This document discusses the anatomy and clinical significance of the optic nerve. It begins with a brief overview of the embryology and development of the optic nerve, from the formation of the optic vesicle and stalk in the early weeks of gestation through myelination and vascularization later in development. Next, it describes the anatomy of the optic nerve in detail at each stage from the intraocular portion to the visual cortex, including structures like the optic disc, chiasm, tract, lateral geniculate body, and optic radiation. The document concludes with a discussion of the clinical significance of understanding optic nerve anatomy, highlighting conditions like disc edema, congenital anomalies, vascular diseases, and how lesions at different points can cause different visual field defects.

1. Anatomy of optic nerve and its clinical
Significance
• Presented By
• Pabita Dhungel
• B. Optometry
• 2nd
year
• Institute of Medicine
1

2. References
• Walsh and Hoyt’s clinical Ophthalmology
• Wolf’s anatomy
• Duane’s Ophthalmology-2005
• AAO – Fundamentals & Principles of
Ophthalmology-sec 2
• Embryology – Duke Elder
• Anataomy and physiology of Eye – A.K
Khurana 2nd
edition
2

3. Presentation layout
• Embryology of optic nerve
• Introduction
•Blood supply
•Few optic nerve diseases
•Summary
3

4. Formation of optic vesicle and
optic stalk
• Neural plate destined to form prosencephalon
depresses to form optic sulcus
•Neural plate converts into prosencephalic
vesicle
•Optic sulcus deepens and prosencephalon
bulge out to form optic vesicle
•Proximal part of optic vesicle becomes
constricted and enlongated to form optic stalk
4

5. 5

6. Embryology of optic nerve
Optic nerve head
The optic nerve head is formed late in the
embryonic period as the optic nerve stalk
encloses the hyaloid artery(8th
week,20-mm
stage)
From the hyaloid artery ,the vascular bud
develops(13th
week,96-mm) within Bergmeister
papilla and through it into the nerve fibre layer
of the retina
6

7. Contd…
• Glial cells form the sheaths of the vessels
• Eventually hyaloid artery disapears before
birth, Bergmeister’s papilla becomes atrophic,
and the physiological cup of the optic disc
develops at 15th
week of gestation
• Optic nerve
• Develops from embryonic optic stalk at 4th
week and connects the optic vesicle to
forebrain
7

8. Contd…
Week of
Gestatio
n
Length
(mm)
Developing events
4 2.5-
6mm
Short optic stalk
5 5-9mm Development of hyaloid vasculature
6 8-14mm Embryonic cleft closes
7 13-
18mm
Growth of the axon, formation of optic nerve
8 18-
31mm
Stalk fully occupied by axon, axons of optic nerve reaches the
retina, rudimentary optic chiasm established, optic nerve
vascularization starting to form, optic nerve head starting to
form
8

9. Contd…
Week of
gestation
Length
(mm)
Developing events
11 65-
73mm
Vascular-connective septa invade the nerve
12 80mm Pia mater, arachnoid, and dura mater distinguishable, glial
filaments appear
14 105mm Subarachnoid spaces appears
15 117-
123mm
Physiological cup starts to form
18 160mm Vascularization of the optic nerve completed
23 220mm Myelinization starts
9

10. Embryology contd…
• Glial elements are formed from 9th
week
(45mm stage) to 18th
week
• Vasculature develops at 11th
week(65-73mm)
in the same way as CNS
10

11. Anatomy of optic nerve
• Optic nerve- more than 1 million axons.
• Starts from optic disc upto optic chiasma.
• Backward continuation of the nerve fiber
layer of retina.
• Consisting of axons originating from ganglion
cells.
• Contains the afferent fibers of light reflex.
• Elongated tract of white matter
• Not covered by neurilemma.
11

12. Contd…
• Optic nerve divided in topographic areas.
Intraocular portion of optic nerve-
optic disc or nerve head,pre laminar and post
laminar.
Intraorbital portion.
Intracanalicular portion.
Intracranial portion.
12

13. 13

14. Intraocular optic nerve
• 1 mm in length.
• 1.5 mm diameter.
• Which expands approximately 3-4 mm behind
the sclera.
• Optic nerve head divided in 4 parts(ant to
post)
14

15. Intraorbital optic nerve
Relation of ophthalmic artery
Initially infero-lateral-medially
At the optic foramen-inferior and lateral
Lateral to optic nerve (in posterior orbit)
-Inferior division of 3rd
nerve
-Nasociliary artery
-Sixth Nerve
-Ciliary ganglion
15

16. 16

17. Intraorbital optic nerve
At the orbital apex – optic nerve surrounded
by annulus of Zinn.
Blood supply - Ophthalmic artery with
meningeal branches
17

18. Intracanalicular optic nerve
• 9 mm
• Tightly fixed within the canal (compressive
optic neuropathy)
• Blunt trauma
• Optic nerve edema
• Blood supply - pial branches from ophthalmic
artery.
18

