This presentation gives you detail knowledge of Anatomy and Development of Eye and its structures

2.  Generally referred as globe , eyeball is not
sphere but an oblate spheroid.
 Each eyeball is a cystic structure kept
distended by the pressure inside.

5.  Anterior Posterior diameter: 24mm
 Horizontal Diameter : 23.50mm
 Vertical Diameter: 23mm
 Circumference : 75mm
 Volume : 6.5ml
 Weight : 7 gm

6.  3 coats
1. Fibrous coat (outermost coat)
2. Vascular coats (middle coat)
3. Nervous coat (inner coat )

7.  It is the dense strong wall which protects the
intraocular contents.
 Anterior 1/6th of the fibrous coat is
transparent caller ‘CORNEA’
 Posterior 5/6th is opaque part called ‘SCLERA’
 Junction of the Cornea and Sclera is called
‘LIMBUS’

8.  It supplies nutrition to the vascular structures
of the eyeball.
 It consists of three parts from anterior to
posterior which are : iris , ciliary body and
choroid.

9.  It is concerned with the visual function

10.  Eyeball is divided into two Segments :
1. Anterior Segment
a. Anterior Chamber
b. Posterior Chamber
2. Posterior Segment

12.  It includes crystalline lens and structures
anterior like iris, cornea and two Aqueous
humour filled spaces : anterior and posterior
chamber.

13.  It is bounded anteriorly by the back of the
cornea and posteriorly by the iris and part of
ciliary body.
 The AC is 2.5 mm deep in center in normal
adults.
 Slightly shallow an hyperopes and deeper in
myopes
 Contains about 0.25ml of aqueous humour.

16.  It is a triangular space containing 0.06ml of
AH.
 It is bounded anteriorly by the posterior
surface of the iris and ciliary body and
posteriorly by the crystalline lens and its
zonules and laterally by the ciliary body.

17.  It includes structures posterior to lens viz.
Vitreous humour, retina , choroid and Optic
disc.

18.  Comprises of Optic nerves , OpticChiasma
,OpticTracts, Geniculate Bodies and Optic
Radiations

20.  Each eyeball is suspended by the Extra ocular
muscles and fascial sheaths in a quadrilateral
pyramid shaped bony cavity called as ‘ORBIT’
 Each eyeball is located in the anterior orbit
close to the roof and lateral wall than the
floor and the medial wall

21.  Each eye is protected anteriorly by two
shutters called as ‘EYELIDS’
 The anterior part of the sclera and posterior
surface of the lids is lined by a thin membrane
called as ‘CONJUNCTIVA’

22.  For smooth functioning , the cornea and
conjunctiva are to be kept moist by tears
produced by the lacrimal gland and drained
through lacrimal passages
 These structures together (Eyelid, eyebrows,
conjunctiva and lacrimal apparatus ) are
collectively called asThe appendages of the
eye

24.  The development of the eyeball can be
considered to commence around 22 days
when the embryo has 8 pairs of somites and
is around 2mm in length.
 The eyeball and its related structure are
derived from the following primordia:

25. 1. Optic vesicle, an outgrowth from
prosencephalon (a neuroectodermal structure)

26.  The area of the neural plate which forms the
prosencephalon develops a linear thickened
area on the either side which soon becomes
depressed to form the optic sulcus .

28.  The neural plate is converted into prosencephalic vesicle.
 As the optic sulcus deepens the walls of the prosencephalon
overlying the optic sulcus bulge out to form the optic vesicle.
 The proximal part of the optic vesicle becomes constricted
and elongated to form the optic stalk

30. 2. Lens placode, a specialised area of the surface
ectoderm and the surrounding surface ectoderm.
 Formation of lens vesicle :
 The optic vesicle grows laterally and comes in
contact with the surface ectoderm .
 The surface ectoderm overlying the vesicle becomes
thickened to form lens placode which sinks below
the surface and is converted into the lens vesicle.
 It is soon separated from the surface ectoderm at
33rd day of gestation

32. 3. Formation of the optic cup
 The optic vesicle is converted into a double layered
optic cup.
 The margins of the optic cup grow over upper and
lateral sides of the lens vesicle to enclose it.
 However such a growth does not take place over the
inferior part of the lens , and therefore the walls of
the cup shows deficiency in this part.
 The deficiency extends to some distance along the
inferior surface of the optic stalk and is called as
Choroidal or fetal fissure.

