Diseases of the Optic Nerve 09

8/8/2019 Diseases of the Optic Nerve 09

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DISEASES OF THEDISEASES OF THEOPTIC NERVEOPTIC NERVE


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DISEASES OF THE OPTIC NERVEDISEASES OF THE OPTIC NERVE

TheThe visualvisual pathwaypathway startingstarting fromfromretinaretina consistsconsists of of opticoptic nerves,nerves,opticoptic chiasma,chiasma, opticoptic tracts,tracts,laterallateral geniculategeniculate bodies,bodies, opticopticradiationsradiations andand visualvisual cortexcortex..

EachEach opticoptic nervenerve startsstarts fromfrom thetheopticoptic discdisc andand extendsextends upup totoopticoptic chiasma,chiasma, wherewhere thethe twotwonervesnerves meetmeet. . TheThe opticoptic nervenerve isisaboutabout 4545--5050 mmmm inin length,length, andandcancan bebe divideddivided intointo 44 partsparts::intraocular intraocular ( (11 mm),mm), intraorbitalintraorbital((3030 mm),mm), intracanalicular intracanalicular ( (66--99mm)mm) andand intracranialintracranial ( (1010 mm)mm)..


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TheThe opticoptic nervenerve headhead isis thethe exitexit sitesite for for allall retinalretinalnervenerve fibresfibres.. TheThe papillomacular papillomacular bundlebundle containscontainsthethe smallsmall--calibrecalibre nervenerve fibresfibres whichwhich subservesubservethethe conecone systemsystem of of thethe foveafovea. . OpticOptic nervenervelesionslesions havehave aa predilectionpredilection for for suppressingsuppressing thethefunctionfunction of of thisthis importantimportant anatomicalanatomical structurestructureandand causecause thethe followingfollowing clinicalclinical signssigns: :11.. DiminishedDiminished visualvisual acuityacuity22.. VariousVarious typestypes of of visualvisual fieldfield defectsdefects

33.. DiminishedDiminished pupillarypupillary lightlight reactionsreactions44.. ImpairmentImpairment of of colour colour visionvision


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Optic neuritisOptic neuritisOptic neuritisOptic neuritis is anis aninflammatory or inflammatory or demyelinatingdemyelinatingdisorder of the opticdisorder of the opticnerve. Onnerve. Onophthalmoscopy itophthalmoscopy itcan be divided intocan be divided intotwo types:two types:1. Retrobulbar 1. Retrobulbar neuritisneuritis, , 2. Papillitis2. Papillitis


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Etiology Etiology 11.. IdiopathicIdiopathic: : inin aa largelarge proportionproportion of of casescases thetheunderlyingunderlying causecause inin unidentifiableunidentifiable22.. MultipleMultiple sclerosissclerosis - - itit isis thethe commonestcommonest causecauseof of monosymptomaticmonosymptomatic acuteacute idiopathicidiopathic opticopticneuritisneuritis

33.. InflammatoryInflammatory disordersdisorders of of thethe brainbrain andand itsitssheathssheaths (meningitis(meningitis andand encephalitis)encephalitis)44.. InflammatoryInflammatory disordersdisorders of of thethe eyeeye andand orbitorbit55.. InflammatoryInflammatory disordersdisorders of of thethe paranasalparanasalsinusessinuses66.. Acute Acute andand chronicchronic inflammationsinflammations (viral,(viral,bacterialbacterial inin origin)origin)77.. ToxicToxic opticoptic neuritisneuritis


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Pap illitisPap illitis -- it is inflammation of the optic disc (opticit is inflammation of the optic disc (opticnerve head). This condition is usually unilateral.nerve head). This condition is usually unilateral.

C linic a l fe a tures C linic a l fe a tures PresentationPresentation - - sudden,sudden,progressive and profoundprogressive and profoundvisual loss is the hallmarkvisual loss is the hallmarkof papillitis. May beof papillitis. May bedefects of visual field,defects of visual field,impairment of colour impairment of colour vision, dark adaptationvision, dark adaptationmay also be lowered. Themay also be lowered. Themost common field defectmost common field defectis a relative central or is a relative central or centrocaecal scotoma.centrocaecal scotoma.


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C linic a l fe a turesC linic a l fe a tures

Visual acuity is usually reducedVisual acuity is usually reducedmarkedly. Opthalmoscopy ismarkedly. Opthalmoscopy ischaracterized by hyperaemia of characterized by hyperaemia of the disc and blurring of thethe disc and blurring of themargins. Disc becomesmargins. Disc becomesoedematous. Retinal veins areoedematous. Retinal veins arecongested and tortuous. In somecongested and tortuous. In somecases there may also becases there may also behaemorrhages on and aroundhaemorrhages on and aroundthe optic disc. Slitthe optic disc. Slit- -lamplampexaminatoion may revealexaminatoion may revealinflammatory cells in the vitreousinflammatory cells in the vitreousbody.body.


