Download - Optic nerve 1,dr.k.srikanth, 18.5.2016
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
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
Anatomy
• Blood supply;1) Posteror ciliary artey• 2) Peripappillary choroidal
vessels
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
Papilledema
• Defined as oedema of the optic discdue to raised intracranial pressure.
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
Aetiopathogenesis
• 1) Edema• 2)inflammation• 3)Ischemia• 4)Degeneration• 5)Trauma• 6) congenital
• Patho-physiology :• 1) Due to compression of the centrakl retinal
vein• 2)Blockage of the Axoplasmic flow
Clinical features
• Ophthalmoscopically;• Disc may be Hyperemic swollen with or
without Haemorrages
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
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)
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
Treatment
• 1 )Reduce intra cranial pressure: • a) Oral Carbonic anhydrase
inhibitor ( Diamox 250 mg TID)• 2) Decompression• 3) specific treatment of the cause
Differential Diagnosis
• 1)optic Neuritis• 2) Anterior ischemic optic neuropathy• 3) Hypermetropia
Optic Neuritis
• It is a inflammation of the optic nerve.• Clinically divided into a) Papillitis• b) Neuro retinitis and• c) Retro bulbar neuritis
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
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
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
Field Defects
Fundus findings
Papilledema And Optic Neruritis
Differential Diagnosis
• 1)Ischemic optic neuropathy• 2) Papilledema• 3) Grade 4 Hyper tensive retinopathy• 4) Toxic and Metabolic retinopathy
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
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
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