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Anatomy for lu4
1. Anatomy of the Eye
Dr. Alexander D. Tan
UP-PGH Department of Ophthalmology
and Visual Sciences
2. Objectives
Describe the different anatomic parts of the human
eye
Bony Orbit
Eyelids and Lacrimal Drainage System
Extraocular Muscles
Cornea and Conjunctivae
Uvea, Choroid and Sclerae
Retina
4. Human Orbit
Pear shaped ; Volume: 30 cc
Orbital entrance is 35mm in height and 45mm width
Maximum width is 1 cm behind the orbital margin
Depth 40 to 45mm, medial walls are parallel, lateral
walls are 90 degrees apart
Bones: Frontal, Zygomatic, Maxillary
Bone, Ethmoid, Sphenoid, Lacrimal and Palatine
5. Bones of the Orbit
Roof: Frontal bone and lesser wing of the Sphenoid
bone
Medial Wall: Frontal Process of Maxillary
Bone, Lacrimal Bone, Ethmoid Bone and lesser wing
of Sphenoid
Orbital Floor: Maxilla, Palatine, orbital plate of the
Zygomatic Bone
Lateral Wall: Zygomatic and greater wing of the
Sphenoid Bone
6. Foramina, Ducts, Canals and Fissures
Optic Foramen (lesser wing of Sphenoid): optic
nerve, ophthalmic artery and sympathetic fibers
from carotid plexus
Supraorbital foramen: blood vessels and
supraorbital nerve (branch of CN V1)
Anterior Ethmoidal Foramen, Posterior Ethmoidal
Foramen and Zygomatic Foramen
Nasolacrimal Duct
Infraorbital Canal: infraorbital nerve (V2)
7. Foramina, Ducts, Canals and Fissures
SOF: lacrimal nerve of V1, frontal nerve of V1, CN
IV, SOV; suprior and inf divisions of CN III, nasociliary
branch of V1, sympathetic roots of ciliary ganglion
and CN VI, inferior ophthalmic vein
IOF: infraorbital and zygmatic branches of
V2, orbital nerve from pterygopalatine ganglion and
inferior ophthalmic vein
12. Extraocular Muscles
7 EOMs: Medial Rectus, Lateral Rectus, Superior
Rectus, Inferior Rectus, Superior Oblique, Inferior
Oblique and Levator Palpebrae Superioris
Inserts anteriorly at the Globe: MR, IR, LR, SR (spiral
of Tillaux)
SO: passing through the trochlea to sclera under SR
IO: inserts postero-infero-temporal quadrant
Annulus of Zinn: 4 Recti muscles; above is Levator
SO: sphenoid bone, IO maxillary bone
17. Globe
Not a true sphere: ROC Cornea: 8mm ROC Sclera:
12mm forming an oblate spheroid
Axial length is 23 to 25 mm; transverse distance is 24
mm; total volume os 6.5 to 7 ml
Three Cavities
Anterior Chamber: 3 mm deep; 200 ul
Posterior Chamber 60 ul
Vitreous Cavity (2/3 of the volume of the eye) 5 to 6 ml
Eyeball is Cornea anteriorly and Sclera posteriorly
18.
19. Sclera / Uvea
SCLERA : Opaque and white
Thinnest just behind the insertion of the rectus
muscles ; 1 mm posteriorly, and ; sieve-like at
lamina cribrosa
Generally avascular
Lamina fusca
UVEA: choroid, ciliary body, iris
Highly vascular, nutritive and supportive
RETINA: innermost layer
20. Cornea
Main refractive element of the eye 43 diopters
12 mm horizontal ; 11 mm vertical
1mm thick at the periphery, 0.5 mm thick at the
center
Central 1/3 is nearly spherical (4mm)
Posterior cornea more curved than the anterior
EPITHELIUM: Nonkeratinized, stratified, squamous
epithelium ; 2 to 3 layers of polygonal “wing” cells;
basal cell layer
BOWMANS LAYER: tough layer , does not regenerate
21. Cornea
STROMA: 90% of total thickness; composed of
collagen producing keratocytes, ground
substance, and collagen lamellae; regularity of fibers
maintain transparency
DESCEMET’S MEMBRANE: basal lamina of the corneal
endothelium
Increases thickness with age
Peripheral excresences (Hassal Henle warts)
Central excresences (corneal gutata)
22. CORNEA
ENDOTHELIUM: single layer of hexagonal
cells, 500,000 cells (3,000 cells/mm2)
Maintains corneal transparency and deturgescence
Mitosis is rare, number decreases with age
23.
