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