Anatomy and Physiology of Optic Nerve Dr. Prabhat Kiran Devkota MBBS(TU), MD(NAMS) Lumbini Eye Institute

1. Anatomy & Physiology of
Optic Nerve
Dr. Prabhat Kiran Devkota
MBBS(TU), MD Resident(NAMS)
Lumbini Eye Institute

2. Presentation Layout
Embryology of Optic Nerve
Introduction
Parts of Optic Nerve
Blood supply
Applied Anatomy

3. Embryology
Neural plate destined to form
prosencephalon @3 wk of gestation
Depression
Optic sulcus formation
Optic sulcus deepens & the walls of
prosencephalon bulge out
Optic vesicle formation
Proximal part of optic vesicle become
constricted & elongated
@4 wk of gestation
Optic stalk formation
Formation of Optic Vesicle and Optic Stalk

4. Embryology of Optic Nerve
It develops in the framework of optic stalk as follows:
• Optic nerve fibres develop from the nerve fibre layer of
retina which grow into the optic stalk by passing through the
choroidal fissure (by 6th week of gestation) and pass
posteriorly to the brain.

5. • Glial system of the nerve develops from the
neuroectodermal cells forming the outer wall of the optic
stalk.
• The glial septa surrounding the nerve bundles are
composed of astroglia that differentiate from the cells of
the inner wall of the optic stalk.
• Sheaths of the optic nerve are formed from the layer of
mesenchyme which surrounds the optic stalk between the
3rd and 7th month of gestation.

6. • Myelination of the nerve fibres begins from the
chiasma at about 7th month, and reaches the lamina
cribrosa just before birth and stops there.
When myelination continues beyond lamina cribosa
medullated nerve fiber is formed.

7. OPTIC NERVE ANATOMY

8. HISTORICAL REVIEW
 Aristotle described optic nerves as joining at the optic
chiasm, so-called because it resembles the Greek letter
“‫(”א‬chi).
 In 150AD , Galen gave a more detailed description of
the optic nerves as sensory in nature but incorrectly as
hollow and continuous with the ventricular system.
 Gratiolet, 1700 years later. Using soft orangewood
sticks for blunt dissection was able to follow the
retinofugal projection to the pretectum as well as to
confirm the main pathway to the lateral geniculate
nucleus.

9. OPTIC NERVE
 2nd Cranial Nerve
 47-50 mm in length
 Starts from Optic Disc to the Optic Chiasm.
 It is the backward continuation of the Nerve fiber
layer of the Retina which consists of 1.2 million
axons.
 Also contains afferent fibres of light reflexes and
some centrifugal fibers.

11. Special Features of Optic Nerve
 Outgrowth of brain
 Not covered by neurilemma so doesn’t
regenerate when cut.
 Very thin fibres (2-10microns in diameter) &
million in number
 Surrounded by meninges unlike other peripheral
nerve
 Both the primary and secondary order neurons
are in the retina.

12.  1st order neurons:
Bipolar cells of retina.
 2nd order neurons:
Ganglion cells of retina.
Their axons form Optic Nerve
 3rd order neurons:
Neurons in the lateral geniculate body.
Their axons terminate in primary visual cortex.

13. Arrangement of Nerve Fiber in Retina
 Fibres from the nasal half of the
retina come directly to the optic disc
as superior and inferior radiating
fibres (SRF & IRF).
 Fibres from the macular region
pass straight in the temporal part of
the disc as papillomacular bundle
(PMB).
 Fibres from the temporal retina
arch above and below the macular
and papillomacular bundle as
superior and inferior arcuate fibres
(SAF & IAF) with a horizontal raphe
in between.

14. Arrangement of Fiber in Optic Nerve
In the optic nerve head:-
 Fibers from the peripheral part of the retina:
- lie deep in the retina
- occupy the most peripheral part of the optic disc
 Fibers originating closer to the optic nerve head:
- lie superficially in the retina
- occupy a more central portion of the disc

15. In the distal region (just behind eye):-
 Exactly as in retina
- i.e. upper temporal & lower temporal fibers are situated
on the temporal half of the optic nerve
- separated from each other by a wedge shaped area
occupied by the Pmb
 The upper nasal and lower nasal fibers are situated on
the nasal side

16. In the proximal region (near chiasma):-
The macular fibers are centrally placed

17.  Thickness of Nerve Fiber Layer of Disc:-
Thickness progressively increases in the following order:
• Lateral quadrant (thinnest)
• Upper and lower temporal quadrant
• Most medial quadrant
• Upper and lower nasal quadrant (thickest)
Clinical Significance:-
• Papilloedema appears first in the thickest and last in the
thinnest quadrant.
• Arcuate nerve fibres are most sensitive to glaucomatous
damage.
• Macular fibres are most resistant to glaucomatous
damage.. So there is retention of the central vision till end.

