Alterna(veTreatmentModalityintheManagementofPost-SurgicalEsotropiawithAnomalousCorrespondence

AlexandriaTilley,O.D.,TharanieAmarawardana,O.D.,KimberlyHamianO.D.,M.H.EstherHan,O.D.,F.C.O.V.D,F.A.A.O.

IntroducBonTheves(bulo-ocularreflex(VOR)occurswhenthesemi-circularcanalsdetectchangesinangularaccelera(onofthehead.Uponcessa(onofaconstant-velocitymovement,post-rotarynystagmusoccursoppositetheini(alheadrota(on.Thedirec(onofthepost-rotarynystagmuscanpromoteabduc(oninapa(entwithesotropia.Techniquesinvolvingthesesubcor(calreflexesarethebasisforthistreatmentmodality.

VesBbulo-OcularReflex•   Keepsimagesstableonthere(naduringbriefheadmovements•   Servestopreventre(nalimageslip,whichcanleadtooscillopsiaandvisualblur•   Theeyesrotateatthesamevelocity,butintheoppositedirec(on,asheadrota(on•   Example:ifoneisfixa(ngatargetstraightaheadandrotatestheirheadtotheleN,theeyes

shouldmovetotheright•   Latencyof16ms•   Madeupofaslowcomponentandafastcomponent

•   Theslowcomponent,whichisthesubcor(calpor(on,ispresentatbirth•   Thefastsaccadicreturn,whichiscor(callydriven,mayormaynotbepresentatbirth

VesBbularAnatomyPeripheralves(bularsystem(Fig.1)•   Threesemi-circularcanals•   Otoliths:utricle,saccule

Centralves(bularprojec(ons•   Ves(bularnuclei•   Ascendingtracts•   Descendingtracts

Semi-circularcanals•   Anterior(Superior)•   Posterior(Inferior)•   Horizontal(Lateral)

•   Eachsemi-circularcanalisoriented90degreesawayfromeachother•   Anteriorandposteriorcanals:oriented45degreesoneithersideoftheparasagi\alplane•   Horizontalcanal:oriented30degreesabovetheaxialplane•   Thesemi-circularcanalsactlikefunc(onalpairs

•   Ifyouexciteasemi-circularcanalononesideofthehead,youinhibittheotherontheoppositesideoftheheadthatliesroughlywithinthesameplane

Physiology•   Eachsemi-circularcanalcontainsendolymph,aviscousfluid.•   Ononepor(onofeachsemi-circularcanal,thereisadila(on,knownasanampulla,inwhicha

gela(nousmass,knownasacupula,islocated(Figure2).•   Withinthecupulaareves(bularhaircells,innervatedbybipolarsensoryneuronsofthe

ves(bularnerve.•   Withrota(onalaccelera(onofthehead,endolymph,duetoiner(a,doesnotmoveini(ally

withtheheadrota(on•   Thereisanetdisplacementoftheendolymphthatpushesonthecupula,andbendsthe

embeddedhaircells.Thiscausesreleaseofanac(onpoten(alandac(va(onoftheves(bularnerve.

References1.BaxstromC,CloptonJ.COPECourse:Ves(bularprocessing–Akeycomponentoffunc(onandbalance,January2017.2.CohenHS.Neuroscienceforrehabilita(on.Philadelphia:Lippinco\Williams&Wilkins,1999.3.LeighRJ,ZeeDS.Theneurologyofeyemovements:4thedi(on.NewYork,NY:OxfordUniv.Press,2015.4.WongAM.Eyemovementdisorders.Oxford:OxfordUniv.Press,2007.Fig1:h\ps://www.nidcd.nih.gov/health/balance/balance_disorders.aspFig2:publicdomainimage:originalsourcefromNASA’sar(cle“TheEffectsofSpaceFlightontheHumanVes(bularSystem”h\ps://commons.wikimedia.org/wiki/File:Inner_ear%27s_cupula_transmipng_indica(on_of_accelera(on.jpgFig3:“Push-pullprincipleintheves(bularsystem,forahorizontalhead-movmenettotheright:therighthorizontalsemicircularcanalgetsexcited,whiletheleNhorizontalcanalgetsinhibited”byThomasHaslwanter.GFDLPermission.h\ps://commons.wikimedia.org/wiki/File:Ves(bular_PushPull.svgTable1:Adaptedfrom:LeighRJ,ZeeDS.Theneurologyofeyemovements:4thedi(on-Table3-2.NewYork,NY:OxfordUniv.Press,2015.

CasePresentaBonA9yearoldmalepresentedtotheUniversityEyeCenterwithconcernsofdecreasedvisioninhisrighteyeandaconstantrightesotropia.Hismotherreportsthatsheini(allyno(cedtheeyeturnpriorto6monthsofage,andhehadstrabismussurgeryonhisrighteyewhenhewasfiveyearsold.Uponini(alevalua(on,hismotherreportedshedidnotwanttoundergoanotherstrabismussurgeryandwasinterestedinonlypursuingvisiontherapyPost-RotaryNystagmus•   Ajerknystagmusthatoccurssecondarytocessa(onofaconstant-velocityrota(on.•   Occurssecondarytothecon(nuedmovementoftheendolymphsecondarytoiner(alforces•   Theslowphaseoccursinthedirec(onofini(alheadrota(on,whilethefastphaseoccursinthe

oppositedirec(on.•   Forexample:ifonerotatestotheleNataconstantvelocityandthenquicklystopsmovement,a

jerknystagmuswouldbeobservedwiththeslowphasetotheleNandafastphasetotheright.

