Entoptic phenomena

What happen when the eye sees itself?
Why some times we see white spots and flouters?

1. Entoptic phenomena
BY: ASMAA J. ABDALWAHID
1
The First &The Only Franchise in the Country

2. Entoptic phenomena
2
EntopticPhenomenaliterallytranslatesas“phenomena
insidetheeye”.Theyarevisualeffectsandsensations
thatoccurfromcauseswithinthehumaneyeitself.So
theeyeseesitself.
Thesephenomenamayresultfromeithernormal
anatomiccomponentsoftheeyeorpathologic
imperfections.

3. Entoptic phenomena
3
Theopticalillusionsarecausedbythevisualsystemby
causingthingsdoesn’texist,orpicturesthatwe
perceivedifferentlythantheyreallyare.
Becauseentopticimagesarecausedbyphenomena
withintheobserver'sowneye,theobservercannot
shareadirectandspecificviewofthephenomenon
withothers(thesamewithillusions).

4. 4
Entoptic
phenomena
Media
-Floaters and flashes
-Shadows
-Mosaic patterns
-Haloes
Vascular
-Purkinje tree
-Blue field
Central vision
& pigmentation
-Haidinger’s brushes
-Maxwell spot
Retinal process
& neuron action
-Blue arcs
-Retinal photopsiasand phosphene

5. Entoptic phenomena-Media
5
Theopticaldensityandtherefractiveindexofthestructuresare
importantintheformationofentopticphenomena.
Thelocationoftheinner-eyestructureandchangingtheilluminating
angle,theeyecandetectthedirectionofthemovementoftheshadow
thatthestructurecauseditaccordingtothelocationfromthepupil:
1.Opacityinastructurebehindthepupil:theshadowsarecastontheretinawill
moveintheoppositedirectiontotheilluminatingsource.
2.Opacityinastructureinfrontofthepupil:theshadowsarecastontheretinawill
movewiththedirectionoftheilluminatingsource.

6. EP -Media
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Thestructure’sdistancefromthepupilalsoplaysanimportantrole.The
furtherawaythestructureisfromthepupil,agreatershiftofthe
shadowisobserved;sopatientsaremostdisturbedbyopacitiesthatare
locatedintheposteriorvitreousbody.
EntopticphenomenaoccursbecauseoftheOpticmedia,areresulting
from:
1.Refractivecauses:occurwhenthelightpassesthroughstructureswith
differentdensity,changingitsdirection,whichisperceivedasashadow
2.Diffractivecauses:occurfromthelightbendinganddispersingonthe
fringesofimperfectionsoftheopticalsystem,whichisperceivedasa
halos

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Refractive
Cause
Posterior
segment
-Degenerativechangestothevitreous(Agingchanges)causing
floatersandmovingspots
-Vitreoushemorrhage(becauseofretinaltearsordetachment,
choroidalmelanoma,occlusionofretinalveins,diabetes
retinopathy)
Anterior
segment
-Jumpingshadowsfromtheeyelashes(sometimewithcolours
becauseofdiffraction)
-Excessivemucusandoilexcretionfrommeibomianglandscan
resultin(cornealmosaicpatterns)
-FoldsoftheDescement’smembrane(Cornealdeformations
resultingfromincorrectlywearingrigidcontactlenses)
EP -Media

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VitreouschangesandtheFloaters(muscavolitans)
-Floatersorflyingflies:aresmallspots,mostofthemaresmallprotein
calledcollagen
-Floatersusuallyhappenbecauseofnormalchangesintheeyeswith
theage(andmorelikelyinmyopiceye)
-Withtheage;thevitreousbodystartstoliquefyandthestructureof
collagenfibrilsbreaksdownandsticktogethertocastshadowsonthe
retina
-Theshadowsofthoseopacitiesappearasthefloaters(spots)
-Theyusuallydon’ttotallygoaway,andtheymoveastheeyemoves
-Blinkingdoesnotremovethefloaters
-Floaterscouldbealsoduetointernaleyeinflammationandinfection
EP -Media

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VitreouschangesandtheFloaters
-Theybecomemostnoticeablewhenlookingintoabrightand
uniformlyilluminatedlightsource(theskyorawhitepaper)
-Itdoesnotneedatreatment,butifthepatientsawaflash,asudden
increaseinthenumberoffloaters,lossofsidevisionandadropinthe
vision,heneedstoseeadoctorimmediately,becausethismeansthere
is:
-Retinaldetachment
-Vitreousdetachment
-Bleedinginvitreous
*Visualauracancomewithamigraineheadacheandlastfor30min
EP -Media

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11. Floaters
Flashes
Aura
Illusion

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Diffractive
Cause
Pathological
-Cornealhalo
Physiological
-Ciliarycorona
-Lenticularhalo
EP -Media

