anatomy of the eye

1. ANATOMY OF THE EYE
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2. ANATOMY OF THE EYE
1.THE EYEBALL
2. OCULAR ADNEXA

3. THE EYEBALL
• Size-average AP diameter is 21-26mm
• Circumference-72mm
• At birth is appox.16mm
• At age of 3yrs -23mm
• It reaches its maximum size2years very little
growth there after
Has 3 concentric layers
Connected to the brain by optic nerve
Protected by bony orbit and eyelids

6. CORNEA
• Occupies the centre of the anterior pole of the globe
• Size-12mm horizontal meridian
-11mm vertical meridian
-Thickness-1mm
• Bordered-anterioly by precorneal tear film
-posterioly by anterior chamber
• Transparent
• Avascular
• Rich nerve supply-unmyelinated nerve
• Consists of five layers-epithelium
-Bowman’membrane
-Stroma
-Descemet’smembrane
-Endothelium
• Receives most of its nutrient from the aqueous humor and the tear film,
• Most important refractive surface-43 Diopters

8. SCLERA
• Covers posterior 4/5 of the surface of the globe
• Protective coat
• anteriorly ends at the limbus
• Posterioly – forms lamina cribrosa for optic
nerve
• Opaque
• Provide attachment of the extraocular muscles

9. LIMBUS
• Junction between cornea and sclera
• Surgical landmark-cataract, glaucoma
• 2mm wide

10. ANTERIOR CHAMBER
• Filled with aqueous humor
• Lies at the junction of the cornea and iris
• About 3mm in depth
• Angle of the anterior chamber-Seen using
gonioscopy lens
• Aqueous drained through the trabecular
meshwork into canal of schlemn

12. LENS
• Biconvex
• Suspended behind iris by zonules
• Transparent, A-vascular, No nerves
• Grows throughout the life
• Structure: capsule, epithelium, cortex, nucleus
• Functions: Refractive media 15-20 D
Accommodation

14. UVEA
• Middle vascular coat of the eye
• Consist of iris, cilliary body, choroid
• Lies between sclera and the retina
• Main vascular tissue of the eye

15. IRIS
• Most anterior part of the uvea
• Made of blood vessels and connective tissue
• Pigmented-race -melanocytes +pigment cells
• Central perforation –pupil
• It has smooth muscles which regulate the pupil
– Dilator pupillae-dilate- sympathetics
– Sphinter pupillae-constricts-parasmpathetics

18. CILIARY BODY
• Middle part of the uvea
• Triangular in shape
• Functions-1.produce aqueous humor-
Ciliary epithelium
2.Accomodation
3Acqueou humour drainage

20. CHOROID
• Posterior part of the uvea
• Nourishes the outer portion of the retina
• Consist of layers of blood vessels

22. VITREOUS
• Located between lens and retina
• Is a specialized jelly like connective tissue
• Fills the 4/5 of the globe-largest structure
• Volume-4mls
• 99% is water
• Transparent-avascular
Functions
• Serve as route of nutrient to the lens and inner part of
the retina
• Shock absorber

25. RETINA
• Inner coat of the eye
• Thin transparent layer-is in contact with choroid
• Has 2 main layers- outer RPE
-inner neurosensory retina
Divided into 2 parts-central-macula(fovea)
-for day vision
-Peripheral-for night and peripheral vision
Nourished by - choroidal choriocapiliries
- Central retina artery

27. OPTIC NERVE
• It is a 2nd cranial nerve
• Originate in the ganglion layer of the retina
• Length varies -35-55mm from the globe to the
chiasma
• Consist of about one million axons-fibres within
the retina are transparent
• Its organization structure similar to white matter
of the brain
• Optic disc –optic nerve head seen with o’cope
• Within the orbit -covered with meningeal
sheaths
• Blood supply-central retinal artery

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31. OCULAR ADNEXA
• The bony orbit
• Eyelids
• Conjunctiva
• Lacrimal apparatus
• Extraocular muscles
• The accessory organs of the eye

32. THE BONY ORBIT
• 2 conical bony recess
• It is the bony cavity in the skull &
houses
– the eyeball,
– the extra ocular muscles,
– the blood vessels and
– the nerves.
• Orbital bones have air cells-Para nasal
sinuses

33. THE EYELID
• They are movable folds
• Acts like curtain
• Protect the eye against injury ,excessive light
• Help pupil to regulate amount of light reaching
the retina
• Spread tears film by blinking
• Pumping effect-tear drainage
• Has tear producing glands-forms basic tear

