2. THE NORMAL OPTIC DISC
Intraocular part of the optic nerve marking the radial convergence of fibres
from neural retina and their point of exit from the eye
Circular or slightly ovoid, 1.5mm in diameter
4mm nasal and 1mm superior to the centre of the fovea
Shape, colour, size, margins of disc, retinal vessels, size and colour of
physiological cup, colour of NRR
Outer, yellow-pink rim – conv of ON fibres and turning away at right
angles from the retina
Central, deep, pale cup – mostly astrocytes and connective tissue
3. Central Retinal Vessels divide dichotomously within the cup and on the
disc to 4 branches
Veins lie temporal to arteries
Spontaneous venous pulsation – N, absent in 20% of normal
Arterial pulsations- always pathological, in glaucoma or aortic
incompetence
4. MORPHOLOGY OF ON HEAD
3 LAYERS-
1) surface layer- non myelinated nerve fibres from ganglion
cells converging at OD rim
2) prelaminar layer- axons turn at right angles towards globe exit.
Astroglial cells divide nerve fibre into fascicles
3) laminar layer- nerve fibre bundles pass through fenestrations in
the lamina cribrosa (crib. plate)
5. Number of ON fibres mostly constant.
Smaller disc has smaller cup due to confluence of nerve fibres
CDR – wide variability, 0.2-0.4 measured along vertical axis
Larger discs have larger and deeper cups
Assymetry of CDR >0.2 – risk of glaucoma
6. OD margins- well defined usually with no discontinuity between disc margin and
adjacent RPE and choroid
In oblique insertion of ON into globe and consequent tilting of disc, RPE and choroid
may fail to reach disc margin.
Gap in RPE revealing underlying choroid – dark juxtapapillary choroidal crescent
(choroidal ring, if complete)
RPE and choroid both deficient – juxtapapillary scleral crescent (myopia)
Mostly temporal in location
Pigment crescent d/t RPE thickening seen nasally
7. GENESIS
7th week of IUL- fusion of lips of embryonic fissure (colobomas, tilted disc)
Cellular differentiation of retina at 5th -6th week. Abnormal differentiation of neural and
pigment epithelial cells at the cup-stalk junction causes optic pit formation
Around 8 wks, nerve processes converge at the junction between optic cup and optic
stalk.(optic nerve hypoplasia or aplasia)
8. Neuroectodermal cells invaginate into optic stalk during closure of embryonic
fissure giving rise to neuroglial supporting tissue. Invading mesenchymal cells
with nerve tissue contribute in optic nerve formation. (excess non neural tissue
causes megalopapilla)
Longitudinal septa within the ON is formed by glial tissue augmented by the
lamina cribrosa. (displacement of LC-morning glory anomaly)
Myelination of ON fibres initiated by oligodendrocytes at 6th month and
completed till lamina cribrosa by term. Presence of oligodendrocytes anterior
to disc causes atypical myelination post term (MNF)
9. OPTIC DISC COLOBOMA
Pathogenesis: incomplete or abnormal apposition of the proximal ends of
the embryonic fissure
B/L mostly, AD or sporadic
Enlarged or excavated disc, deepest part present inferiorly, NRR maybe
absent inferiorly, OD loses its integrity inferiorly
The CRV branches over the disk earlier than normally because of loss of
architecture , hence more vessels cross the inferior border.
Maybe isolated or along with retinochoroidal coloboma
Degree of foveal involvement by the coloboma decides prognosis
10. Optic nerve colobomas may be associated with the following
Microphthalmos
Iris coloboma, and RC coloboma
Serous macular detachment (Poor prognostic factor)- rhegmatogenous
a/w RC coloboma
non-rhegmatogenous when a/w isolated disc coloboma
Systemic associations like :
CHARGE syndrome (coloboma, heart anomaly, choanal atresia, retardation,
genital and ear anomalies)
Walker- Warburg syndrome
Goldenhar’s syndrome
ASSOCIATIONS
11. OPTIC NERVE HYPOPLASIA
One of the most common disc anomalies
RFs- maternal smoking & diabetes, preterm birth, anticonvulsants during
pregnancy
Absence or reduction in number of nerve fibres with normal mesodermal
element in ganglion cell layer
Maybe linked with anencephaly and other cranial maldevelopments
incompatible with life
Vision variably affected, non progressive, VF defects also variable
a/w Strabismus, amblyopia, microophthalmos, nystagmus
Growth Hormone required by 3-4yrs if a/w absence of pituitary
infundibulum
12. 1) Isolated ONH- MRI shows reduction in diameter of disc.
2) Septo-optic dysplasia (de Morsier syndrome) constellation of ONH, absence of
the septum pellucidum, and partial or complete agenesis of the corpus callosum.
