Transcript BLOOD SUPPLY OF OPTIC DISC

Dr. DIPALI T. CHAVAN
INTRODUCTION :
 Second cranial & sensory nerve
 Functioning for vision
 Optic nerve head is distal portion of optic nerve
 Synonym – Optic disc, Papilla
 Visualised by ophthalmoscopy
 On visual field – Blind spot
ANATOMY OF OPTIC NERVE HEAD :
 Extent
Extends anteriorly from the retinal surface to
the myelinated portion of the optic nerve that begins
approximately 3 mm just behind the sclera, posterior to
lamina cribrosa
 ONH dimensions
Diameter
Vertical
Horizontal
- 1.88 mm
- 1.77 mm
Area - 0.68 to 4.42 sq.mm
ANATOMY OF OPTIC NERVE HEAD :
ANATOMY OF OPTIC NERVE HEAD :
 Same plane as retina
 Disc is excavated by funnel shape depression called
physiological cup .
It is displaced slightly to temporal side.
It is whiter than rest of disc.
ANATOMY OF OPTIC NERVE HEAD :
Divisions of optic nerve head :
Four portions from anterior to posteriorA. Surface nerve fiber layer
Innermost portion
Contains nerve fibres of retina
astrocytes
B . Prelaminar region
Anterior portion of lamina cribrosa
Contains nerve axons
astrocytes
astroglial tissue
ANATOMY OF OPTIC NERVE HEAD : contd
C. Lamina cribrosa region
Fenestated sheets of scleral connective tissue
Separated by astrocytes.
Fascicles of neurons leave the eye through it
D. Retro laminar region
Characterised by decrese in astrocytes
Acquisition of myline start
ANATOMY OF OPTIC NERVE HEAD : contd
BLOOD SUPPLY OF OPTIC NERVE HEAD
Arterial supply :
 Mainly by posterior cilliary artery except for nerve fiber layer –
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which is supplied by retinal circulation.
Nerve fibre layer is mainly supplied by arterial branches of
central retinal artery.
prelamilar and lamilar region is supplied by posterior cilliary
arteries.
Retrolamilar region supplied by both cilliary and retinal
circulation. Anastomosis between retinal vessels and cilliary
system of vessels does exit.
Arterial anastomosis between 2-4 or more short posterior cilliary
arteries,which lies in sclera around optic nerve called circle of
zinn-haller
Abbreviations: A = arachnoid; C = choroid; CRA = central retinal artery; Col. Br. = Collateral branches; CRV = central
retinal vein; D = dura; LC = lamina cribrosa; NFL = surface nerve fiber layer of the disc; OD = optic disc; ON = optic
nerve; P = pia; PCA = posterior ciliary artery; PR and PLR = prelaminar region; R = retina; RA = retinal arteriole; S =
sclera; SAS = subarachnoid space.
BLOOD SUPPLY OF OPTIC NERVE HEAD contd
BLOOD SUPPLY OF OPTIC NERVE HEAD contd
capillaries:
 Capillaries derived from both retinal and cilliary
circulations.
 Charecteristics include
-tight junctions
-abundent perysites
-nonfenestrated endothelium
 They do not leak fluroscein and support concept of retina
nerve vasculature as a continuous system with CNS
BLOOD SUPPLY OF OPTIC NERVE HEAD contd
Venous drainage:
 Mainly by central retinal vein
 Central retinal vein is tributary of superior ophthalmic
vein ,it wil terminate in cavernous sinus.
 Small portion by choroidal system
Applied anatomy
 Optic nerve head and nerve fibre layer contains
regional ganglion cell axons that are most clearly
associated with glaucomatous vision loss
 the circle of zinn (CZ) was more posteriorly located in
small optic discs. This location may induce risk factors
contributing to the development of ischaemic optic
neuropathy. The combination of small discs, posterior
placement of the CZ, and anatomical variations in the
vascular pattern may predispose to ischaemic events.
Applied anatomy
 there is vascular insufficiency in the ONH in both
anterior ischemic optic neuropathy (AION) and
glaucomatous optic neuropathy (GON)-two major
causes of blindness or of seriously impaired vision in
man. So for the management and prevention of visual
loss in these two disorders, a proper understanding of
the blood flow in the ONH is essential.
 Nocturnal arterial hypotension is imp cause of AION.
Transient nonprfusion or hypopefusion or embolic
lesions of ONH circulation can cause AION.
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