34. THE EYELID
• Skin thinnest-transparent elastic , no hair folds
• Orbiculris oculi-roughly circular
-Closes the lids
-Its contraction help tear drainage
-innervation-facial nerve
Tarsal plates-dense fibrous tissue
-Contributes to its form and support
Levator palpebral superioris-elevates upper lids
-Innarvated by 3rd cranial nerve
Mullers muscle-smooth-sympathetics

35. THE LACRIMAL APPARATUS
• It consist- lacrimal gland that secrete
tears
Accessory gland-
• Tear drainage system that drains away
excess tears from the front of the eyes into
the nose

36. LACRIMAL GLAND
• Has 2 parts-orbital-larger-in the lacrimal
fossa-frontal bone
• palpebral-seen of the superiolateral fornix
• Ducts empty into the conjuctival fornix
• Exocrine gland-serous secretion
• Nerve supply –autonomic nervous system

37. PRECORNEAL TEAR FILM
• Covers anterior surface of the cornea and
conjunctiva
• Composed of 3 layers-
• Superficial-oil-lipid layer
• Middle-watery-aqueous layer
• Inner-mucin layer

41. FUNCTIONS OF TEAR FILM
• Lubricates the cornea+conjunctiva
• Produce smooth optical surface
• Provide oxygen + nutrients for the cornea
• Antimicrobial activity-lysozyme,
immunologlobulin
• Mechanical flushing of FB +debris

42. THE LIPID LAYER
• 1.lipid layer-oily-superficial layer
• Secreted- meibomian glands+zeis+Moll
-Sebaceous glands
-Seen as parallel strings of pearls
-Ducts open on the lid margin
Retards evaporation of
tear-aquoeus
Seals the tear film

44. THE AQUOES LAYER
Middle layer- produced by -lacrimal gland
- Accessory glands-Krause and Wolfring
Makes most of the thickness of the tear film
Furnish the basic tear secretion
Structure-identical to main lacrimal gland

45. MUCIN LAYER
inner layer-by goblet cells
-lacrimal gland-small amount
-makes cornea hydrophilic
-important for wetting

46. THE TEAR DRAINAGE SYSTEM
Punta
Lacrymal Gland
Canaliculi
Sac
Nasolacrimal
duct

49. The Lower Punctum

50. CONJUNCTIVA
• Thin, transparent mucous membrane
• Non-keratinized squmous epithelium
• Has goblet cells
• Highly vascularized
• Parts-palpebral-firm adherent to tarsus
-Bulbar-loosely attached to underlying sclera-allows
eye to move-inserts at the limbus
- Fornical-in the fornices

52. EXTRAOCULAR MUSCLES
• Six muscles control the eye movements
• 4 Recti muscles +2 obliques
• The recti originate at a common ring
tendon at the apex of the orbit
• Insertion-anterior portion of the globe
• About 40mm long and 10mm wide
• Insertion forms spiral of Tilux MR,IR,LR
SR

53. EXTRAOCULAR MUSCLES CON
• Oblique muscles
• They control torsional movement
• Upward + downward movement
• IO-arise from the nasal orbital wall
insert-just under the lateral rectus
SO-annulus of zinn
Forms a pulley then inserts to the sclera

55. THE EXTRAOCULAR MUSCLES
There six (6) eye muscles
– The Medial Rectus rotates the eye inward
toward the nose
– The Lateral Rectus rotates the eye outward
toward the temple
– The Superior Rectus turns the eye upward.
– The Inferior Rectus turns the eye
downward.
– The Superior Oblique rotates the eye both
downward and inward toward the nose.
– Inferior Oblique rotates the eye upward
and outward toward the temple

56. FUNCTIONS OF MUSCLES
muscle Primary action
Lateral rectus abduction
Medial rectus adduction
Superior rectus elevation
Inferior rectus depression
Superior oblique
Inferior oblique
Depression
elevation

57. ACCESSORY ORGAN OF THE
EYE
• PLICA SEMILUNARIS
• Cresent-shaped fold of the conjunctiva
• Its epithelium is rich in goblet cells
• Highly vascularized
• Vestigial structure=nictating membrane in lower
animals
• CURUNCLE-ovoid, fresh
• It contains sebaceous glands
• Has colourless fine hair