Download - Optic nerve 1,dr.k.srikanth, 18.5.2016
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Optic Nerve
• Objectives:• Anatomy of the optic Nerve• Physiology of the optic Nerve• Aetiopathogenesis of optic nerve disorders• Inflammations of optic
nerve/diagnosis/treatment• Optic atrophy
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Anatomy
• Consists of approximately-1.2 million neurons• Has Four parts; 1) Intra ocular- 1mm• 2)Intra orbital- 25-30 mm• 3)Intra canalicular-5-9mm• 4) Intra cranial – 10-16
mmmmm• 80% of the fibres arise from the Macula
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Anatomy
• Blood supply;1) Posteror ciliary artey• 2) Peripappillary choroidal
vessels
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physiology
• Axons also take part in the transport of• Mitochondria,chemicals and proteins from the
neuronal cellbody to the distal terminal.• Orthograde (eye to the brain)• Slow component-proteis and enzymes• Intermediate component-mitochondria and• Rapid component- organelles
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Papilledema
• Defined as oedema of the optic discdue to raised intracranial pressure.
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Causes of papilledema
• Bilateral:1) Raised intra cranial pressure• 2)Hypertension• 3) Diabetic papillopathy• 4)Grave’s Disease• 5) Cavernous sinus thrombosis• Unilateral: 1)Optic neuritis• 2)Crvo• 3)Orbital tumours
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Aetiopathogenesis
• 1) Edema• 2)inflammation• 3)Ischemia• 4)Degeneration• 5)Trauma• 6) congenital
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• Patho-physiology :• 1) Due to compression of the centrakl retinal
vein• 2)Blockage of the Axoplasmic flow
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Clinical features
• Ophthalmoscopically;• Disc may be Hyperemic swollen with or
without Haemorrages
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Clinical features
• 1) Transient obscuration of vision• 2)Blurring of Disc Margins• 3) Hyperemia of the Disc• 4) Cup gets filled up• 5)Veins are dilated• 6) Disc appears elevated from the surrounding
Retina
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Clinical features
• 7) Flame shaped Haemorrages on the Disc• 8)Edema with exudation of macula (Macular Fan)• 8) Optic disc pallor in late stages(optic Atrophy)
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Investigations
• 1) Blood pressure – to r/o hypertension• 2) CT scan of Brain- to r/o any space occupying
lesions• 3) Visual fields –to document any field defect• 4) MRI – if CT is normal• 5) Lumbar Puncture – to r/o infection, tumours
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Treatment
• 1 )Reduce intra cranial pressure: • a) Oral Carbonic anhydrase
inhibitor ( Diamox 250 mg TID)• 2) Decompression• 3) specific treatment of the cause
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Differential Diagnosis
• 1)optic Neuritis• 2) Anterior ischemic optic neuropathy• 3) Hypermetropia
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Optic Neuritis
• It is a inflammation of the optic nerve.• Clinically divided into a) Papillitis• b) Neuro retinitis and• c) Retro bulbar neuritis
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Aetiology
• Demyelinating diseases; Multiple sclerosis • Neuro Myelitis optica • Asssociated with infections: Endophthalmitis• Orbital cellulitis• sinusitis• systemic infections• Immune related: Sarcoidosis, Uveitis• Metabolic disorders : Diabetes, Anaemia
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Clinical features
• Sudden drop in vision• Usually unilateral• Accompanied by orbital or retroocular pain• Disturbances of colour vision• Altered perception of moving objects• Worsening of symptoms with excercise
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Clinical features
• Variable degree of vision loss• Decreased colour vision• Relative Afferent Pupillary Defect(Marcus-
Gunn pupil)• Field defects ;a) Relative or Absolute defects in
colour vision b) Central, centero-caecal, Arcuate, Sectorialor Altitudinal
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Field Defects
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Fundus findings
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Papilledema And Optic Neruritis
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Differential Diagnosis
• 1)Ischemic optic neuropathy• 2) Papilledema• 3) Grade 4 Hyper tensive retinopathy• 4) Toxic and Metabolic retinopathy
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Investigations
• Record visual acquity, colour vision• Pupillary light reflex• Dilated retinal examination• Visual fields, VEP• Complete blood count,CRP,Esr,FTA-ABS,ANA• MRI brain
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Treatment
• Treat the primary cause• Guide lines based on ONTT (Optic neuritis
treatment Trial)• IV Methylprednisolone 250mg iv over 30-6-
min repeated 6th hourly for 3 days• Followed by Prednisolone1mg /Kg /day for11
days
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Possible questions• 25 year old female presented with complaints of headache & defective vision. On examination of her fundus,
she had bilateral blurring of the disc margins. What is the differential diagnosis of bilateral disc edema. How would you differentiate
• Papilloedema from papillitis ?• • Classify optic neuritis. Describe the clinical features and management of optic neuritis. • Write the etiology, clinical features and management of papilloedema.• Classify optic atrophy. Describe the features of different types of optic atrophy• Enumerate 4 differential diagnosis for bilateral disc edema• Enumerate 4 differential diagnosis for unilateral disc edema• How would you differentiate• Papilloedema from papillitis ?• What are the field changes in optic neuritis?• What is Marcus Gunn pupil?• Give 2 causes for relative afferent pupillary defect.• Enumerate the features of Horner’s syndrome.• Draw the visual pathway.• Draw the pupillary pathway• Describe the etiology, clinical features and management of AION