18. AXONS:-
 Axons permit signals to be transferred from the retina to
the primary visual nuclei.
 Conduction velocities in large, myelinated fibers (about 20
m/second) are much faster than the velocities in small,
unmyelinated fibers (about 1 m/ second).
 Axons permit the transfer of intracellular chemicals and
organelles such as mitochondria from the neuron soma to
the distal terminal and vice versa.
 Orthograde (eye to brain) axoplasmic transport has a
slow component that progresses at 0.5–3.0 mm/day and a
rapid component that moves at 200–1000 mm/ day.
 Retrograde (brain to eye) axonal transport also occurs at
an intermediate rate.

19. Photoreceptor RGCs:-
 P cells are smaller cells, concentrated in the macula, and
contribute axons of small caliber and have color-opponent
physiology and are thought to subserve high-contrast, high-
spatial-frequency resolution
 M cells are larger cells that contain large, fast-conducting
axons and about 5%–10% of the RGC & involved primarily
with noncolor information of high-temporal and low-spatial
frequency.
 Melanopsin retinal ganglion cells (mRGCs) belong to a
newly discovered class that subserve the autonomic
functions including pupils and circadian rhythms.

20. GLIA:-
 Oligodendrocytes are specialized glia for axonal
myelination. Myelination begins centrally during
development and stops at the lamina cribrosa of the
optic disc at birth.
 Microglia and macrophages are cells that derive from
the immune system and can move readily into the CNS
from the vascular beds. The apoptosis of RGCs during
development/diseases, is modulated by these glial cells.
 Astrocytes have extensive neurofibrillary processes that
spread among the nerve fibers. These specialized glial
cells line the borders between axons and other tissues
and form part of the blood–brain barrier. When axons are
lost in optic atrophy, astrocytes move and proliferate to
fill the empty spaces.

21. Optic Nerve Parts:-
47 to 50 mm in length
1.INTRAOCULAR PART (1mm)
2.INTRAORBITAL PART (25mm)
3.INTRACANALICULAR PART
(5-9 mm)
4.INTRACRANIAL PART (10-16mm)

22. 1. Intraocular Part (Optic Disc)
SNFL Prelaminar Lamina Cribrosa Retrolaminar
 Passes through the Sclera through Lamina Cribrosa,
Choroid and finally appears inside the eye as Optic
Disc.
 Average diameter of the optic nerve head is 1.5 mm
but expands to 3 mm behind sclera due to presence
of myelin sheath.
 Divided into 4 portions (from anterior to posterior):
Intraocular Part

24. a. Surface Nerve Fibre Layer
Composed of axonal bundles (94% nerve fibers of
retina + 5% astrocytes).
Optic Disc is covered by thin layer of astrocytes,
Internal Limiting Membrane of Elschnig which
separates it from vitreous.
Central portion of membrane gets thickened:
Central meniscus of Kuhnt.
Near optic nerve, all layers of retina (except NFL)
are separated from it by a partial rim of glial tissue:
Intermediate tissue of Kuhnt.

26. b. Prelaminar region
Increased number of astrocytes and neurons
Border tissue of Jacoby (cuff of astrocytes)
seperates the nerve from Choroid.
D/t this reason disc swells so easily in papilloedema
while adjacent retina does not

27. c. Lamina Cribrosa
.
 Fibrillar sieve like structure with fenestrations, 200-300 holes
 Made of fenestrated sheets of scleral connective tissue lined
by glial tissue.
 Comprises approx. 10 connective tissue plates, integrated
with sclera and whose pores transmit the axon bundles
 A rim of collagenous connective tissue with admixture of
glial cells which intervenes between the choroid and sclera
and optic nerve fibres is called the border tissue of
Elschnig.
 Rich blood supply from the circle of Zinn.