19. Intracranial optic nerve
• Length-10mm
• Dm-4.5mm
Extends post & medially ascending at an angle
of 45º to join the chiasma
Blood supply- pial vessels arising from ICA
branches from ant cerebral and anterior
communicating artery
19

20. Optic nerve head
 4 layers of Optic Nerve Head:
• Surface nerve fiber layer.
• Prelaminar layer consisting of retinal nerve
fibres angled posteriorly from the plane of
retina visible only within the central cup.
• Laminar layer: Lamina cribrosa and nerve fibre
bundles running through it.
• Retro laminar layer.
20

21. 21

22. Optic nerve head
• Lamina Cribrosa - Consists of series of plates
of collagenous connective tissues.
• -Perforated by 200 - 400 openings.
• -Superficial openings – appear as grey
dots deep within the optic cup.
• -Large pores have thin connective
tissue supports and contain large
nerve fibres.
22

23. Contd…
• Optic Cup - 3-dimensional pale depression in
the centre. Size of the cup related to dm of
the disc.
• Neuroretinal rim- tissue between outer edge
of the cup and outer margin of the disc.
• Orange or pink colour
• Uniform width
• Retinal blood vessels
23

24. 24

25. 25

26. Optic chaisma
Nerve fibres:-
Lower nasal fibres traverse the chiasma low
and anteriorly (vulnerable-expanding
intrasellar lesions)
Upper nasal fibres traverse high and posteriorly
(craniopharyngioma)
Crossing fibres from infero-nasal quadrant
loop ant into post part of contralateral optic
nerve –Wilbrand’s Knee 26

27. 27

28. Optic tract
• Each optic tract contains ipsilateral temporal
& contralateral nasal fibres from optic nerves.
• Nerve fibres rotates a 90º so that superior
fiber – medially & inferior – laterally .
• Macular fibres - dorsolateral orientation.
• Blood supply - anterior choroidal artery &
branches from posterior communicating
artery.
28

29. Contd…
• Visual field defects in optic tract lesion
• incongruous homonymous hemianopia
• Bilateral retinal layer atrophy / optic atrophy
• Pupillary reflex – RAPD in contralateral eye
29

30. Lateral geniculate body
Part of Thalamus
• Site of termination of afferent fibres
• 6 major layers:-
Magnocellular (1 ,2 )
Parvocellular (3,4,5,6 )
• Visual field defect in lesions of LGB
• Incongrous homonymous hemianopia
• No pupillary change
30

31. Contd…
• Primary target of optic tract is dorsal lateral
geniculate body(dLGB), a thalamic neuclei
• dLGB consists of 3 distinct regions
• Dorsal four layers, consisting small neurons
called parvo, or P-cells, are parvocelluar layers
• Larger neurons called magno or M- cells
comprises two ventral magnocellular layers
• Intermediately lies small konio cells
31

32. Contd…
• Parvo, magno and konio pathways are
referred to as parallel pathways
• Parvo pathway encodes detail and color while
magno pathway encodes fast movement
• The role of konio pathway is less well
understood
32

33. Optic radiation
• 3 main groups:-
- Inferior portion (serving superior V.F.)
- Superior portion (serving inferior V.F.)
- Central portion (macular fibres)
• As they exit from LGB the rotation of fibres
occurs in reverse 90º so superior fibres lie
superiorly and inferior fibres lie inferiorly.
• Blood supply:- anterior choroidal artery &
posterior cerebral artery
33

34. Visual cortex
• Thinnest portion of cerebral cortex
• Area - 20-45 sq cm
• Occupies 3-5% of brain
• Situated along calcarine fissure on medial
side
• Macular fibres – tip of occipital lobe and tip of
lateral side
• Ocular Dominance Column
34

35. 35

36. Visual cortex
• Blood supply: Middle cerebral artery
Posterior cerebral artery
• Visual field defect - occlusion of the Posterior
cerebral artery - congruous homogeneous
hemianopia
• Head injury, gun shot injury, cerebral
tumours.
36

37. 1 lesion of optic nerve
2..lesion through thru proximal
part
3.Sagittal (central) lesion of
chaisma
4.Lateral chaismal lesion
5. Lesions of optic tract
6. Lesions of LGB
7. Lesion of optic radiation in
temporal lobe
8. Lesions of optic radiation in
parietal lobe
9.Optic radiation
10.Visual cortex sparing
macula 37

38. Blood supply
• Intraocular part-
a)surface nerve fiber-capillaries from retinal
artery.
b)prelaminar-short post ciliary artery.
c)lamina cribrosa-short post ciliary artery and
circle of Zinn-Haller.
d)retrolaminar-ciliary and retinal circulation.
38

39. 39

40. Contd…
• Intraorbital part-
a)periaxial system-internal carotid artery.
ophthalmic artery
long posterior ciliary artery
short post ciliary artery
lacrimal artery
central artery of retina
circle of Zinn
40

