Download - Optic nerve
COLOBOMA OF THE OPTIC DISC results from failure in closure of the
embryonic Fissure
Congenital and developmental disorders1. Anomalies of the optic disc Include crescents, congenital
pigmentation, coloboma, drusen and hypoplasia of the optic disc
2. Anomalies of the nerve fibres Like medullated (opaque) nerve fibres
3. Anomalies of vascular elements such as persistent hyaloid artery,
congenital tortuosity of retinal vessels
MEDULLATED NERVE FIBRES also known as opaque nerve fibres represent myelination of nerve fibres of
the retina Normally medullation of optic nerve
proceeds from brain downwards to the eyeball and stops at the level of lamina cribrosa
PERSISTENT HYALOID ARTERY Congenital remnants of the hyaloid arterial
system persist in different forms Bergmester’s papilla refers to flake
of glial tissue projecting from the optic disc
Vascular loop or a thread of obliterated vessel sometimes is seen running forward into the vitreous
Mittendorf dot represents remnant of the anterior end of hyaloid artery, attached to the posterior lens capsule
OPTIC NEURITIS
includes inflammatory and demyelinating disorders of optic nerve
Etiology◦ Idiopathic.◦ Hereditary optic neuritis (Leber’s disease)◦ Demyelinating disorders multiple sclerosis,
neuromyelitis optica
Parainfectious optic neuritis is associated with measles, mumps, chickenpox, whooping cough and glandular fever
Infectious optic neuritis sinus related (with acute ethmoiditis) or associated with cat scratch fever, syphilis (during primary or secondary stage), lyme disease and cryptococcal meningitis in patients with AIDS
Toxic optic neuritis
Clinical profile Anatomical types. three types: Papillitis. refers to involvement of optic
disc Neuroretinitis refers to combined
involvement of optic disc and surrounding retina in the macular area
Retrobulbar neuritis characterized by involvement of optic nerve behind the eyeball
Symptoms. Asymptomatic or associated with following
symptoms:
Visual loss. Sudden, progressive and profound visual loss is the hallmark
Dark adaptation is lowered
Impairment of colour vision
Episodic transient obscuration of vision
Depth perception is impaired
Pain. mild dull eyeache
Signs are as follows: Visual acuity reduced markedly
Colour vision severely impaired
Pupil shows ill-sustained constriction to light
Marcus Gunn pupil sign
4. Ophthalmoscopic features. hyperaemia of the disc and blurring of
the margins Retinal veins are congested and tortuous Splinter haemorrhages and fine exudates
on the disc inflammatory cells in the vitreous
Retrobulbar neuritis fundus appears normal
Visual field changes. Common relative central or
centrocaecal scotoma Contrast sensitivity is impaired
Visually evoked response (VER) shows reduced amplitude and delay in the transmission time
Differential diagnosis papilloedema and pseudo-papilloedema
Acute retrobulbar neuritis must be differentiated from malingering, hysterical blindness, cortical blindness etc.
Treatment Efforts made to find out and treat the
underlying cause Corticosteroid therapy shorten the period
of visual loss, but will not influence ultimate level of visual recovery in patients with optic neuritis
LEBER’S DISEASE Hereditary optic neuritis affects males around age of 20 years transmitted by the female carriers characterised by progressive visual
failure fundus is initially normal or in the acute
stage disc may be mildly hyperaemic with telangiectatic microangiopathy
Eventually bilateral primary optic atrophy ensues
TOXIC AMBLYOPIAS includes conditions wherein visual loss
results from damage to optic nerve fibres due to effects of exogenous or endogenous poisons
Tobacco amblyopia men who are generally pipe smokers, heavy
drinkers and have a diet deficient in proteins and vitamin B complex
hence also labelled ‘tobacco-alcohol-amblyopia
Pathogenesis
Clinical features. men between 40 and 60 years
characterised by bilateral gradually progressive impairment in central vision
fogginess and difficulty in doing near work
bilateral centrocaecal scotomas
Fundus examination essentially normal or slight temporal pallor of disc
Treatment. complete cessation of tobacco and alcohol
consumption Hydroxycobalamine 1000 μg intramuscular
injections weekly for 10 weeks and care of general health and nutrition
Prognosis. It is good, if complete abstinence from
tobacco and alcohol is maintained Visual recovery is slow and may take
several weeks to months
Methyl alcohol amblyopia results in optic atrophy and permanent
blindness
Pathogenesis. Oxidised into formic acid and formaldehyde They cause oedema followed by
degeneration of the ganglion cells of the retina, resulting in complete blindness due to optic atrophy
Clinical features. Headache, dizziness, nausea, vomiting,
abdominal pain, delirium, stupor and even death
characteristic odour due to excretion of formaldehyde in the breath or sweat is a helpful diagnostic sign
Ocular features. Patients are usually brought with almost
complete blindness, which is noticed after 2-3 days, when stupor weans off.
