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THE EYEBALL
Prof. Dr. Selda Önderoğlu
Department of Anatomy
THE ORGAN OF VISION
• Located in the orbit- embedded in
orbital fat
• Fascial sheath- capsule of Tenon
• Two spheres
- anterior segment
--transparent , 1/6
- posterior segment
-- opaque, 5/6
AXES OF EYEBALL
OCULAR AXIS
- anterior poleposterior pole
- parallel in two eyeballs
OPTIC AXIS
- posterior pole of lensfovea centralis
- Not parallel in two
eyeballs
EQUATOR OF EYEBALL
LAYERS (TUNICS)
1-FIBROUS LAYER
2-VASCULAR LAYER
(uveal tract)
3-NERVOUS LAYER
(retina)
FIBROUS LAYER- FUNCTIONS
• A place for the
attachment of
muscles.
• Maintain a constant
intraocular
pressure.
• Protect the deeply
located structures.
FIBROUS LAYER
• SCLERA ( characteristics )
-5/6 POSTERIOR PART
White part
Opaque, hard
Thickest behind
. CORNEA
-1/6 ANTERIOR PART
Transparent
SCLERA
• Tenon’s capsule
(Fascial Sheath-Vagina Bulbi)
• Episcleral space
• SCLERA
• Perichoroidal spacedelicate cellular tiss.
. VASCULAR LAYER
SCLERA
IS POSTERIORLY
PIERCED BY:
fibers of the optic
nerve(LAMINA CRIBROSA
SCLERAE)
ciliary vessels and nerves
central vessels of retina
venae vorticosae
( 4-5 in number)
SCLERA
meets the CORNEA at the
• SCLEROCORNEAL JUNCTION
( LIMBUS CORNEA )
• SINUS VENOSUS SCLERAE
( SCHLEMM’S CANAL )
-At the sclerocorneal junction.
SCLERA
Vessels ----- few.
Nerves-------ciliary nerves
CORNEA
• The major site of
refraction of light
entering the eye.
• 1/6 anterior part More
convex.
• Transparent.
• Avascular.
• Rich in nerves-opthalmic
n.
• Does not have lymph
vessels.
VASCULAR LAYER
(UVEAL TRACT )
• CHOROID
• CILIARY
BODY
• IRIS
CHOROID
• 5/6 posterior part of the
eyeball.
• highly vascular
• Color– dark brown
• Extends as far as the ora
serrata.
• Outer surface is related
to—suprachoroid lamina
• Inner surface—pigmented
layer of retina
CILIARY BODY
CHOROID
continues
anteriorly
as the
ciliary body
CILIARY BODY
• Rich in blood supply
• CILIARY PROCESSES
secrete
AQUEOUS HUMOUR
• SUSPENSORY
LIGAMENTStowards the lens
CILIARY BODY-FUNCTIONS
• SUSPENSION OF LENS
• PRODUCTION OF
AQUEOUS HUMOUR
• CHANGING THE
ANTERO-POSTERIOR
DISTANCE OF LENS
(FOR THE MECHANISM
OF ACCOMODATION )
CILIARY MUSCLE
• Smooth muscle• Nerve-psympOCULOMOTORpostganglionic fibers from
ciliary ganglion
• Function-changes in
anteroposterior distance of
lens.
---contract-susp. Lig.
Relax.-thickness of lens
increases. (or opposite)
IRIS
• Coloured (blue- dark
brown )
• Surrounds the pupil
• Adjustable diaphragm
• Has two margins
- CILIARY
- PUPILLARY
IRIS
• Somewhat suspended in
aqueous humour and divides
the area between cornea
and lens into two chambers
• ---ANTERIOR
---POSTERIOR
Cornea – iris meet at
—IRIDOCORNEAL ANGLE.
AQUEOUS HUMOUR
CILIARY PROCESSES -> POSTERIOR CHAMBER - >
PUPIL –> ANTERIOR CHAMBER –> SINUS VENOSUS
SCLERAE (at the iridocorneal angle) –> ANTERIOR
CILIARY VEINS- > OPHTHALMIC VEINS –>
CAVERNOUS SINUS
MUSCLES OF THE IRIS
• SPHINCTER PUPILLA
MUSCLE—smooth musclemeiosis—innervated by
parasymp.-short ciliary
nn.
( oculomotor n.)
• DILATOR PUPILLA
MUSCLE—smooth musclemidriasis- innervated by
symp.—sup. cervical symp.
gang.-int. car. a.-long
ciliary nn.
ARTERIES OF IRIS
long posterior ciliary aa.(ophthalmic a.)
• Short posterior ciliary
aa.-(muscular brs.)
•
--MAJOR ARTERIAL
CIRCLE—(at the ciliary
margin)
Brs. From major arterial
circle and anterior ciliary
aa.
--MINOR ARTERIAL
CIRCLE
RETINA
• Innermost layer of
the eyeball.
• The neural- sensory
layer
• Composed of 2
layers
----outer—
PIGMENTED LAYER
----inner--NERVOUS LAYER
ORA SERRATA
• The place where
nervous layer of
retina ends.
• But the pigmented
layer continues
anteriorly over the
back of the ciliary
processes and the
iris—ciliary partiridial part.
PARTS OF RETINA
OPTIC PART
from optic disc-to ora
serrata
pigmented+ nervous
layers present here.
PARS CAECA RETINABlind part.
from ora serrata
Anteriorly.Only
pigmented layer present.
MACULA LUTEA-FOVEA
CENTRALIS
• MACULA
LUTEA=YELLOW SPOT
• Oval yellowish area near
the the centre of
posterior part of retina.
• FOVEA CENTRALIS-is
the central depression
located in the macula
lutea---where VISUAL
RESOLUTION IS HIGH.
HAS ONLY CONES.
OPTIC DISC-araea where
optic n. Leaves the eyeball
• OPTIC DISC = BLIND
SPOT
insensitive to light.
3mm. Nasal to macula
lutea.
--central a. And v.of retina.
---in normal ophthalmoscopic
examinations color= PINK
--- if optic n. Atrophies,color
= WHITE
CENTRAL RETINAL ARTERY
• Courses through optic nerve
fibers
• The first branch of
ophthalmic artery
• Branches
– superior and inferior
each divides into temporal &
nasal brs.
-So 4aa. Supplies each
quadrant of retina.
CENTRAL RETINAL VESSELS
• ARE THE ONLY
VESSELS IN THE
BODY WHICH CAN
BE INSPECTED
DIRECTLY WITH
NAKED EYE
( through an
ophthalmoscope).
OCULAR REFRACTIVE MEDIA
•
•
•
•
CORNEA
AQUEOUS HUMOUR
LENS
VITREOUS HUMOUR
AQUEOUS HUMOR
• Fills the anterior and
posterior chambers.
• Secreted by ciliary
processes-
Functions
-intraocular pressure
-shape of eyeball
-metabolic avenue for
avascular structurescornea, lens.
VITREOUS HUMOR
• Occupies vitreous body
(chamber)- posterior
to lens.
• Colorless,structureless,
transparent gel
LENS
•
•
•
-
Biconvex, transparent body.
Has a capsule.
Central points
anterior pole
posterior pole-AXIS
equator,
faint sutural lines(radii lentis)
devoid of vessels.
ARTERIES AND VEINS OF
EYEBALL
• Artery- Ophtalmic artery
• Veins- Opthalmic veins