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C linic a l fe a turesC linic a l fe a tures

PapillitisPapillitis shouldshould bebe differentiated differentiated fromfrompapilloedemapapilloedema andand pseudoneuritispseudoneuritis. . InIn

severesevere casescases of of papillitispapillitissecondarysecondary atrophyatrophy of of thethe opticoptic nervenerveoccursoccurs. .


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R etrobulb a r neuritisR etrobulb a r neuritisR etrobulb a r neuritisR etrobulb a r neuritis -- ititis an inflammation of theis an inflammation of theoptic nerve situatedoptic nerve situatedbehind the eyeball. It isbehind the eyeball. It is

characterized by a normalcharacterized by a normaloptic nerve head andoptic nerve head andretinal nerve fibre layer.retinal nerve fibre layer.This is the most commonThis is the most commontype in adults and istype in adults and isfrequently associated withfrequently associated withdemyelinatin.demyelinatin.


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R etrobulb a r neuritisR etrobulb a r neuritis

ItsIts cl ini c a l cl ini c a l featuresfeatures (except(exceptthethe fundusfundus changes)changes) areareessentiallyessentially similar similar toto thatthat of of thethe papillitispapillitis.. TheyThey areare::diminisheddiminished visualvisual acuityacuity (of (of differentdifferent degree),degree),generalizedgeneralized constrictionconstriction of of

thethe visualvisual fieldfield bordersborders(especially(especially onon redred andandgreengreen colour),colour), centralcentralscotomascotoma. .


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R etrobulb a r neuritisR etrobulb a r neuritisRetrobulbar Retrobulbar neuritisneuritis maymay bebe acuteacute andand chronicchronic. .ChronicChronic retrobulbar retrobulbar neuritisneuritis isis alsoalso knownknown asastoxictoxic amblyopiaamblyopia. .ReccurentReccurent attackattack of of acuteacute retrobulbar retrobulbar neuritisneuritisareare followedfollowed byby primaryprimary opticoptic atrophyatrophy. .P rognosisP rognosis: : aboutabout 7575%% casescases withwith mildmild coursecoursegetget goodgood visualvisual recoveryrecovery. . RecoveryRecovery takestakesusuallyusually 44--66 weeksweeks. . However,However, despitedespite returnreturn of of visualvisual acuityacuity other other parametersparameters of of visualvisual functionfunction(colour (colour vision,vision, contrastcontrast sensivity)sensivity) oftenoften remainremainabnormalabnormal. . SometimesSometimes opticoptic nervenerve atrophyatrophy maymaydevelopsdevelops. .


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T re a tment T re a tment 11.. CorticosteroidsCorticosteroids (systemically(systemically or or byby retrobulbar retrobulbar injection)injection)22.. Antibiotics Antibiotics 33.. VitaminsVitamins C,C, Bi,Bi, BB66,, BiBi22 (after (after acuteacuteattack)attack)44.. DehydrationDehydration andand desintoxycationdesintoxycation 5 5.. EtiologicalEtiologicaltreatmenttreatment66.. NonsteroidNonsteroid antianti--inflammatoryinflammatory agentsagents 7 7.. VasodilatorsVasodilatorsMethylMethyl alcoholalcohol amblyopiaamblyopia isis typicallytypically acute,acute, usuallyusuallyresultingresulting inin opticoptic nervenerve atrophyatrophy andand permanentpermanentblindnessblindness. . ItIt usuallyusually occursoccurs duedue toto intakeintake of of woodwoodalcoholalcohol. . ToxicToxic agentsagents causecause oedemaoedema followedfollowed bybydegenerationdegeneration of of thethe ganglionganglion cellscells of of thethe retina,retina, resultingresulting

inin completecomplete blindnessblindness duedue toto opticoptic atrophyatrophy. .ClinicalClinical featuresfeatures consistconsist of of generalgeneral symptomssymptoms of of acuteacutepoisoningpoisoning andand ocular ocular featuresfeatures (which(which includeinclude signssigns of of retrobulbar retrobulbar neuritisneuritis withwith mildmild discdisc oedemaoedema andand markedlymarkedlynarrowednarrowed bloodblood vessels)vessels). .