Table3:RelaBonshipBetweenSemi-CircularCanalsandExtra-OcularMuscles

DiscussionofTechniquesMonocularfixa2onwithheadrota2ons:Inordertopromoteabduc(onoftherighteye,thepa(entworeapatchoverhisleNeye.Hethenfixatedonatargetin-frontofhim.He(ltedhischindownby30degreesandrotatedhisheadfromsidetosidelaterallywhilemaintainingfixa(onstraightahead.WhenhisheadwastowardstheleNside,hisrighteye,bywayoftheves(bulo-ocularreflex,wasinaposi(onofabduc(on.Thereby,thevisual-ves(bularinterac(onwasusedinordertoincreaserangeofmo(onoftherightesotropiceye.

Spinningwithpost-rotarynystagmus:Thepa(entclosedhiseyesand(ltedhisheaddownwardsby30degrees.Hewasthenspuninachairupwardsoften(mestotheright.ANer10chairspins,hehadtoquicklystop,openhiseyes,andperformhartchartsaccades.Thistechniquewasimplementedbecauseuponstop-rota(onbotheyescon(nuedtomovewithajerknystagmus,withtheslowphasetowardstheright.Theslowphaseservedtomovebotheyestotherightinayokedfashion,promo(ngabduc(onofhisrighteyeinasubcor(calmanner,whilehavinghimperformhartchartsaccadesintroducedcor(calprocessingtothetechnique.

ConclusionS(mula(ngrota(onalinputusingpost-rotaryresponsesinvolvingvisual-ves(bularinterac(onswereu(lizedwiththispa(entsincetradi(onalbinoculartechniqueswerecontraindicatedandstrabismussurgerywasnotanop(on.Theu(liza(onoftheves(bularocularreflexandpost-rotaryresponsescanbeconsideredasanalterna(vetotradi(onalstrabismustherapy.

Ini(alevalua(on

•   DVAcc:20/200OD,20/20OS•   Refrac(veerror:+3.50sphOD,+2.25sphOS•   DCT:35ΔV-pa\ernconstantrightesotropia•   NCT:50ΔV-pa\ernconstantrightesotropia•   Extra-ocularmo(li(es:abduc(ondeficitOD,OS,DVD

nearhisneutralpoint•   Worth4Dot:esodiplopia

Re-evalua(on:session8

•   DVAcc:20/200OD,20/20OS•   Amblyoscope:Horrorfusionalisresponses•   DCT:35ΔV-pa\ernconstantrightesotropia•   NCT:50ΔV-pa\ernconstantrightesotropia

Re-evalua(onatconclusionof21sessionsofin-officevisiontherapy

•   DVAcc:20/100OD,20/20OS•   Refrac(veerror:+3.50sphOD,+2.25sphOS•   DCT:25ΔV-pa\ernconstantrightesotropia•   NCT:25ΔV-pa\ernconstantrightesotropia

Threemonthre-evalua(on

•   DVAcc:20/100OD,20/20OS•   DCT:25ΔVpa\ernconstantrightesotropia•   NCT:25ΔVpa\ernconstantrightesotropia•   AmblyoscopeanomalouscorrespondenceThepa(entwasinstructedtodiscon(nueves(bular-basedexercisestoseeifsizeofthedevia(onpersisted.

Canal Excita(on

Righthorizontalcanal RightmedialrectusLeNlateralrectus

LeNhorizontalcanal LeNmedialrectusRightlateralrectus

LeNanteriorcanal LeNsuperiorrectusRightinferioroblique

LeNposteriorcanal LeNinferiorobliqueRightsuperiorrectus

Rightanteriorcanal RightsuperiorrectusLeNinferioroblique

Rightposteriorcanal RightsuperiorobliqueLeNinferiorrectus

Techniquesusedinvisiontherapy:sessions1-7

Tradi(onalvisiontherapytechniqueswerea\empted:•   Brockstring•   Lusterapprecia(on•   Quoitvectograms•   GTVT•   Polamirror•   Accommoda(verock•   VTS3vergence•   Steppingstonestofusion•   PatchOS2hours/day

Techniquesusedinvisiontherapy:sessions9-21

Ves(bular-basedtechniqueswereused:•   Post-rotarynystagmuswithchairspinstopromote

abduc(onoftherighteye•   Monocularfixa(onswhilerota(ngtheheadlaterally•   Turnandclap•   Seevideofordemonstra(onoftechniques

PathwayoftheHorizontalVOR

Fig4.Athreetofourneuronarcexiststoconnectthehorizontalcanalstotheextra-ocularmuscles,tocauseyokedhorizontaleyemovements.

LeNHorizontalSemi-Circular

Canal

VN

AN

ON

MedialRectus LateralRectus

FigureKey:VN:Ves(bularNucleusAN:AbducensNucleusON:OculomotorNucleus

Figure1

Figure2 Figure3

Table1:ExaminaBonFindings

Table2:TherapyProtocol