33. 3. Formation of the optic cup

34. 4. Mesenchyme surrounding the optic vesicle

35.  The developing neural tube is surrounded by
mesenchyme which subsequently condenses to
form meninges.
 Later this mesenchyme differentiates to form a
superficial fibrous layer (corresponds to dura) and
deeper vascular layer (corresponds to pia-
arachnoid)

36.  With the formation of optic cup part of the inner
vascular layer of the mesenchyme is carried into the
cup through the choroidal fissure .
 With the closure of the fissure the portion of the
mesenchyme which has made its way into the eye is
cut off from the surrounding mesenchyme and gives
rise to hyaloid system of the vessels

39.  The fibrous layer of the mesenchyme surrounding
the anterior part of the optic cup forms the cornea.
 The corresponding vascular layer of the
mesenchyme becomes iridopupillary membrane
which in the peripheral region attaches to the
anterior part of the optic cup to form the iris.

40.  The central part of this lamina is pupillary
membrane which also forms the tunica vascular
lentis.
 In the posterior part of the optic cup surrounding
fibrous mesenchyme forms the sclera and
extraocular muscles while the vascular layer forms
the choroid and ciliary body.

41.  Retina is developed from the two walls of the optic cup viz.
 a) nervous retina from the inner wall
 b) pigment epithelium from the outer wall.

42. a) Nervous retina
 The inner wall of the optic cup is a single layered epithelium.
 It divides into several layers of cells which differentiate into
the following three layers:
1. Matrix cell layer: cells of this layer form the rods and cones
2. Mantle layer: cells of this layer form the bipolar cells ,
ganglion cells, other neurons of retina and the supporting
tissue.
3. Marginal layer: this layer forms the ganglion cells, axons of
which form the nerve fibre layer.

43. a) Nervous retina

44. b) Outer pigment epithelial layer
 Cells of the outer wall of the optic cup becomes pigmented
 Its posterior part forms the pigmented epithelium of retina
and the anterior part continues forward in ciliary body and
iris as their anterior pigment epithelium.

45. b) Outer pigment epithelial layer

46.  It develops in the framework of optic stalk as below:
1. Optic nerve fibres develop from the nerve fibre layer of the
retina which grow into the optic stalk by passing through
the choroidal fissure (by 6th week of gestation) and pass
posterior to the brain .

47. 2. Glial system of the nerve develops from the
neuroectodermal cells forming the outer wall of the optic stalk.
3.The glial septa surrounding the nerve bundles are composed
of astroglia that differentiate from the cells of the inner wall of
the optic stalk.

48. 4. Sheaths of Optic nerve are formed from the layer of
mesenchyme like meninges of other part of the CNS
5. Myelination of the nerve fibres takes place from brain distally
And reaches the lamina cribrosa just before birth and stops
there .

49. The crystalline lens is developed from the surface ectoderm:
 Primary lens fibres :
 The cells of the posterior wall of the lens vesicle elongate
rapidly to form the primary lens fibres which obliterate the
cavity of the lens vesicle.
 The primary lens fibres are formed upto 3rd month of
gestation and are preserved as the compact core of the lens
known as embryonic nucleus.

