens
Zonula fibers(= suspensory ligament)relaxed
Lens, relaxed and permitted toassume greater curvature byits own elasticity (arrow) andpulled forward by themeridional fibers
Aqueous humorMeridional fibersCircular fibers of ciliary muscle, contracted
Iris
• Anterior portion– Endothelial surface– Underlying connective tissue
• Many pigmented cells: chromatophores• Amount of pigment determines eye color
– blue eyes: little or no pigment– Gray, green, and brown eyes: increasing
pigment
– Smooth muscle• Sphincter: parasympathetic innervation• Dilator: sympathetic innervation
Iris
• Posterior portion– Heavily pigmented in all individuals– Two rows of cuboidal cells
Sphincter papillae muscle Stroma of the iris
Pigment epithelium
Melanocytes
Retina
• Inner layer of eye; sensitive portion continues anteriorly only to ora serrata
• Anterior to ora serrata continues as the non-nervous pars ciliaris
• Ten named layers
Ora serrata
Pars opticaof the retina
Foveacentralis
Maculalutea
• Pigment epithelium• Rods and cones layer• External (outer) limiting membrane• Outer nuclear layer• Outer plexiform layer• Inner nuclear layer• Inner plexiform layer• Ganglion cell layer• Nerve fiber layer• Internal (inner) limiting layer
Pigment epithelium
Layer of rods and cones
External limiting membrane
Outer nuclear layer
Outer plexiform layer
Inner nuclear layer
Inner plexiform layer
Ganglion cell layer
Optic nerve fiber layer
Internal limiting membrane
Pigmented epithelium
Rod photoreceptor
Outer limiting membrane
Cone photoreceptor
Cone cell nucleiRod cell nucleus
Cone pedicleRod spherule
Horizontal cellBipolar cell
MÜller cell nucleus
Body of MÜller cell
Amacrine cell
Ganglion cells
Optic nerve fibers
Light
Inner limiting membrane
Rod
Cone
Bipolar neurons
Pigmented epithelium
Ganglion neuron
Optic nerve fibers to brain
Müllercell
Nucleiof ganglioncells
Nucleiof bipolarneurons
Nucleiof rods andcones
Direction of Light from Lens
ILMONFL
GCL
IPL
INL
OPL
ONL
R&CL
OLM
PE
Artery
Outer nuclear layer
Cones and rods
Choroid
Sclera
Inner nuclear layer
Ganglion cell layer
Nerve fiber layerInner plexiformlayer
Outer plexiformlayer
Pigmentepithelium
Venule
Arteriole
Melanocytes
Synthesis of melaninby RER, Golgi, andmelanosomes. Melaninabsorbs light after ithas sensitized thereceptor.
Ion transport by mito-chondria and membraneinvaginations.
Digestion, by lysosomalenzymes, of photo-receptor fragementsphagocytized bypigment epithelial cells.
Vitamin A transportand esterificationin SER.
Major retinal cell types
• Photoreceptor cells– Rod cells– Cone cells
• Bipolar cells
• Ganglion cells
Other cell types
• Horizontal cells
• Amacrine cells
• MÜller cells
Rod cells
• 130 million• Intensity discrimination; night
vision• Outer segment: rhodopsin
– Rod-shaped; membranous stacks of disks contain pigment
• Inner segment: organelles• Nuclear and synaptic regions• 100 rods supply each ganglion cell
Synaptic body
Nucleus
Inner segment
Outer segment
Connecting structure (cilium)
m
e
Cone cells
• 6-7 million• Color perception and visual acuity• Outer segment: iodopsins
– Conically shaped; membranous stacks of disks contain pigment
• Inner segment: organelles• Nuclear and synaptic regions• 1-10 cones supply each ganglion
cell
Inner segment
MitochondriaCilium
Outer segment
Cone cell
Outer segments
CiliumMitochondria
Inner segment
Cone
Rod
Cilium
Basalbody
Rootlet
Rod Cell Cone Cell
Free-floatingdisks
Bipolar cells
• Extend from outer to inner plexiform layers
• Cell bodies lie in inner nuclear layer
Outernuclearlayer
Outer plexi-form layer
Innernuclearlayer
Inner plexi-form layer
Ganglioncell layer
ConeCone
Rod
Horizontal cellBipolarcell
Lateral pathway
Bipolarcell
AmacrinecellAmacrine
cell
Ganglioncell
To optic nerve
Verticalpathway
Light
Ganglion cells
• Give rise to optic nerve
• Processes form nerve fiber layer
• Cell bodies lie in ganglion cell layer
Outernuclearlayer
Outer plexi-form layer
Innernuclearlayer
Inner plexi-form layer
Ganglioncell layer
ConeCone
Rod
Horizontal cellBipolarcell
Lateral pathway
Bipolarcell
AmacrinecellAmacrine
cell
Ganglioncell
To optic nerve
Verticalpathway
Light
Other retinal cell types
• Horizontal cells– Connect groups of cone cells in one area
with rods and cones in another area– Probably integrate information between
rods and cone
• Amacrine cells– Primarily associated with ganglion cells– Function: ??