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PapilloedemaPapilloedema

PapilloedemaPapilloedema isis defineddefinedas swelling of the opticas swelling of the opticnerve head secondary tonerve head secondary toraised intracranialraised intracranial

pressure.pressure. RaisedRaisedintracranial pressure mayintracranial pressure maytherefore be caused bytherefore be caused bythe following mechanisms:the following mechanisms:

11.. SpaceSpace- -occupyingoccupying lesionslesions(including(including intracranialintracranialhaemorrhage,haemorrhage, brainbraintumours,tumours, abscess)abscess)


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PapilloedemaPapilloedema22.. BlockageBlockage of of thethe ventricular ventricular

systemsystem byby congenitalcongenital or or aquiredaquired lesionslesions33.. ObstructionObstruction of of cerebrospinalcerebrospinal

fluidfluid (as(as thethe resultresult of of

meningitis,meningitis, cerebralcerebral trauma)trauma)44.. BenignBenign intracranialintracranial

hypertensionhypertension (pseudotumour (pseudotumour cerebri)cerebri)

55.. SevereSevere hypertensionhypertension66.. HypersecretionHypersecretion of of

cerebrospinalcerebrospinal fluidfluid byby choroidchoroidplexusplexus tumour tumour (rare)(rare)


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TheThe preciseprecise pathgenesispathgenesis of of papilloedemapapilloedema is is notnotentirelyentirely understood,understood, butbut itit seemsseems clear clear thatthat intraintra--axonalaxonal swellingswelling withwith accumulationaccumulation of of mitochondriamitochondriaandand notnot extracellular extracellular extravasationextravasation of of fluidfluid isis thetheprincipalprincipal earlyearly mechanismmechanism resultingresulting fromfrom raisedraisedintraneuralintraneural pressurepressure. . ThisThis resultsresults inin swellingswelling of of prelaminar prelaminar nervenerve axonsaxons andand earlyearly papilloedemapapilloedema is issimplysimply thethe resultresult of of axoplasmicaxoplasmic stasisstasis atat thethe nervenervediscdisc.. TheThe vascular vascular changes,changes, i i..ee..,, hyperaemia,hyperaemia,

venousvenous congestion,congestion, andand haemorrhage,haemorrhage, arearesecondarysecondary. . InIn chronicchronic papilloedema,papilloedema, in in additionaddition totoswollenswollen axonsaxons therethere isis extracellular extracellular accumulationaccumulation of of fluidfluid (oedema)(oedema) andand ischemiaischemia. .


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PapilloedemaPapilloedema is is nearlynearly alwaysalways bilateralbilateral. .PatientsPatients usuallyusually givesgives historyhistory of of recurrentrecurrentattacksattacks of of transienttransient blurredblurred visionvision.. VisualVisualacuityacuity inin majoritymajority of of thethe patientspatients remainsremains

normalnormal for for aa longlong durationduration. . ItIt isis affectedaffected onlyonlyinin thethe endend stagesstages whenwhen atrophicatrophic changeschangessetset inin.. SymptomsSymptoms of of associatedassociated raisedraisedintracranialintracranial pressurepressure maymay bebe presentpresent: :headache,headache, nausea,nausea, vomitingvomiting.. FieldFieldchangeschanges: : enlargementenlargement of of blindblind spotspot occursoccursinin casescases withwith fullyfully developeddeveloped papilloedemapapilloedema. .ConcentricConcentric contractioncontraction of of peripheralperipheral fieldsfieldsbecomesbecomes apparentapparent asas atrophyatrophy setssets inin..


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PapilloedemaPapilloedema shouldshould bebe differentiated differentiated fromfrompseudopapilloedemapseudopapilloedema (due(due totohypermetropia)hypermetropia) andand papillitispapillitis..

PapilloedemaPapilloedema indicatesindicates raisedraised intracranialintracranialpressurepressure andand aa neurologicneurologic pathologypathology. . TheThepatientpatient requiresrequires immediateimmediate admissionadmission toto aahospitalhospital. .


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PapilloedemaPapilloedema usuallyusually developsdevelops quickly,quickly, appearingappearingwithinwithin 11--55 daysdays of of raisedraised intracranialintracranial pressurepressure. .RecoveryRecovery fromfrom fullyfully developeddeveloped papilloedemapapilloedema is is

rather rather slowslow.. ItIt takestakes aboutabout 66--88 weeksweeks toto subsidesubsideafter after thethe intracranialintracranial pressurepressure is is normalizednormalized. .OpticOptic nervenerve atrophyatrophy isis thethe resultresult of of chronicchronicpapilloedemapapilloedema. . ItIt isis aa secondarysecondary atrophy,atrophy, whichwhich isischaracterizedcharacterized byby greygrey color color andand illill--defineddefined of of thethediscdisc duedue toto atrophyatrophy of of thethe neuronsneurons andandassociatedassociated gliosisgliosis. . VisualVisual acuityacuity isis significantlysignificantlydecreaseddecreased. .