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•Differentstructureinsidetheeyecausediffractionwhenthe
lightbendfromtheiredges.Theresultisadeclineinthe
contrastoftheimageandtheonsetofrainbowhalos
•Thesizeoftheperceivedhalosdependsonthedistance
fromthestructure,ofwhichthelightisdiffracted,tothe
retina.Thecloseritistotheretina,thesmallerthehalowill
be
•Thesephenomenacanoccurinnormaleye(physiological),
andalsoin(pathologic)conditions
EP -Media

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•Pathologicalphenomenaincludecornealhalo
⁻Cornealhalooccursbecauseofcornealedema,causinglight
scatteringinalldirections.
⁻Whenviewingwhitelight,awhitecentralcirclecanbeperceived,
surroundedbymulticolouredrings
•Physiologicalphenomenaincludetheciliarycorona,and
lenticularhalo
EP -Media

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⁻Ciliarycoronaoccurwhenwatchingasingularilluminatedobjectin
thedark(e.g.,astreetlamp),theilluminationsourceissurrounded
byahalowithslightlycolouredneedles.
⁻Thisistheresultofthelightreflectingfromnumeroustinyparticles
(proteins)inthelensnucleus,andthetinyirregularitiesinthe
structureofotherocularparts(depositsonthecornealendothelial
cells,thecellsintheanteriorchamberandtheanteriorlenscapsule)
⁻Lenticularhalomayoccurwhenthepupilisdilatedinadimarea,a
ribbonofcolouraroundtheilluminationsourcewillappear
⁻Itiscausedbylightbouncingfromthezonularandanteriorpartsof
thelens
EP -Media

16. Corneal halo Ciliary corona
IllusionLenticular halo

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18. Entoptic phenomena-Vascular
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•Undernormalconditionsretinalvesselsarenot
visiblebecauseofneuronadaptation
•Theentopticviewoftheretinalvesselshasmany
characteristicsofanafterimage.Itremainsvisible
aftertheintermittentshortstimulushasstopped
•ThisincludePurkinjetreeandBluefield

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•ThePurkinjetree(Retinalvesselsimage)
⁻Ifweshinealightintotheeyefromanusualangle,theshadowsof
thevesselswillcastontheretina.Thisallowspatientstobrieflysee
theretinalvascularimage(Patientsbeingexaminedbya
biomicroscopeoftennoticetheretinalvascularimage)
⁻Itcanbeseenbyshiningabright,movinglightlikeapenlightonto
thesclera(thewhiteoftheeye)inadarkenedroom.
⁻Theshadowscastbytheretinalvessels,remaininfixedposition,
evenduringeyemovementsbecauseofthe(afterimage).
EP-Vascular

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•TheBluefieldphenomenon(Scheerer'sPhenomenon)
⁻Theblueskyspritesaretinybrightdotsmovingquicklyalong
squigglylinesinthevisualfield,especiallywhenlookingintobright
bluelightsuchasthesky.
⁻Thedotsthemselvesaretheresultofwhitebloodcellsmovingalong
capillariesinfrontoftheretina(thedotsthemselvesaresmalland
white,andtheyappearslightlyelongatedwithdarktailswhichare
redbloodcells).
⁻Sphericalwhitebloodcellistoowideforthecapillary,andredblood
cellsgetbackedupbehindthem(creatingtheappearanceofawhite
dotwithatail)
EP-Vascular

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•TheBluefieldphenomenon(Scheerer'sPhenomenon)
⁻Bluelightisabsorbedbytheredbloodcellswhichfillthecapillaries.
Andthewhitebloodcells,whicharemuchlessthantheredonesand
donotabsorbbluelight,butallowedtopasstotheretinamakinggaps
appearasthespots
⁻Thedotsappearinthecentralfieldofview,within10to15degrees
fromthefixationpoint.Thedotswillnotappearattheverycenterof
thevisualfield,becausetherearenobloodvesselsinthefoveal
avascularzone.
EP-Vascular

22. EP-Vascular
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•TheBluefieldphenomenon(Scheerer'sPhenomenon)
⁻Scheerer'sphenomenoncanbedistinguishedfromvisualsnow
becauseitappearsonlywhenlookingintobrightlight,whereas
visualsnowisconstantlypresentinalllightconditionsincludingthe
dark.
*Visualsnowsyndrome(VSS)isan
uncommonneurologicalconditionthat
causethepatienttoseepersistent
flickeringwhite,black,transparent,or
coloureddotsacrossthewholevisualfield.
Ithasnocureandtreatmentyet. Visual snow

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Purkinje tree Blue field

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•Thecenteroftheretinaisthemacula,andthecenterofitthere
isthefovea(maculalutea-yellowspot)whichresponsiblefor
centralvision.It'sthepointatwhichvisualacuityisatits
highest.
•Inthefovea,thereareNOrods(onlycones),andthereisno
bloodvessels(avascular).
•Centralvisionphenomenaisduetotheabsorptionofbluelight
byayellowpigmentinthemaculacalledxanthophyllwhichacts
asyellowfilter
•ItisincludeHaidinger’sbrushesandMaxwell’sspotphenomena
Entoptic Phenomena -Central Vision