Outernuclearlayer
Outer plexi-form layer
Innernuclearlayer
Inner plexi-form layer
Ganglioncell layer
ConeCone
Rod
Horizontal cellBipolarcell
Lateral pathway
Bipolarcell
AmacrinecellAmacrine
cell
Ganglioncell
To optic nerve
Verticalpathway
Light
Other retinal cell types
• MÜller cells
– Retinal glial cells
– Very large: stretch from internal to external limiting membranes
– Supportive function
Pigmented epithelium
Rod photoreceptor
Outer limiting membrane
Cone photoreceptor
Cone cell nucleiRod cell nucleus
Cone pedicleRod spherule
Horizontal cellBipolar cell
MÜller cell nucleus
Body of MÜller cell
Amacrine cell
Ganglion cells
Optic nerve fibers
Light
Inner limiting membrane
Retinal modifications
• Macula lutea– Lies in direct optic axis– ~ 5 mm in diameter– Rods gradually disappear– Cones become increasingly slender
and numerous– Fovea centralis: entirely cones
• ~ 0.6 mm in diameter• Clearest vision and greatest visual acuity
NFL
GCL
IPL
INL
OPL
ONL
R&C
Pigment epitheliumCone cells
Ganglion cells
Fovea centralis
ILM
OLM
Normalright eye fundus
Retinal modifications
• Ora serrata
– Anterior scalloped margin of nervous portion of retina
Sclera
Ora serrata
Choroid
Epithelium
Ciliary extensionof retina
Retina with nerve elements
x150
Retinal modifications
• Optic disc– Forms the blind spot of the retina– Represents the retinal aspect of the
optic nerve– Optic papilla: portion of disc that is
slightly raised due to a heaping up of nerve fibers
– Physiological cup: small central depression from which central artery and vein of retina emerge
Central indentation of optic disc
Centralartery
Ciliary arteries andnerves
DuraArachnoidOptic nerve
Retina
Laminacribrosa
Refractive media
• Cornea• Lens• Zonule (suspensory ligament)• Aqueous humor• Vitreous body
Lens
• Capsule (a basal lamina; Type IV collagen)– Homogeneous; zonular fibers attach to it
• Subcapsular epithelium– Single layer of cells on anterior surface– Transformed into lens fibers at equator
Lens
• Lens substance– Lens fibers (cells)– Older ones near center– Younger ones more peripheral
• Aging of lens– Gradually loses water: becomes less
elastic– Result is inability of lens to accommodate
Anterior pole
Anterior epithelium
Newly formedsecondary lens fibers
Nuclei of lensfibers forming“nuclear bow”
Equator
Posterior pole
Capsule
Equatorialepithelium
Primary lens fibers
Zonule
• Numerous fine fibers
– Stretch from ciliary body to equator of lens
– Thin collagen fibers and fibrillin
Aqueous humor
• Thin watery substance
• Produced by ciliary processes
Vitreous body
• Clear, transparent gel; 99% water
• Fills space posterior to lens
• Contains collagen-like proteins plus hyaluronic acid
Accessory structures
• Eyelids
• Lacrimal gland
Eyelid
• Tarsal plates: dense c.t.; support and strength to eyelid
• Skeletal muscle: raises eyelid• Thin skin covers outer surface• Conjunctiva: a mucous membrane
– Palpebral: 2 cell layers with goblet cells– Bulbar: continuous at limbus with
corneal– epithelium
Eyelid
• Glands– Sebaceous glands
• Meibomian– embedded in tarsal plates; inflammation
produces a sty– Lubricate edges of lids
• Zeis– Associated with hair follicles
– Sweat glands (glands of Moll)
• Eyelashes: 2-3 rows
Skin
Orbicularis muscle
Eyelashes
Conjunctiva
Tarsal plate
Meibomian glands
Lacrimal gland
• Compound tubuloalveolar gland
• Serous secreting
• Many myoepithelial cells
Eye
Eye
Integument
Serous tarsal gland
Tarsus
Orbicularis oculi muscle
Conjunctiva
Sebaceous tarsal gland (of Meibom)
Eyelashes
Sebaceous and sweat glands
Marginal fascicle of orbicularis oculi muscle
sclera
posteriorpole
anteriorpole
cornea
choroid
iris
ciliarybody
retina
lensopticnervepigment
epithelium
Eye terminology
• Poles– Anterior: central point of corneal curvature– Posterior: central point of scleral curvature
• Geometrical axis: anterior to posterior poles
• Visual axis: center of pupil to fovea• Anatomical equator• Meridians: vertical and horizontal
Anterior chamberIris
Lens
Ciliarybody
Vitreous
Fovea
Laminacribrosa
Zonulaciliaris
Ora serrata
Dura
Optic nerve P.P.
V.A.
A.P.Posterior chamber
Limbus
Ciliary muscle
Lateral rectus
Sclera
ChoroidRetina
Cornea
Conjunctiva
Canal of Schlemm
Medial rectus
Visual axis Optical (geometrical) axis
Pars iridicaPars ciliaris
Ora serrata
Pars opticaof the retina
Foveacentralis
Maculalutea
Nervefiberlayer
Ganglion cell layer
Internal plexiform layer
Internal nuclear layer
External plexiform layer
External nuclear layer
Photoreceptor layerConeRod
Pigment epithelium
Dir
ect
ion o
f lig
ht
Outer segment
Cilium
Inner segment
Outer rod fiber
Cell body
Inner rod fiber
Rod spherule