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Optic atrophy.Optic atrophy.ItIt refersrefers totodegenerationdegeneration of of thetheopticoptic nervenerve whichwhichoccursoccurs asas anan endendresultresult of of anyanypathologicalpathological processprocessthatthat damagedamage axonsaxons ininthethe anterior anterior visualvisualsystemsystem fromfrom retinalretinalganglionganglion cellscells toto thethelaterallateral geniculategeniculatebodybody. .


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Optic atrophy.Optic atrophy.ThreeThree major major etiologicaletiological typestypes arearerecognizedrecognized: :primaryprimary opticoptic atrophyatrophy (refers(refers toto thethe simplesimpledegenerationdegeneration of of thethe nervenerve fibers),fibers),secondarysecondary opticoptic atrophyatrophy (occurs(occurs followingfollowing

anyany pathologicalpathological processprocess whichwhich producesproduces

opticoptic neuritisneuritis or or papilloedema)papilloedema) andandhereditaryhereditary opticoptic atrophyatrophy (Leber's)(Leber's). .


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Optic atrophy.Optic atrophy.

CommonCommon causescauses of of primaryprimary opticoptic atrophyatrophyareare:: multiplemultiple sclerosis,sclerosis, intracranialintracranial tumourstumourspressingpressing directlydirectly onon thethe anterior anterior visualvisualpathway,pathway, traumatictraumatic severanceseverance. .ConsecutiveConsecutive opticoptic atrophyatrophy isis thethe resultresult of of diffusediffuse chorioretinitis,chorioretinitis, retinalretinal pigmentarypigmentary

dystrophies,dystrophies, occlusionocclusion of of centralcentral retinalretinalarteryartery. . GlaucomaGlaucoma andand vascular vascular disordersdisordersmaymay alsoalso causecause opticoptic nervenerve atrophyatrophy. .


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C linic a l fe a tures of o p tic a tro ph y C linic a l fe a tures of o p tic a tro ph y ..

LossLoss of of visionvision maymay bebe of of suddensudden or or gradualgradual onsetonset (depending(depending uponupon thethe causecauseof of opticoptic atrophy)atrophy) andand partialpartial or or totaltotal(depending(depending uponupon degreedegree of of atrophy)atrophy). .VisualVisual fieldfield changeschanges willwill varyvary withwith thethedistributiondistribution of of thethe fibersfibers thatthat havehave beenbeen

damageddamaged. . TheyThey areare:: centralcentral scotomas,scotomas,differentdifferent contractionscontractions of of peripheralperipheral fields,fields,hemianopichemianopic defectsdefects. .


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O ph t ha lmosco p ic fe a turesO ph t ha lmosco p ic fe a tures ..

InIn casecase of of primaryprimary opticoptic

atrophyatrophy opticoptic discdisc isis palepale. .ItsIts edgesedges (margins)(margins) arearesharplysharply outlinedoutlined. . RetinalRetinalvesselsvessels areare significantlysignificantlyconstrictedconstricted. . SecondarySecondaryopticoptic nervenerve atrophyatrophy isischaracterizedcharacterized byby changeschangesinin color color of of thethe opticoptic discdisc.. ItItlookslooks dirtydirty whitewhite.. ItsIts edgesedgesareare notnot soso sharplysharply defineddefinedasas inin primaryprimary opticoptic atrophyatrophy. .


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T reatment .T reatment .

TheThe mainmain groupsgroups of of drugsdrugs areare:: vitamins,vitamins,vasodilators,vasodilators, drugsdrugs improvingimproving brainbrainmetabolismmetabolism. . PhysiotherapyPhysiotherapy playsplays ananimportantimportant rolerole inin treatmenttreatment of of opticoptic nervenerveatrophyatrophy: : electromagneticelectromagnetic stimulation,stimulation,infraredinfrared laser laser stimulationstimulation of of thethe opticoptic

nerve,nerve, magneticmagnetic therapytherapy or or electrophoresiselectrophoresiswithwith nicoticnicotic acidacid appliedapplied onon thethe eyeeye andandendonasalendonasal electrophoresiselectrophoresis withwith PP..iodineiodine. .

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Diseases of the Optic Nerve 09