Fundus examination in early cases mild disc oedema and markedly narrowed blood vessels,
Finally bilateral primary optic atrophy
Treatment 1. Gastric lavage
2. Administration of alkali Soda bicarb given orally or intravenously (500 ml of 5% solution)
3. Ethyl alcohol. given in early stages. Is given in small frequent doses, 90 cc every 3 hours for 3 days
4. Eliminative treatment by diaphoresis in the form of peritoneal dialysis
5. Prognosis is usually poor; death may occur due to acute poisoning.
Blindness occurs in those who survive
Quinine amblyopia Clinical features. near total blindness
Deafness and tinnitus may be associated
pupils fixed and dilated
Fundus examination retinal oedema, marked pallor of the disc and extreme attenuation of retinal vessels
Visual fields markedly contracted
Ethambutol amblyopia Antitubercular drug toxicity usually occurs in patients who have
associated alcoholism and diabetes
Clinical features. optic neuritis with typical central scotoma Optic chiasma bitemporal hemianopia reduced vision & colour vision during
antitubercular treatment Fundus examination papillitis Recovery occurs following cessation
ANTERIOR ISCHAEMIC OPTIC NEUROPATHY
(AION) refers to segmental or generalised
infarction of anterior part of optic nerveEtiology. results from occlusion of short
posterior ciliary arteries Depending upon etiology it may be typified
as follows: Idiopathic AION.
Arteritic AION. occurs in association with giant cell arteritis
AION due to other causes. associated with severe anaemia, collagen
vascular disorders, following massive haemorrhage, papilloedema, migraine and malignant hypertension
Clinical features. Visual loss is usually marked and sudden Fundus examination during acute stage
reveal segmental or diffuse oedematous, pale or hyperaemic disc, usually associated with splinter haemorrhages
Visual fields altitudinal hemianopia
Treatment. Immediate treatment heavy doses of
corticosteroids (80 mg prednisolone daily) and tapered by 10 mg weekly
Steroids in small doses (5 mg prednisolone) continued for a long time (3 months to one year)
PAPILLOEDEMA ‘papilloedema’ passive disc swelling
associated with increased intracranial pressure which is almost always bilateral although it may be asymmetrical
‘disc oedema or disc swelling’ includes all causes of active or passive oedematous swelling of the optic disc
Causes of disc oedema1. Congenital anomalous elevation
(Pseudopapilloedema)
2. Inflammations Papillitis Neuroretinitis
3. Ocular diseases Uveitis Hypotony Vein occlusion
4. Orbital causes Tumours Graves’ orbitopathy Orbital cellulitis
5. Vascular causes Anaemia Uremia Anterior ischaemic optic neuropathy
6. Increased intracranial pressure
Etiopathogenesis of papilloedema Causes. secondary to raised intracranial pressure
which may be associated with following conditions:
Congenital conditions aqueductal stenosis and craniosynostosis
Intracranial space-occupying lesions (ICSOLs).
Intracranial infections such as meningitis and encephalitis
Intracranial haemorrhages.
Obstruction of CSF absorption via arachnoid villi which have been damaged previously
Tumours of spinal cord
Idiopathic intracranial hypertension (IIH)
Systemic conditions malignant hypertension, pregnancy induced hypertension (PIH) cardiopulmonary insufficiency, blood dyscrasias and nephritis
Diffuse cerebral oedema from blunt head trauma
swelling due to ocular and orbital lesions is usually unilateral
In majority of the cases with raised intracranial pressure, papilloedema is bilateral
1. Foster-Kennedy syndrome associated with olfactory or sphenoidal
meningiomata and frontal lobe tumours There occurs pressure optic atrophy on side
of lesion and papilloedema on other side (due to raised intracranial pressure)
Pseudo-Foster-Kennedy syndrome characterised by occurrence of unilateral
papilloedema with raised intracranial pressure (due to any cause) and a pre-existing optic atrophy (due to any cause) on other side
Pathogenesis. It has been a confused and
controversial issue
Hayreh’s theory is the most accepted one
states that develops as a result of stasis of axoplasm in the prelaminar region of optic disc, due to an alteration in the pressure gradient across the lamina cribrosa
Clinical features [A] General features. headache, nausea, projectile vomiting and
diplopia Focal neurological deficit
[B] Ocular features. history of recurrent attacks of transient
blackout of vision (amaurosis fugax) Visual acuity and pupillary reactions : normal Clinical features described under four
stages: early, fully developed, chronic and atrophic
1. Early (incipient) papilloedema Symptoms usually absent and visual acuity
normal Pupillary reactions normal Ophthalmoscopic features Obscuration of disc margins Absence of spontaneous venous pulsation
at the disc (appreciated in 80% of the normal individuals)
Mild hyperaemia of disc Splinter haemorrhages. Visual fields are fairly normal.