29. d. Retrolaminar Region
Astrocytes decrease and Oligodendrocytes
increase to cause myelin
Addition of myelin sheath doubles diameter of ON
(from 1.5mm to 3.0 mm) as it passes through sclera
Axonal bundles are surrounded by connective
tissue septa
Posterior extent of retrolaminar region is not
clearly defined

30. Optic Nerve Head:-
Extends from its anterior surface in contact with
vitreous to a plane which is level with that of
posterior scleral surface(1mm).
 Optic Disc part of nerve head visible with
ophthalmoscope.
 Intra papillary parts:-
-optic cup & neuroretinal rim
-separated by scleral ring of Elschnig

32. Ophthalmoscopic Features of Optic
Nerve Head
Optic Disc Colour
• It is pink in colour
• Most noticeable inferotemporally
• The cup is white in colour
• In chronic glaucoma as axons are lost, its pores become
more visible as the cup enlarges.
Disc Shape
• May be round but usually
oval.

33. Disc Size:-
• Normal Area- 0.86 to 5.54mm2 with a mean of 2.69mm2
• Diameter about 1.5mm horizontally ,1.75mm vertically
(Vertical diameter – 9% longer than its horizontal)
• It corresponds with the size of internal opening of the
scleral canal.

34. Macrodisc: area >2SD above the mean ( >4.09mm2)

35. a. Primary macrodisc- Morning Glory syndrome

36. b. Secondary macrodisc- high myopia, buphthalmos
may reach up to 20mm2

37. Microdisc: area <2SD below mean (<1.29mm2)
 Small optic disc
 smaller number of optic nerve fibers
 smaller scleral canal
Non arteritic ischemic optic neuropathy :
is common in small disc- d/t vascular perfusion
problem & limited space

38. • A funnel shaped depression not
occupied by neural tissue
• Varies in form and size
• Mean optic cup area is 0.72 sq mm.
• Location- slightly temporal to its
geometric centre.
• Cup area correlates with the disc
area
• Normally cup is horizontally oval
• Chronic glaucoma—vertically oval
cup
OPTIC CUP:

39. NEURORETINAL RIM:
• The tissue outside the cup is termed as neuroretinal rim
• Rim area ranges from 0.8- 4.66mm2 and correlates the
disc area
• Broadest in the Inferior segment of the disc –then
Superior – then Nasally-then Temporally is the narrowest
(ISNT rule)

40. • Typical rim configuration correlates
– with the diameter of the retinal artery and vein
– with the nerve fibre visibility
– with the location of the foveola inferior to the optic
disc centre.

41. • In Primary Open Angle & other Chronic Glaucoma a
progressive loss of retinal ganglion cells occurs.

42. • Characteristic pattern of axonal loss
at the neuroretinal rim with
enlargement of cup –upper and
lower poles of the disc
• Flame shaped hemorrhages on the
rim (inferior or superior temporal
margin) is seen in the glaucomatous
optic nerve damage

43. CUP/DISC RATIO
 It is the ratio of cup and disc width measured
in the same meridian--- vertical or horizontal
 Median value of 0.3:1

44.  Increases in chronic glaucoma.
 Does not differ by more than 0.2 between the 2 eyes
in 99%.
 Asymmetry of >0.2, signify enlargement & has
diagnostic importance in glaucoma.
 A vertical cup/disc ratio of <=0.4 signifies no glaucoma
 In small disc, ratio of 0.2-0.3 is significant
 In primary macro disc ratio of 0.8 may be entirely
normal

45. PARAPAPILLARY CHORIORETINAL ATROPHY
• A crescentic region of chorioretinal atrophy is a
common finding at the temporal margin of normal
disc
• It is exaggerated in Chronic glaucoma or in high
myopia
• 2 zones: zone alpha
zone beta

46. Zone alpha:
 More peripheral
 It is an irregular hypo or hyper pigmented region
associated with irregularities of the RPE and
parapapillary choroid
 It corresponds to choroidal crescent
 It contributes to relative scotoma

47. Zone beta:-
 Related to the disc centrally and to the retina or zone
alpha peripherally
 It consists of larger choroidal vessels & a marked
atrophy of pigment epithelium and choriocapillaris
 It corresponds to sclera crescent
 It contributes to absolute scotoma