41. Contd…
b)axial system-
intraneural branches of central retinal artery
central collateral arteries
central artery of optic nerve
41

42. Contd…
• Intracanalicular part-
ophthalmic artery &
periaxial system
42

43. Contd…
• Intracranial part-
periaxial & pial plexus(4 sources)
internal carotid artery
anterior cerebral artery
ophthalmic artery
anterior communicating
artery
43

44. 44

45. Venous drainage
• Primarily by central retinal vein.
• Orbital part –pial plexus and central retinal
vein.
• Intracranial part-anterior cerebral and basal
vein.
45

46. •Clinical significance of
optic nerve
46

47. • Optic nerve is formed by axons of 1.2 million
ganglion cells of retina
• Measures about 1.5mm in diameter and lies
betn 10-15 degrees from fixation in the nasal
retina
47

48. Contd…
• A healthy disc is
normally pink to orange
in color, with well
delineated margins and
a small cup to disc ratio
(<0.3)
48

49. Why the normal disc is pink?
• Thickness and the
cytoarchitecture of fiber
bundles passing
between glial columns
containing capillaries
49

50. Contd…
• Pathologies of the optic nerve, even though
not always detected on ophthalmoscopic
exam, may compromise its function and cause
the following sign;
• Reduced VA
• Afferent pupillary defects
• Visual field defects
• Dischromatopsia(impaired CV)
50

51. Contd…
• Diminished light brightness sensitivity
• Diminished contrast sensitivity
• Optic disc changes on fundoscopy can include
disc edema, hyperemia, paleness and atrophy
• Many a times though the disc looks
completely normal yet it harbors a major
underlying disc
51

52. Congenital anomalies
1. Coloboma
•Defect resulting from malclosure of the fetal
cleft
•Usually inferior and can involve the retina and
choroid
52

53. Optic disc showing coloboma (rt)
53

54. Contd…
2. Hypoplasia
•Smaller disc that carries fewer axon than
normal and may be associated with poor VA,
field defects, strabismus.
•Intake of alcohol, steroids and insulin by
mother during first trimester of pregnancy
increases the risk
54

55. 55

56. Anomalies associated with axial length
and refractive error
• Hyperopes eyes are smaller , disc usually
lacking physiological cup, have crowded
appearance mimicking papilledema
• Myopic discs are larger and surrounded by
white crescent of bare sclera, on the temporal
side ,the CDR is bigger mimicking
glaucomatous cupping
56

57. Myelinated nerve fibre
• Myelinating process which is completed by
the 9th
month of gestation sometimes extends
onto the surface of the disc or surrounding
retina in a radiating fashion causing feathery
patches
• Condition is usually benign
57

58. 58

59. Drusens
• Yellow opalescent hyaline excrescences
derived from calcified axonal debris present
on the surface of the disc or burried in it
• Optic nerve head is full and small mimicking
papilledema
• May be associated with RP
• Autofluoresence before FFA may help in
diagnosis
59

60. 60

61. Optic nerve head swelling
• Common causes
• Congenital: ex drusens
• Systemic diseases: ex; anemia, hypoxemia,
uremia, HTN
• Tumors: ex; hemangiomas, orbital glioma,
meningioma
• Infiltrative diseases: ex; lymphoma
61

62. Severe disc oedema in multiple
sclerosis
62

63. Contd…
• Vascular diseases: ex; AION, giant cell arteritis
and other autoimmune vasculitides, DR
• Ocular diseases: ex; uveitis, hypotony, CRVO
• Inflammatory diseases: optic neuritis, papillitis
and neuroretinitis
• elevated ICP (intracranial pressure) : ex; mass
occupying lesions, pseudotumor cerebri...
63

64. Common causes of optic nerve edema
Papilledema Optic neuritis AION
Non inflammatory edema
secondary to increased ICP
Inflammatory swelling Vascular accident
(occlusion of
short posterior ciliary
artery causing retrolaminar
nerve infarction
Brain tumors , abscesses,
hematomas,
meningitis might be
underlying etiology
Multiple Sclerosis is highly
associated
Hypertension, giant cell
arteritis, hypercoagulable
state are possible factors
Bilateral , may be
asymmetric
Unilateral Unilateral
64

65. Contd…
Papilledema Optic neuritis AION
Headache, nausea,
vomitting
No visual loss usually,
only enlarged blind spot
and possible hyperopia
Retrobulbar pain, especially
on ocular movement, early
central scotoma,
decreased acuity, impaired
color vision,
presence o APD
Acute painless visual loss,
usually hemialtitudinal
defect involving
the lower visual field
Variable degree of disc
swelling, hemorrhages and
cystoid infarcts
Fewer hemorrhages and
cotton wool spots
Pale segmental swelling
and splinter hemorrhages
at its margins
Prognosis usually good if
primary cause of increased
ICP is treated
Vision usually returns to
normal
Poorer prognosis with
permanent . loss. Second
eye is ultimately
involved in one third of
idiopathic cases.
65

66. 66