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•Haidinger’sbrushesphenomenon
⁻Apaleinterlinkedblueandyellowbarorbowtieshape,visibleinthe
centreofthevisualfieldagainsttheblueskyviewedwhilefacingaway
fromthesun.Oronanybrightbackground,duetolightpolarization.
⁻Centralvisionphenomenaisduetotheabsorptionofbluepolarized
lightasaresultofdichroicxanthophyllpigment
⁻Thedirectionoflightpolarizationisperpendiculartotheyellowbar(i.e.,
verticalifthebarishorizontal).
⁻Haidinger’sbrushisformedonlyonthemaculaandcenteredonthe
fovea,sowecanuseittomeasureeccentricfixationanddetectany
macularproblemearly
EP-Central Vision

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•Maxwellspot
⁻Adarkspotcanbeseeninthecentreofthevisualfieldsurroundedbya
brightercirclewithahalowhenawhitesurfaceisviewedbyanormal
observerthroughadichroicfiltertransmittingredandbluelights.
⁻Thecentraldarkcircleistheresultofbluelightabsorptioninthe
xanthophyllpigmentofthecentralfovea.
⁻Thephenomenoncanbeusedtotesteccentricfixation.
*Eccentricfixationmeanstheeyeusesaportionoftheretina
otherthanthefoveaforfixation.
EP-Central Vision

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Maxwellspot Haidinger’s brushes

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•Thestimulationoftheretinalreceptorswithanenergyother
thanthelightenergy,mayleadtothosephenomena,which
includeBluearcandPhosphene
•Bluearcs
⁻Itisviewingtwopalebluearcsaboveandbelowthefixationpoint
forashortperiodoftimecomingfromelectronicdevicesorartificial
lightingindarkroomasaresultofsecondaryelectricalstimulationof
theretina
⁻Thepositionandorientationofthearcsarecorrespondtoarcuate
nervefiberbundlesextendingtotheopticdisk
Entoptic Phenomena –Retinal & Neuron Action

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•PhotopsiasandPhosphene
⁻Photopsiasareperceptionsoflightwithoutanactuallightbecauseofthe
pressureontheretinawhichresultsinactivationofretinalganglioncells
⁻Photopsiasoccurasresultofdirectretinalstimulation
⁻Thepersonseescolorfulshapesandlight,geometricpatterns,sparksand
zig-zaglines,floatingshapes,movingdots,…etc.
⁻Photopsiascanoccurbeacauseofnumerouspathologicalocularor
systemicconditions
⁻Phosphenesareasubgroupofphotopsias
⁻Phosphenesiscanbeinducedbymechanical,electrical,ormagnetic
stimulationoftheretina,visualcortex,oranypartrelatedtotheeye,
theyaremoreintenseandofshorterduration
EP –Retinal & Neuron Action

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Phosphenes
Bluearc

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•PhospheneCauses
1.Mechanicalstimulation:Themostcommonphosphenesarepressure
phosphenes,causedbyrubbingorapplyingpressureontheclosedeyes.
Pressuremechanicallystimulatesthecellsoftheretina
Anothercommonphospheneis"seeingstars"fromasneeze,laughter,a
heavyanddeepcough,blowingofthenose,ablowontheheadorlowblood
pressure
Lesscommonly,phosphenescanalsobecausedbysomediseasesofthe
retinaandnerves,suchasmultiplesclerosis
EP –Retinal & Neuron Action

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•PhospheneCauses
2.Electricalstimulation:Phosphenescanbecreatedbyelectricalstimulation
ofthebrain.
3.Others:
Transcranialmagneticstimulationandmagneticfield.
Radiationofspaceorradiotherapycausephosphenes(pateintsreported
seeingblueflashesoflight)
Phosphenescanbecausedbysomemedications,suchasIvabradine(usedto
treatheartfailure)
EP –Retinal & Neuron Action

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•PhotopsiasCauses
⁻Causes:
1.Peripheralvitreousdetachment:ifitoccurstoorapidly,itcancause
photopsiawhichmanifestsinflashesandfloatersinthevision,separation
ofposteriorvitreousfromtheopticdiskresultsinappearanceofcentrallarge
annularopacity(Weissring)
2.Maculardegeneration:thesecondmostcommoncauseofphotopsia
3.Retinaldetachment
4.Ocularmigrainecausevisualauras
5.Opticneuritis;aninflammationthatdamagestheopticnerve
6.Neurologicalcausessuchaspoorbloodflowtothebackofthebrain
EP –Retinal & Neuron Action

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•PhotopsiasCauses
7.Thepresenceofthepermanentvioletflashingindicatesaretinalischaemia
(noenoughblood)
8.Proliferativediabeticretinopathy
9.CharlesBonnetSyndrome(CBS):Aphenomenonaffectingpeoplewho
havepartiallyorcompletelylosttheirsight,inwhichtheystill“see”things
thataren’tthere
10.Retinitispigmentosa
11.Bloodpressureproblems
EP –Retinal & Neuron Action