48. • These zone enlarges in Chronic glaucoma

49. RETINAL VESSELS:
• Emerges on the medial side of the cup
• Slightly decentered superonasally

50. • Ophthalmoscopically what is seen is the blood
column & not the vessel wall
• Light reflex is lost in papilloedema as the vessels
bend over the elevated disc margin
• Venous pulsation- 15-90% of normal subjects &
is d/t pulsatile collapse of the veins as ocular
pressure rises with arterial inflow into the uvea
• Visible arterial pulsation is pathological – it
implies high IOP or aortic incompetence

51. 2.Intraorbital part

52. •Extends from back of eyeball to the optic foramina.
•Sinous path to allow movements.
•Covered by dura, arachnoid and pia.
•The CENTRAL RETINAL ARTERY with the VEIN enters the
nerve on its Inferiomedial aspect about 10 mm from the
eyeball.
•Anteriorly:- seperated from EOM by orbital fat.
•Posteriorly:- Near the optic foramina, surrounded by annulus
of zinn and origin of 4 rectus muscle.

53. •Some fibres of SR & MR muscles adherent to its sheath,
causes painful ocular movements in retrobulbar neuritis.
•Long and short ciliary nerves and arteries surround the optic
nerve before these enter the eyeball.
•Laterally:- between the optic nerve and lateral rectus muscle
are situated the Ciliary Ganglion, divisions of the
Oculomotor nerve(3rd CN), the Nasociliary nerve,
Sympathetic nerve and Abducens nerve(6th CN).
•Ophthalmic artery, superior ophthalmic vein and the
nasociliary nerve cross the optic nerve superiorly from the
lateral to medial side.

55. 3.Intracanalicular Part

56. • Optic canal lies within the lesser wing of sphenoid
bone and is about 5mm long.
• Closely related to ophthalmic artery which crosses
nerve inferiorly from medial to lateral side in dural
sheath & leaves sheath at orbital end of canal.
• Sphenoid and post. ethmoidal sinuses lie medial
to it and are separated by a thin bony lamina.This
relation accounts for retrobulbar neuritis
following infection of sinuses.

58. 4. Intracranial Part

59. • lies above the cavernous sinus and converges with
other side over diaphragm sellae to form chiasm.
• Around 1mm Length, 4.5mm Diameter.
• ensheathed by pia mater only but receives
arachnoid & dural sheaths at point of its entry into
optic canal.

60. •Internal carotid artery runs first below and lateral to it.
The Ophthalmic Artery arises from internal carotid artery
below the optic nerve.
•The Anterior Perforated Substance, medial root of the
olfactory tract and Anterior Cerebral Artery lie above
this part of the optic nerve

61. •Intracranial portion only has the PIAMATER.
•Intracanalicular and intraorbital portion has all three
layers of the meninges
MENINGEAL SHEATHS OF THE OPTIC NERVE

62. •Meningeal sheaths & subarachnoid space and the
subdural spaces around the optic nerve are continous with
that of brain.
•Anteriorly all 3 meningeal sheaths terminate at the
sclera(at level of lamina cribrosa).
•At apex of the orbit, dura splits into two. the outer gets
continious with the periosteum of orbit, inner forms the
dural sheath of optic nerve.

63. • Arachnoid layer is connected to pia with numerous
trabeculae “pia-arachnoid meninx’’, containing
cerebrospinal fluid.
• Pia mater sends numerous septa into the optic
nerve, dividing its fibres into fascicles. These septa
are admixture of 'pia-glia'.

64. Blood Supply of Optic Nerve:
Circle of Willis

65. A. Intraocular part

66. b) PRE-LAMINAR
REGION
•Capillaries derived from RETINAL
ARTERIOLES, which anastomose with vessels
of Prelaminar region.
•Occasionally from the CILIORETINAL
ARTERY, ciliary derived vessel from prelaminar
region
•Supplied by VESSELS OF CILIARY
REGION
•These vessels may be derived from
PERIPAPILLARY CHOROIDAL VESSELS
or from SHORT POSTERIOR CILIARY
VESSELS
a) SURFACE
NERVE
FIBRE LAYER

67. •Supplied by the CILIARY VESSELS
•These vessels are derived from SHORT
POSTERIOR CILIARY ARTERIES and
ARTERIAL CIRCLE OF ZINN-HALLER
c) LAMINA
CRIBROSA
REGION
•Supplied by both CILIARY AND RETINAL
CIRCULATION
•Ciliary circulation comes from RECURRENT
PIAL VESSELS.
•CENTRAL ARTERY OF RETINA provides
Centripetal and Centrifugal branches.
d) RETRO
LAMINAR
REGION

