2016 i. binocular vision & retinal correspondence; ii amblyopia
TRANSCRIPT
Alvina Pauline D. Santiago, MD Pediatric Ophthalmology & Adult Strabismus Basic Course Lectures in Ophthalmology Sentro Oftalmologico Jose Rizal Philippine General Hospital September 2016
¡ Correspondence&disparity§ sensorybinocularcooperationbasedoncorrespondence&disparity
§ singlevisualimpression,nodepth§ binocularrivalry:diplopia§ horizontaldisparity:depthwithinPanum’sfusionalspace
¡ Horopter§ locusofallobjectptsimagedoncorrespondingretinalelementsatagivenfixationdistance
¡ Panum’sfusionalspaceorareaofSBV§ regioninfrontofandatthebackofthehoropterthatstillallowsSBV
§ allowsdepthperception
¡ Horopter§ Ellipticallinethatstimulate
correspondingpointsontheretina
¡ Panum’sfusionalspace§ Areainfrontandbehind
horopterwhereobjectsstimulatenoncorrespondingpointsandyetarestillfusibleasoneretinalimage
Figure from Wright’s Pediatirc Ophthalmology
¡ Uncrosseddiplopia
¡ Crosseddiplopia
Figure from Wright’s Pediatirc Ophthalmology
¡ Neurophysiologictheory§ visualstimulifromretinatovisualcortexmodifiedandcoded
§ only25%binocularlydrivencellsarestimulatedequally;75%gradedinfluencefromR&Leye
§ Macaquemonkey:Ar18;Rhesus:Ar17-18§ Lostbinocularneuronsdonotrecover
¡ Reducedpanoramaofvision¡ Uprightposition¡ Frontaleyeposition¡ Visuomotortasksimproved¡ Depthperception¡ Orientationofbodytoenvironment
From Adler’s Physiology of the Eye
From Cybersight.org: Compilation of behavioral data from different studies showing the development of binocular grating acuity in humans over the first 5 postnatal years. (From Teller DY, Movshon JA: Visual development. Vision Res 26:1483, 1986.)
¡ FinevisualdiscriminationcharacteristicofhighVArequiresharplyfocusedsmallobjectsasappropriatestimuli
http://www.macuhealth.com
From Rosenbaum & Santiago Clinical Strabismus Management
¡ 2mirrorsatelbowthatreflectimagesfrompictureslides
¡ armsmaybemovedtoaligntargetsoneachfovea
From Rosenbaum & Santiago Clinical Strabismus Management
¡ Subjectiveangle§ amountindegreestheexaminermustmoveamblyoscopearmsforpatienttosee2picturesassuperimposed
§ duringbinocularviewingconditions¡ Objectiveangle
¡ Subjectiveangle¡ Objectiveangle
§ deviationmeasuredbyalternateprismcovertest§ duringmonocularviewingconditions
¡ Angleofanomaly§ displacementofthetruefoveafrompseudofovea§ zeroifNRC;subjective=objectiveangle§ (+)ifalternatecovertest(objectiveangle)isnotequaltosubjectiveangle
¡ Firstdegree(simultaneousperception)§ Dissimilartargetspresented§ Perceivedatthesametimeinthesamevisualdirection
¡ Seconddegree¡ Thirddegree
¡ Firstdegree(simultaneousperception)¡ Seconddegree(flatfusion)
§ similartargetswithdissimilarcomponents(monocularsuppressionchecks)
¡ Thirddegree
¡ Firstdegree(simultaneousperception)¡ Seconddegree(flatfusion)¡ Thirddegree(stereopsis)
§ Sametargetsas2nddegree+disparity
¡ Firstdegree§ simultaneousperception
¡ 2nddegree§ flatfusion
¡ 3rddegree§ Stereopsis
From Rosenbaum & Santiago Clinical Strabismus Management
¡ RE:circle¡ LE:blackdot
¡ Orthotropic¡ Blackdotincircle
From Wright’s Pediatric Ophthalmology
¡ Organizationofvisualspaceissuchthatthevisualdirectionofeachfoveaisthesame
¡ Angleofanomaly=0¡ PatientswithNRCalwaysusefoveaascenterofreference
¡ Toseeblackdotincircle,needtomovearmsofamblyoscopetotalof40PD