2. Established (fully developed) papilloedema
Symptoms. history of transient visual obscurations in
one or both eyes, lasting a few seconds, after standing
Visual acuity is usually normal, Pupillary reaction remain normal
Ophthalmoscopic features Apparent optic disc oedema is seen as its
forward elevation above the plane of retina
Physiological cup of the optic disc is obliterated.
Disc becomes hyperaemic and blurring of the margin is present all-around
Multiple soft exudates and superficial haemorrhages may be seen near the disc
Veins becomes tortuous and engorged Visual fields enlargement of blind spot
3. Chronic or long standing (vintage) papilloedema
Symptoms. Visual acuity is reduced ???? Pupillary reactions normal Ophthalmoscopic features acute haemorrhages and exudates resolve,
and peripapillary oedema is resorbed Optic disc gives appearance of the dome of
a champagne cork The central cup remains obliterated Visual fields Blind spot is enlarged and
the visual fields begin to constrict
4. Atrophic papilloedema Symptoms. develops after 6-9 months of chronic
papilloedema Severely impaired visual acuity Pupillary reaction. impaired
Ophthalmoscopic features greyish white discoloration and pallor of
the disc due to atrophy of the neurons and associated gliosis
Prominence of the disc decreases Retinal arterioles are narrowed Whitish sheathing develops around the
vessels. Visual fields Concentric contraction of
peripheral fields
Treatment and prognosis neurological emergency and requires
immediate hospitalisation
As a rule unless causative disease is treatable or cerebral decompression is done, the course of papilloedema is chronic and ultimate visual prognosis is bad
OPTIC ATROPHY refers to degeneration of the optic nerve occurs as an end result of any pathologic
process that damages axons
Classification Primary optic atrophy refers to simple
degeneration of the nerve fibres without any complicating process within the eye e.g., syphilitic optic atrophy.
Secondary optic atrophy occurs following any pathologic process which produces optic neuritis or papilloedema
Ophthalmoscopic classification. It is more useful
Common types are as follows: Primary (simple) optic atrophy Consecutive optic atrophy Glaucomatous optic atrophy Post-neuritic optic atrophy Vascular (ischaemic) optic atrophy
Ascending versus descending optic atrophy.
Ascending optic atrophy follows damage to ganglion cells or nerve fibre layer due to disease of the retina or optic disc
Descending or retrograde optic atrophy proceeds from the region of the optic tract, chiasma or posterior portion of the optic nerve towards the optic disc
Etiology 1. Primary (simple) optic atrophy. multiple sclerosis, retrobulbar neuritis
(idiopathic), Leber’s and other hereditary optic atrophies
2. Consecutive optic atrophy. occurs following destruction of ganglion
cells secondary to degenerative or inflammatory lesions of the choroid and/or retina
Its common causes are: diffuse chorioretinitis, retinitis pigmentosa,
pathological myopia and occlusion of central retinal artery
3. Postneuritic optic atrophy. It develops as a sequelae to long-standing papilloedema or papillitis
4. Glaucomatous optic atrophy. It results from the effect of long standing raised intraocular pressure
5. Vascular (ischaemic) optic atrophy. It results from the conditions (other than glaucoma) producing disc ischaemia
include: giant cell arteritis, severe haemorrhage, severe anaemia and quinine poisoning
Clinical features of optic atrophy 1. Loss of vision, may be of sudden or
gradual onset
2. Pupil is semidilated and direct light reflex is very sluggish or absent
Swinging flash light test depicts Marcus Gunn pupil
3. Visual field loss will vary with the distribution of the fibres that have been damaged
4. Ophthalmoscopic appearance of the disc will vary with the type of optic atrophy.
In general pallor of the disc and decrease in the number of small blood vessels (Kastenbaum index)
Ophthalmoscopic features of different types of optic atrophy are as described below:
Primary optic atrophy
Consecutive optic
atrophy
Post-neuritic optic atrophy
Glaucomatous optic atrophy
Ischaemic optic atrophy
chalky white or white with bluish hue
Disc appears yellow waxy
Optic disc looks dirty white in colour
Pale disc pallor of the optic disc
edges (margins) are sharply outlined
edges are not so sharply defined
edges are blurred,.
Edges well defined
Lamina cribrosa is clearly seen at the bottom of the physiological cup
physiological cup is obliterated and lamina cribrosa is not visible
deep and wide cupping of the optic disc and nasal shift of the blood vessels
Major retinal vessels and surrounding retina are normal
Retinal vessels are attenuated
vessels are attenuated and perivascular sheathing is often present
Normal attenuation of the vessels
Differential diagnosis 1. Non-pathological pallor of optic disc is
seen in: axial myopia, infants, and elderly people
sclerotic changes physiological
2. Pathological causes of pallor disc (other than
optic atrophy) include: hypoplasia, congenital pit,and coloboma
Treatment The underlying cause when treated help in
preserving some vision in patients with partial optic atrophy
once complete atrophy has set in, the vision cannot be recovered