68. B . Intraorbital part
1. Periaxial System of vessels
2. Axial System of vessels

69. .
Periaxial
system of
vessels
Axial
system of
vessels
• Intraneural b/o central retinal
artery.
• Central collateral b/o central
retinal artery.
• Central artery of optic nerve.
• Derived from branch of
internal carotid artery:
Ophthalmic a.,
long & short posterior ciliary artery.
Lacrimal artery.
Central artery of retina
Circle of Zinn

71. C .Intracanalicular part
D. Intracranial part :
Periaxial system of vessels.
B/o internal
carotid artery
B/o anterior
cerebral artery
B/o
ophthalmic
artery
Twigs from
Anterior
Communicatin
g
Artery

72. Venous drainage :
Optic nerve
head
• Central retinal vein
Orbital part
• Peripheral pial plexus
• Central retinal vein
Intracranial
part
• Pial plexus which ends in
anterior cerebral & basal vein

73. APPLIED ANATOMY:-

74. Optic Disc Coloboma
Results from an incomplete closure of the embryonic fissure
Disc appears enlarged and incorporates a sharply
demarcated, glistening white, bowl-shaped excavation
inferior rim of the disc is thinner, which reflects the position of
the embryonic fissure.
remaining neural tissue lies superiorly in a C-shaped or
moon-shaped crescent

75. associated with genetic syndromes :-
CHARGE [coloboma of the eye, heart anomaly, choanal
atresia, retardation, and genital and ear anomalies],
Walker–Warburg syndrome,
Goltz focal dermalhypoplasia,
Goldenhar’s syndrome,
linear nevus sebaceus syndrome

76. Inferior rim: thin or absent, superior rim -relatively normal
enlarged disc, sharply demarcated, glistening white bowl-shaped excavation
moon-shaped crescent (sup.)

77. Myelinated nerve fiber:-
■ Myelination of the nerve fibres begins from the chiasma at
about 7th month, proceeds distally and reaches the lamina
cribrosa just before birth and stops there.
After birth in some cases, this extends up to around the optic
disc and presents as congenital opaque nerve fibres.
■ White lesions with feathery edges which radiates outward
from the disc following NFL Bundles
■ Peripheral edges fanned out
■ Simulates disc edema

78. whitish lesions with feathery fanned out edge

79. Optic Disc Pit:-
■ Round or oval, gray, white, or yellowish crater-like
depression in the optic disc
■ commonly involve the temporal optic disc & often
associated with adjacent peripapillary retinal
pigment epithelium changes.
■ most common visual defect appears to be a
paracentral arcuate scotoma connected to an
enlarged blind spot.

80. round or oval, gray, white, or yellowish crater

81. Histologically, an optic pit is a herniation of rudimentary
neuroectodermal tissue into a pocket-like depression within the
nerve substance.

82. Congenital Tilted Optic Disc Syndrome:-
•Occurs when nerve exits the eye at an oblique angle.
•Nonhereditary bilateral condition in which the
superotemporal optic disc is elevated and the inferonasal
disc is displaced posteriorly, which makes an optic disc oval
with its long axis obliquely orientated.
•Accompanied by :-
situs inversus of the retinal vessels,
congenital inferonasal conus,
thinning of the inferonasal RPE and choroid, and
myopic astigmatism.

83. • Visual Field Defect:- bitemporal hemianopias, which
involve primarily the superotemporal quadrants.
• Superotemporal disc: raised, simulating disc swelling
• Inferonasal disc: flat or depressed

84. Oblique Disc configuration
Superotemporal disc is elevated and the inferonasal disc is displaced posteriorly

85. Optic disc Drusen
Blockade of orthograde axoplasmic flow
Deposition of hyaline material within the optic nerve head
that is occasionally associated with ocular and systemic
disorders.
Globules of mucoproteins & mucopolysaccharides that
progressively calsify in the optic disc
Thought to be the remnants of the axonal transport
system of degenerated retinal ganglion cells.