24. UVEAL TRACT
Main vascular compartment of the eye
Three attachments to the sclera : scleral spur, exit
points of vortex veins and optic nerve
IRIS: determines the size of the pupil, eye
color, sphincter muscle and dilator muscle
CILIARY BODY: formation of the aqueous humor, lens
accomodation, trabecular and uveoscleral outflow of
aqueous humor
Pars plana: 4 mm from limbus ; Pars plicata 70 radial
ciliary processes
Non pigmented epithelium: aqueous formation
Ciliary muscle: longitudinal, radial and circular
25. UVEAL TRACT
CHOROID: nourishes the outer portion of the retina
Three layers: choriocapillaries, middler layer of small
vessels, outer layer of large vessels
Long and short posterior ciliary arteries; anterior ciliary
arteries
BRUCHS MEMBRANE: fusion of the basal lamina of RPE
and choriorcapillaries of the choroid
26. Crystalline Lens
Avascular, 4mm thick and 9 mm in diameter
Lens Capsule, outer cortex and inner nucleus.
Held in place by zonular fibers
Secondary refractive element of the eye
Turns into a cataract
27.
28. Retina
Thin, semi-transparent, multilayered sheet
Receptor and Processor of images
Anterior margin: ora serrata , strongly attached at the ora
serrata and optic disc
0.1 mm thick at the ora serrata and 0.56mm thick at the
posterior pole
MACULA: center of the posterior pole
3 mm of yellowish pigmentation
FOVEA : center of the macula; depression seen producing a
FOVEAL REFLEX
FOVEOLA: most center portion of FOVEA : all photoreceptors
are cones, thinnest part of the retina
29. Retina
Composed of RETINAL PIGMENT EPITHELIUM
AND SENSORY RETINA
RPE: single layer of hexagonal cells, functions to
trap light
Photoreceptors: Rods for dark vision and Cones
for light and color vision
Modulator Cells: Bipolar, Amacrine and
Horizontal cells
Transmitter Cells: Ganglion Cell
31. Retina / Vitreous
Blood supply
Choriocapillaries: outer third of the retina
Central retinal artery: inner 2/3 of the retina
VITREOUS:
2/3 volume and weight of the eye
99% water plus collagen and hyaluronic acid
Notas do Editor
The bony orbit provides a container of the globe and gives protection to its contents.
Fixed volume means, when there is a tumor or swelling … the eyeball is pushed forward resulting in proptosis and when one of the orbital walls are damaged such as in orbital fractures, this results in increase in its relative volume resulting in posterior displacement of the globe or enophthalmos
Supraorbital foramen is located at the medial third of the superior margin of the orbit.
Supraorbital foramen is located at the medial third of the superior margin of the orbit.
Main function of the eyelid is for protection, contains oil gland (Meibomian glands) which form the outermost layer of the tear film, contains the tear drainage, cosmesisMuscles that open the eye are : levatorpalpebraesuperioris, mullers muscle, frontalis muscle ; close the eye: orbicularis ; corrugator supercilii ; procerus muscle
The amount of tears present in our eye is determined by tear production, evaporation, and drainage. The lacrimal drainage system is composed of the punctum, canaliculus and nasolacrimal duct.
Palpebral begins at the mucocutaneous junction of the eyelid and covers the inner eyelid surface; adheres firmly to the tarsusFornix: tissues are redundant and freely movableBulbar Conjunctiva is movable but fuses with the Tenons capsule and inserts into the limbus
Greater variation in fibril separation and diameterGreater degree of fibril interweave
Stem cells in the limbus
Zonular fibers attah primarily in the valleys of the ciliary processes but also along the pars plana
Retina occupies the inner aspect of the posterior 2/3s of the human eye.
The sensory retina is made of layers of cells composed of receptor neurons and glial cells to receive, modulate and transmit images to the brain.Light received by photoreceptors are then processed by modulator cellsTransmitter cells: Transmit the visual impulses from bipolar and amacrine cells to the midbrain