From Wright’s Pediatric Ophthalmology
¡ Ifwithdenselargeregionalsuppression,nosubjectiveangle,difficulttosuperimposeimages
¡ Ifmonofixator,usetargetsforperipheralretina
¡ subjectiveangle=0§ measuredunderbinocularconditions
§ Pseudofoveacompensatesforangleofdeviation
§ Nosubjectivemisalignment
From Wright’s Pediatric Ophthalmology
§ pseudofoveadoesnotcompensatefullyforangleofdeviation
§ Angleofanomaly=objectiveangle-subjectiveangle
From Wright’s Pediatric Ophthalmology
¡ Measuresfusionalvergengeamplitudes¡ Angleofdeviation¡ Areaofsuppression¡ Retinalcorrespondence¡ Torsion¡ Instrumentconvergence
¡ Retinalcorrespondence§ singlevision:hallmark
¡ ARCvsNRC¡ Retinaldisparity&rivalry:
§ diplopiaandvisualconfusion
¡ Diplopia¡ Visualconfusion¡ Suppression¡ Horrorfusionis¡ Anomalousretinalcorrespondence
¡ Diplopia§ Objectofinterestseenbyfoveaofoneeyeandperipheralretinaoftheothereye
¡ Visualconfusion
§ Foveaofbotheyes(orcorrespondingretinalpoints)sees2objectsofinterestinterpretedascomingfromthesamepointinspace
From Rosenbaum & Santiago Clinical Strabismus Management
¡ Suppression:alterationofvisualsensationthatresultsininhibitionorpreventionofoneeye’simagefromreachingconsciousness
¡ Physiologicsuppressionpreventsphysiologicdiplopiafromreachingconsciousness
¡ Central:§ pathologicextensionofretinalrivalry§ preventsfovealimageofdeviatingeyefrombeingperceived
¡ Peripheral:§ Preventsawarenessoftheimageonperipheralretina(2ndimage)
Esotropia Exotropia
From Rosenbaum & Santiago Clinical Strabismus Management
¡ Monocular:unidirectional§ Dominanteyealwayspredominateoverimagefromdeviatingeye
¡ Alternating:bidirectional§ Suppressionswitchesbetweenthetwoeyes
¡ Facultative§ Presentonlywheneyesaredeviated
¡ Obligatory§ Presentatalltimes,whethereyesaredeviatedoraligned
¡ Etymology:dullnessofvision§ Greek:▪ amblyos=dull▪ Stem:ops=vision
¡ Observer(MD)seesnothing,andthepatientseesverylittle
▪ vonGraefe
¡ UnilateralorbilateraldecreaseinVAcausedbypatternvisiondeprivationorabnormalbinocularinteractionforwhichnocausecanbedetectedbyphysicalexamination,andwhichinappropriatecases,reversiblebytherapeuticmeasures
▪ vonNoorden
¡ Approximately2-2.5%ofgeneralpopulationhasamblyopia
§ MilitaryRecruits 1-3.2%§ Preschoolchildren 0.5-3.5%§ Ophthalmicpatients 4-5.3%
¡ Abnormalbinocularinteraction¡ Fovealpatternvisiondeprivation¡ Combinationofboth
¡ Mostsensitivefirst2-3years
¡ Decreasesuntilage6-7years§ completevisualmaturation
§ retinocorticalpathwaysandvisualcentersresistanttoabnormalvisualinput
From Adler’s Physiology of the Eye
¡ Reversible(functional)§ Strabismicamblyopia§ Anisometropic/ametropicamblyopia§ Visualdeprivationamblyopia§ Idiopathicamblyopia§ Toxic/Nutritionalamblyopia
¡ Irreversible(organic)§ Amblyopiainnystagmus§ Otherocularpathologies
¡ HigherprevalenceinETthanXTbecauseofnasotemporalasymmetryofretinocorticalprojections
¡ ET:foveaofdeviatingeyecompeteswithstrongtemporalfield
¡ XT:foveacompeteswithweakernasalfield
¡ alwaysunilateral,§ causedbyactiveinhibitionofretinocorticalpathwayoriginatingfromfoveaofdeviatingeyeduetovisualconfusion
§ lackofadequatestimulationofthefovea¡ Durationofstrabismusratherthanageattimestrabismusdevelopscorrelatesmorecloselywithamblyopia
® Double vision: diplopia ® obj of interest seen by fovea of one eye