Double-ring sign:
yellowish peripapillary ring of sclera and an
outer concentric ring of hypopigmentation.
outer ring of normal junction between sclera
and lamina cribrosa
inner ring denoting extension of retina and
RPE over lamina cribrosa
13. MEGALOPAPILLA
Abnormally large optic nerve head d/t increase
in either neural supporting tissue or
mesodermal tissue infiltrating the nerve
If a/w midline defects of face and skull,
radiological inv to rule out basal or spheno-
ethmoidal encephalocele
Vision mostly normal, enlarged blind spot
maybe seen
14. TILTED DISC / FUCH’S COLOBOMA
1-2% of population
75% B/L , non-hereditary, considered to be a type of coloboma, mostly
inferonasal tilting is seen
ON enters globe at an unusual angle, causing elevation of superotemporal
part of disc and posterior displacement of inferonasal part
Optic disc oval with its long axis obliquely oriented
Dysversion of the optic cup and retinal vessel displacement i.e. situs
inversus
accompanied by thinning of the inferonasal RPE and choroid, and
myopic astigmatism
15. Greater the disc tilting, more is the visual impairment
Non-progressive Bitemporal Hemianopia in the superotemporal quadrants
which donot respect the vertical meridians, mostly medium isopters affected
D/d: suprasellar chiasmal tumors
Refractive correction has a high chance of correcting these VF defects unless
associated ectasia is present
16. MORNING GLORY OPTIC DISC
U/L, Sporadic, F>M, rare
Physiologic optic cup replaced by excavated funnel shaped depression in
disc, with a central core of glial tissue, a pigmented juxtapapillary annulus,
retinal vessels looping like straight radial spokes over the rim
3 suggested theories-
Central colobomatous defect
ONH prolapse and posterior displacement of the lamina cribrosa d/t
enlarged scleral foramen
a/w PHPV
17. Vision low from birth
Mostly presents alone, rarely part of multisystemic diseases
Maybe a/w basal encephalocoele, characteristic facial features like
hypertelorism,cleft palate, upper lid notch, broad widened nasal bridge, iris
and RC colobomas, absence of corpus callosum
18. MYELINATED NERVE FIBRES
Seen in 1% population, asymptomatic , not present at birth, appears later
White highly reflective opaque fan shaped lesions with feathery margins obscuring underlying
vessels, may or maynot extend from the optic disc
No other associated features
Large MNF may show small VF defects
19. OPTIC DISC PIT
85% U/L,usually single, frequently temporal , never involves disc margin
Cavitation formed by the herniation of dysplastic retina into a collagen-lined pocket
extending posteriorly through a defect in the lamina cribrosa
Round or oval greyish depression in ONH
50-65% cases a/w serous macular detachment causing d/v
Age of serous detachment 25-45yrs
VF defect in form of paracentral arcuate scotoma
20. ANATOMY OF OPTIC PIT
The herniated dysplastic tissue and pit
capsule vary in permeability from one
eye to another. In eyes with an
impermeable capsule, the pit functions
like a bulb syringe, ‘‘sucking’’ vitreous
fluid into the pit sac during a drop in
intracranial pressure (ICP), and then,
During a rise in pressure, expelling it
from the sac.
In eyes with a permeable capsule,
fluctuations in ICP are transmitted to
the pit by CSF migration across the
capsule.
NEIRAJ JAIN & MARK JOHNSON,2014
21. Fluid from optic pit initially produces an inner layer retinal separation (retinoschisis) that overlies
posterior pole which then develops outer macular hole and leads to serous macular detachment
Postulated source of the fluid could be-
1) cerebrospinal fluid (CSF),
2) liquefied vitreous entering through the pit or through a macular hole, and
3) leakage from either choroidal vessels or permeable vessels in the pit.
Long standing serous MD can lead to macular hole formation as a part of its natural
course
22. TREATMENT
OBSERVATION- Spontaneous resolution in <25% (Sobol WM et al, 1997)
LASER PHOTOCOAGULATION- Laser at the margins of the OD pit to form chorioretinal
adhesions to limit the detachment has been proved to be ineffective in most cases. Also,
repeated lasers were required . ( Gass JDM ,1992)
GAS TAMPONADE WITH LASER PHOTOCOAGULATION- Pneumatic displacement of the outer
layer detachment, improves central vision. Did not Have great results.
MACULAR SCLERAL BUCKLING( Theodossiadis, 2001)- In 25 of 26 patients, permanent closure
of the connection between the optic disk pit and the intraretinal schisis was demonstrated.
Eventual disappearance of schisis and subretinal fluid was depicted.
23. Vitrectomy with ILM peeling , laser photocoagulation and gas tamponade-
Dhananjaya Shukla et al,2012 – 5 of 7 pts achieved BCVA of >20/30
Significant controversy as to whether vitreomacular traction has a role in
macular schisis in optic pit.(Neiraj Jain & Mark Johnson, 2014)
PPV with complete PVD induction with Gas Tamponade-
No laser done. PVD induction to remove all source of vitreoretinal traction
which is considered a cause of serous detachment in such cases. (Akito et al. in
2005 )
10 of 11 cases operated obtained 6/6 vision over 1 yr of followup
24. Long-term Results of Vitrectomy without
Laser Treatment for Macular Detachment
Associated with an Optic Disc Pit
Akito Hirakata, MD, Annabelle A. Okada, MD, Tetsuo Hida, MD
Optical coherencetomography at presentation revealed
an inner layer separation as well as a hole in the outer
layer detachment at the macula and an outer layer
detachment surrounding the hole.
3 months after vitrectomy and gas tamponade, OCT
showed a decrease in the inner layer separation and outer
layer detachment.
At 9 months, OCT showed resolution of the inner layer
separation but a residual outer layer detachment.
Fundus photograph and OCT at 12 months
postoperatively showing the macula completely
reattached and the optic disc pit appearing grayer and
deeper than preoperatively.
Visual acuity was 1.
25. CONCLUSION
Most congenital optic disc anomalies are non progressive and untreatable
Accurate diagnosis is however essential to distinguish them from other
progressive ocular disorders which may be amenable to treatment
In addition, some of them are associated it systemic abnormalities which
may have serious implications for the patient if not diagnosed in time.