86. Signs:-
Elevated, ‘lumpy’-looking non hyperaemic disc.
No physiological cup.
Disc vessels are not obscured as they pass over the disc.
Emerging vessels are more numerous and show anomalous
branching patterns.
Peripapillary retinal nerve fibre layer is usually normal.
With age they enlarge and become exposed above the disc
surface

87. Morning Glory Disc
■ Congenital funnel shaped excavation of the posterior
globe
■ Optic disc is enlarged, orange or pink in color,
■ variably elevated annular zone surrounds the disc
with irregular areas of pigmentation and
depigmentation
■ White tuff of glial tissue covers central portion of cup
■ blood vessels appear increased in number, arise
from the periphery of the disc, run an abnormally
straight course over the peripapillary retina, and tend
to branch at acute angles

88. ■ macula may be incorporated into the excavated
defect (macular capture)
■ associated with transsphenoidal encephalocele
and with hypoplasia of the ipsilateral intracranial
vasculature

89. disc enlarged ,irregular areas of pigmentation and depigmentation
blood vessels increased ,abnormally straight, branching at acute angles

90. Optic Nerve Hypoplasia
■ subnormal number of optic nerve axons with normal
mesodermal elements and glial supporting tissue.
■ small, gray, or pale optic nerve head, surrounded by
a yellowish mottled peripapillary halo, flanked on
either side by a ring of pigment (double-ring sign).
■ Septo-optic dysplasia (de Morsier syndrome):-
optic nerve hypoplasia,
absence of the septum pellucidum, and
partial or complete agenesis of the corpus callosum.

91. small, gray, or pale optic nerve head, surrounding yellowish mottled peripapillary halo-
double-ring sign

92. Aicardi syndrome
Rare X linked genetic disorder
Major features:-
infantile spasms,
agenesis of the corpus callosum,
modified hypsarrhythmia on EEG, and
a characteristic optic disc appearance that consists of
multiple depigmented chorioretinal lacunae clustered around
the disc.
Associated with vertebral and costal malformations & severe
mental retardation

93. multiple depigmented chorioretinal lacunae clustered around the disc.

94. Megalopapilla
■ Abnormally large optic disc that lacks the inferior excavation
of optic disc coloboma or the numerous anomalous features
of the morning glory disc anomaly
■ Bilateral and associated with a large cup-to-disc ratio
■ Often suspected to have glaucoma. however, the optic cup
is usually round or horizontally oval with no vertical notch or
encroachment
■ Area > 2.5 mm²
■ Pale NRR

95. ■ Visual acuity is normal or mildly decreased .
■ Visual fields usually normal except for an enlarged blind
spot.

96. Abnormally large cup-to-disc ratio

97. Congenital Optic Disc Pigmentation
 rare condition
 melanin anterior to or within the lamina cribrosa
imparts a gray appearance to the disc.
 presents with good visual acuity but may
coexistent with optic disc anomalies that decrease
vision.

99. Papilloedema:-
Optic Disc edema, usually bilateral, which results from
increased intracranial pressure.
Etiology:
intracranial space occupying lesions
obstructions of the arachnoid villi,
CSF producing tumors and
idiopathic intracranial hypertension (IIH)

100.  Mechanical signs:
• Blurring of the optic disc margins.
• Filling in of the optic disc cup.
• Anterior extension of the nerve head (3D=1 mm elevation).
• Edema of the nerve fiber layer.
• Retinal or choroidal folds or both.
 Vascular signs:
• Venous congestion of arcuate and peripapillary vessels.
• Papillary and peripapillary hemorrhages.
• Nerve fiber layer infarcts (cotton-wool spots).
• Hyperemia of the optic nerve head.
• Hard exudates of the optic disc.

101. Blurred disc margin, Anterior extension of ONH, Edema, Retinal or choroidal folds
Venous congestion, Hyperemia, hemorrhages, cotton-wool spots

102. OPTIC ATROPHY
White, flat disc with a clearly delineated outline
Reduction in the number of small vessels on the
disc.
Attenuation of the peripapillary vessels.
Thinning of the retinal nerve fibre layer.
Causes:-
Optic neuritis, Compression, Primary hereditary
optic atrophies, Hereditary neurological disorders,
Toxic, Nutritional deficiency, Trauma

103. White flat disc, reduced vessel, Attenuation & Thinning of RNFL

104. REFERENCES
Fundamentals and Principles Of Ophthalmology-AAO
Neuro Ophthalmology – AAO
Snell’s anatomy
Wolff’s Anatomy
Ophthalmology – M.Yanoff
Clinical ophthalmology – Kanski 9th edition