and peripheral retina of other eye ® Visual confusion
® fovea of each eye sees 2 different obj interpreted by brain to be in the same visual direction
From Rosenbaum & Santiago Clinical Strabismus Management
Esotropia Exotropia
From Rosenbaum & Santiago Clinical Strabismus Management
NORMAL Figure from Wright’s Pediatirc Ophthalmology
¡ EccentricFixation¡ AnomalousCorrespondence¡ Lossoffusion¡ Retinaldisparityandrivalry¡ Crowdingphenomenon¡ Smoothpursuitasymmetry
¡ Bothoccurtoeliminatevisualconfusionfromdissimilarretinalimages
¡ Suppressionoccursonlyunderbinocularconditions
¡ Amblyopiapersistsafterclosureoffixatingeye
¡ Activeinhibitionoffovea¡ Eliminatesensoryinterferencecausedbysuperimpositionofafocusedanddefocusedimage(abnormalbinocularinteraction)
¡ Aniseikoniamaybeafactor¡ Fovealpatternvisiondeprivation
¡ Disuseorunderstimulationofretina¡ Unilateralmoreseverethanbilateral¡ Bothpatternvisiondeprivationandabnormalbinocularinteractionarefactorsinmonocular
¡ Onlypatternvisiondeprivationinbinocular
Causes AbNbinoc Form interaction Deprivation
Strabismus + -Anisometropia + +VisualDeprivationUnilateral + +Bilateral - +
¡ Superimposedfunctionalcomponentcanbeimprovedwithamblyopiatherapy
¡ Wrongorientationofretinalreceptors?¡ Changesinlateralgeniculatenucleusandstriatecortex
¡ Fixationpreference§ butmanynormalpatientshavefixationpreference
¡ Crossedfixation§ doesnotalwaysimplyabsenceofamblyopia
Figure from Wright’s Pediatirc Ophthalmology
Figure from Wright’s Pediatirc Ophthalmology
Figure from Wright’s Pediatirc Ophthalmology
¡ Visualacuity§ differenceinacuityin2eyes§ butcertainsmalldifferenceexistinnormalpopulation
§ differenceof2linesformostclinicalpurposes
¡ Occlusionorpatchingeveninnystagmus¡ 1weekperyearoflifethenreevaluate
§ doesnotsignifyendoftherapy§ evaluateocclusionamblyopia
¡ Fulltimevsparttime¡ Roleoftapering
¡ 3-6weeksinolderchildbecauseofschool¡ Rationale:
§ forcetousethebadeye§ allowsneuralcircuitrytobereestablished
¡ Penalization§ Atropine(Hunter,JohnsHopkinsprotocol)§ Opticalpenalization(overplus:fogging)§ Neutraldensityfilters§ Blurringbettereyebyanymeans
¡ Stageofmaturityofvisualconnectionsatwhichabnormalvisualexperiencebegan
¡ Typeofabnormalvisualexperience§ amblyopiamorecommoninETthanXT§ mayberelatedtonasotemporalasymmetry(strongertemporalhemifield)
¡ Durationofdeprivation¡ Ageatwhichtreatmentwasstarted¡ Compliance¡ Neurologicstatus¡ Psychologicalandpsychosocialconsiderations
¡ Patientcompliance&acceptance¡ Parentalunderstandingofrationale¡ Parent-childdynamics¡ Poorfollow-up¡ Smartchildrenmemorizecharts!¡ Differingmethodsofassessment¡ Whentostoppatching?
¡ Singleoptotypeimprovesmorerapidlythanlineacuity
¡ Crowdinghasprognosticvalue¡ SingleEacuityrepresentstruepotential¡ Differentcharts,differentresults
From Adler’s Physiology of the Eye
Figure from von Noorden’s Binocular Vision
¡ Maximizeamblyopiatreatmentpriortostraighteningeyes
¡ Enhancesfusion-lock¡ Morepracticaltostartpatching,continueevenaftersurgery
¡ Rosenbaum&Santiago:ClinicalStrabismusManagement
¡ VonNoorden:BinocularVisionandOcularMotility
¡ Wright:PediatricOphthalmologyandStrabismus¡ Taylor:PediatricOphthalmology¡ Nelson:PediatricOphthalmology¡ Moses&Hart:Adler’sPhysiologyoftheEye¡ PEDIGAmblyopiaStudies