optic nerve 1,dr.k.srikanth, 18.5.2016

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Optic Nerve

Optic NerveObjectives:Anatomy of the optic NervePhysiology of the optic NerveAetiopathogenesis of optic nerve disordersInflammations of optic nerve/diagnosis/treatmentOptic atrophy

AnatomyConsists of approximately-1.2 million neuronsHas Four parts; 1) Intra ocular- 1mm 2)Intra orbital- 25-30 mm 3)Intra canalicular-5-9mm 4) Intra cranial 10-16 mmmmm80% of the fibres arise from the Macula

AnatomyBlood supply;1) Posteror ciliary artey 2) Peripappillary choroidal vessels

physiologyAxons also take part in the transport ofMitochondria,chemicals and proteins from the neuronal cellbody to the distal terminal.Orthograde (eye to the brain)Slow component-proteis and enzymesIntermediate component-mitochondria andRapid component- organelles

PapilledemaDefined as oedema of the optic discdue to raised intracranial pressure.

Causes of papilledemaBilateral:1) Raised intra cranial pressure 2)Hypertension 3) Diabetic papillopathy 4)Graves Disease 5) Cavernous sinus thrombosisUnilateral: 1)Optic neuritis 2)Crvo 3)Orbital tumours

Aetiopathogenesis1) Edema2)inflammation3)Ischemia4)Degeneration5)Trauma6) congenital

Patho-physiology :1) Due to compression of the centrakl retinal vein2)Blockage of the Axoplasmic flow

Clinical featuresOphthalmoscopically;Disc may be Hyperemic swollen with or without Haemorrages

Clinical features1) Transient obscuration of vision2)Blurring of Disc Margins3) Hyperemia of the Disc4) Cup gets filled up5)Veins are dilated6) Disc appears elevated from the surrounding Retina

Clinical features7) Flame shaped Haemorrages on the Disc8)Edema with exudation of macula (Macular Fan)8) Optic disc pallor in late stages(optic Atrophy)

Investigations 1) Blood pressure to r/o hypertension2) CT scan of Brain- to r/o any space occupying lesions3) Visual fields to document any field defect4) MRI if CT is normal5) Lumbar Puncture to r/o infection, tumours

Treatment1 )Reduce intra cranial pressure: a) Oral Carbonic anhydrase inhibitor ( Diamox 250 mg TID)2) Decompression3) specific treatment of the cause

Differential Diagnosis1)optic Neuritis2) Anterior ischemic optic neuropathy3) Hypermetropia

Optic NeuritisIt is a inflammation of the optic nerve.Clinically divided into a) Papillitis b) Neuro retinitis and c) Retro bulbar neuritis

AetiologyDemyelinating diseases; Multiple sclerosis Neuro Myelitis optica Asssociated with infections: Endophthalmitis Orbital cellulitis sinusitis systemic infectionsImmune related: Sarcoidosis, UveitisMetabolic disorders : Diabetes, Anaemia

Clinical featuresSudden drop in visionUsually unilateralAccompanied by orbital or retroocular painDisturbances of colour visionAltered perception of moving objectsWorsening of symptoms with excercise

Clinical featuresVariable degree of vision lossDecreased colour visionRelative 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 Diagnosis1)Ischemic optic neuropathy2) Papilledema3) Grade 4 Hyper tensive retinopathy4) Toxic and Metabolic retinopathy

InvestigationsRecord visual acquity, colour visionPupillary light reflexDilated retinal examinationVisual fields, VEPComplete blood count,CRP,Esr,FTA-ABS,ANAMRI brain

TreatmentTreat the primary causeGuide lines based on ONTT (Optic neuritis treatment Trial)IV Methylprednisolone 250mg iv over 30-6- min repeated 6th hourly for 3 daysFollowed by Prednisolone1mg /Kg /day for11 days

Possible questions25 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 differentiatePapilloedema 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 atrophyEnumerate 4 differential diagnosis for bilateral disc edemaEnumerate 4 differential diagnosis for unilateral disc edemaHow would you differentiatePapilloedema 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 Horners syndrome.Draw the visual pathway.Draw the pupillary pathwayDescribe the etiology, clinical features and management of AION

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