50.  Secondary lens fibres :
 These are forms from the equatorial cells of the anterior
epithelium which remains active throughout our life.
 Depending on the period of development the secondary lens
fibres are named as below:
 Fetal nucleus (3rd to 8th month) (Formation ofY suture)
 Infantile nucleus (last week of fetal life to puberty)
 Adult nucleus (after puberty)
 Cortex (superficial lens fibres od adult lens)

51.  Tunica vasculosa lentis
 During embryonic and fetal development, the lens receives
nourishment via an intricate vascular capsule, the tunica
vasculosa lentis that completely encompasses the lens
approximately 9 weeks.
 It is formed by the mesenchyme that surrounds the lens.
 In earlier stage of development it receives abundant arterial
supply from the hyaloid artery.
 Later it received nutrition from aqueous and vitreous.

52.  The lens zonules
 They develop from the Neuroectoderm in the ciliary region.
 The earliest fibres of the Zonular apparatus are a
continuation of the internal limiting membrane that thickens
over the non pigmented epithelium of the developing ciliary
processes.
 Later the zonular fibres are synthesized by the ciliary
epithelial cells and the zonules increases in number ,strength
and coarseness.
 By 5th month of gestation, the zonules have reached the lens
and merge with both the anterior and posterior capsule.

53.  Lens capsule is a true basement membrane produced by the
lens epithelium on its external aspect.

54.  AC arises as a slit in the mesenchyme between the
surface ectoderm and developing iris .
 The mesenchyme anterior to the slit form the
corneal endothelium and that posterior to the slit
forma the primary pupillary membrane.

55.  Angle of anterior chamber is occupied by a nest of
loosely organized undifferentiated neural crest
derived mesenchymal cells that are destined to
develop into the trabecular meshwork.

56.  Schlemm’s canal develops by the end of the 3rd
month of gestation from the channels derived from
the mesodermal mesenchyme.
 Thus the embryonic origin of trabecular cells is
different from that of the vascular endothelial cells
of the schlemm’s canal.

58.  Posterior chamber develops as a split in the
mesenchyme posterior to the developing iris and
anterior to the developing lens .
 The anterior and posterior chambers communicate
when the pupillary membrane disappears and the
pupil is formed.

59.  Epithelium is formed from the surface ectoderm
 Other layers viz. endothelium, Descemet’s membrane,
stroma and Bowman’s layer of mesenchyme lying anterior to
the optic cup

61.  Epithelium is formed from surface ectoderm.
 At about 40 days of gestation corneal epithelium consists of
a superficial squamous cell layer
and a basal cuboidal epithelial
cells layer.
 By the time the eyelids open at
5-6 month of gestation, the
corneal epithelium attains
an almost adult appearance

62.  Endothelium and Descemet’s membrane are formed from
the mesenchymal cells derived from the neural crest which
are situated at the margins of the rim of optic cup.
 At 40 days of gestation endothelium is a 2 layered structure
and by 3rd month of gestation the endothelium becomes a
single layered structure.
 At the 6th month of gestation Descemet's membrane is
demarcated clearly.

63.  Endothelium and Descemet’s membrane are formed from
the mesenchymal cells derived from the neural crest which
are situated at the margins of the rim of optic cup.
 At 40 days of gestation endothelium is a 2 layered structure
and by 3rd month of gestation the endothelium becomes a
single layered structure.
 At the 6th month of gestation Descemet's membrane is
demarcated clearly.

64.  Stroma and Bowman’s layer are derived from the
mesenchymal cells that insinuate between the surface
ectoderm and the developing lens.
 Primary corneal stroma is secreted by basal layer of the
epithelium.
 At about 7th week of gestation the mesenchymal cells
migrate into the primary corneal stroma and contribute to
the further development of the corneal stroma.
 These invading mesenchymal cells differentiate into stromal
fibroblasts or Keratocytes that actively secrete type I
collagen fibrils and matrix of stroma

66.  Bowman’s layer starts forming by condensation of
most superficial acellular part of corneal stroma
after 4 months of gestation and is fully developed
by birth.
 By 5 months the corneal nerves are present,

67.  Sclera is developed from fibrous layer of mesenchyme
surrounding the optic cup(corresponding to dura of CNS)

68.  It s developed from inner vascular layer of mesenchyme that
surrounds the optic cup

69.  The two layers of epithelium of ciliary body develop from the
anterior part of the two layers of optic cup.
 Stroma of ciliary body , ciliary muscle and blood vessels are
developed from the vascular layer of mesenchyme
surrounding the optic cup.

70.  Both layers of epithelium are derived from the marginal
region of the optic cup (neuro ectoderm)
 Sphincter and dilator pupillae muscles are derived from
anterior epithelium (neuro ectoderm)
 Stroma and blood vessels of the iris develop from the
vascular

71. 1. Primary or primitive vitreous is mesenchymal in origin and
is a vascular structure having the hyaloid system of vessels
2. Secondary or defensive or vitreous proper is secreted by
neuro ectoderm of optic cup .this is an avascular structure .
When this vitreous fills the cavity , primitive vitreous with
hyaloid vessel is pushed anteriorly and ultimately
disappears .
3. Tertiary vitreous is developed from neuroectoderm in the
ciliary region and is represented by the ciliary zone.

73.  Eyelids are formed by reduplication of surface ectoderm
above and below the cornea during 2nd month of gestation.

 The folds enlarge and their margins meet and fuse with each
other.
 The lids cut off a space called conjunctival sac.
 The folds thus formed contain some mesoderm which would
form the muscles of the lid and tarsal plate.
 The lids separate after 7th month of intrauterine life.

74.  Tarsal glands are formed by in growth of a regular row of
solid columns of ectodermal cells from the lid margins
 Ciliary glands are outgrowths from the ciliary follicles.
 Cilia develop as epithelial buds from lid margins.

76.  It develops from the ectoderm lining of the lids and covering
the globe.
 Conjunctival glands develop as growth of the basal cells of
upper conjunctival fornix.
 Fewer glands develop from the lower fornix.

77.  Lacrimal gland is formed from the about 8 cuneiform
epithelial buds which grow by the end of 2nd month of fetal
life from the superolateral side of the conjunctival sac.
 Lacrimal sac, nasolacrimal duct and canaliculi: these
structures develop from the ectoderm of nasolacrimal
furrow. It extends from the medial angle of eye to the region
of developing mouth.
 The ectoderm gets burried to form a solid cord.The upper
part form the lacrimal sac.

78.  The nasolacrimal duct is derived from the lower part as it
forms a secondary connection with the nasal cavity.
 Some ectodermal buds arise from the medal margins of
eyelids.
 These buds later canalise to form the canaliculi,.
 The lower lacrimal canaliculus as it extends laterally cuts off
a part of the eyelid with its components which forms
caruncle and plica semilunaris.

80.  The Extraocular muscles are some of the few periocular
tissues that have been shown not to be of neural crest origin.
 The four rectus muscles and the superior and inferior oblique
muscles differentiate from the mesenchyme in the region of
developing eyeball.
 Originally represented as a single mass of mesenchyme ,
they later separate into the distinct muscles, first at their
insertion and later still at their origins.

82.  The EOM’s appear approximately in the following sequence:
Lateral rectus, superior rectus and LPS(5 Weeks), Superior
oblique and medial rectus (week 6) followed by inferior
oblique and inferior rectus.
 III, IV andVI nerve innervate these muscles.

83.  The orbit develops around the eyeball. It is derived above
from the mesenchyme that encircles the optic vesicle below
and laterally from the maxillary process medially by the
frontonasal process and behind by the pre and
orbitosphenoid.
 The orbital bones are formed in the membrane except those
belonging to the base of the skull which develop in cartilage.
 These bones differentiate during the 3rd month and later
undergo ossification.

84.  Initially the optic axes are directed laterally toward the side
of head.
 At birth the orbit is hemispherical
 Although the orbit reaches the adult size by 3 years of age,
the orbit undergoes considerable alterations in shape and
grows progressively until puberty.