LowVisionLigh+ng:ItsImportantButHowImportant?
GregoryL.Goodrich,Ph.D.VisionRehabilita9onResearchConsultant
AERBVIConference2015
Norfolk,VA
Disclaimer&Acknowledgement
• IwillspeakabouttheLuxIQfromJasperRidge.IamaresearchconsultantforJasperRidge.
• Myresearchwasapprovedbyandconductedinaccordancewithregula9onsofVAPaloAltoResearchServiceandtheVA/StanfordIns9tu9onalReviewBoard.
• Apprecia9ontoPeterBorden,Ph.D.forcontentusedinthispresenta9on.
Lightisreallyimportant
Light
Thereisan“op9mum”
Light
Whatis“op9mum”ligh9ng?
• Op9mumligh9ngisimportantinmaximizingvisualfunc9on– Formany,butnotall,lowvisionindividuals“more”lightisbeZer
• mayadd~2linesofvisualacuity
– Mayimprovethebenefitofop9calprescrip9on
• Op9mumligh9ngvariesfrompersontoperson– Notsimply“more”light– Brightnessnotonlyfactor;color,colortemperature,glare,etc.
• Aswithrefrac9ons,ligh9ngcanbemeasuredandquan9fied– Needcalibrated,fast,easilyusedmeasurementtool
www.freshnessmag.com
The“Curse”ofTerminology
Ididn’treallyunderstandligh9ngun9lIbegantounderstandtheterminology.Turnsoutitisn’tallthatdifficultonceyouhavesomeclarifica9on.
Lux??????
Candelas
Volts
??????
WhoneedsbeZerligh9ng?
• Normallysighted– Readingindimlight– Threadingneedle– Workingin9ghtspaces– Etc.
• Peoplewithvisualimpairments– Mostwithcentralfieldloss– Mostwithperipheralfieldloss– Somewithtrauma9cbraininjury
• BeZerlightinvolvesbrightness,color,glare,distribu9on
www.e-educa9on.psu.edu
Wheredoweneedop9mizedligh9ng?
health.howstuffworks.com
www.consumerreports.org
• ReadingpillboZles• Readingforwork,school,&enjoyment• Cooking&hobbies• Finances-wri9ngchecks&readingbills• Etc.
www.pinterest.com
www.moneyandstuff.info
TaskvsAmbientLigh9ng
Taskligh9ngHigherintensityLocalligh9ngOp9mizedforacuity,task,dura9on,comfort
Ambientligh9ngLowerintensityBroadarealigh9ngOp9mizedforsafety,mood
Myfocusisontaskligh9ng
pt.slideshare.net
Illuminancevs.Luminance
• Illuminance:lighthi9ngthepagelux(lumens/m2)orfoot-candles;1footcandle=10lux– Usuallydiminisheswithdistanceandanglefromsource– Independentofsurfaceproper9es(color,finish,texture)
• Luminance:lightcomingfromthepage(candelaspersquaremeter,cd/m2)– Dependsonsurfaceproper9essuchastexture,reflectance.
www.klightlab.com
www.new-learn.info
Luminanceandilluminanceinvisiontes9ng
Luminance:Built-inlight Illuminance–Reflectedlight
Rela9ngluminanceandilluminance
• Asasimpleruleofthumb,• Forareflec9vemaZesurface,
1candela/m2≈3lux(3lumens/m2)• Forexample,aback-liteyechartemits200cd/m2.
ThisisequivalenttotheilluminanceonawhitemaZeeyechartina600luxexamroom.
=
Commonilluminancevalues
Starlight .0001luxFullmoon .27–1luxGeneralresiden9alligh9ng 50–100luxVerydarkovercastday 100luxResiden9aldiningroom 100–200luxResiden9alreading 200–500luxClassroom,brightlitexamroom500–1,000luxOvercastday 1,000luxFulldaylight 10,000–100,000lux
www.ltlmagazine.com
Source:ReaMS.Ligh@ngHandbook:[email protected]:Illumina9ngEngineeringSocietyofNorthAmerica;1993;Wikipedia
Measurementofligh9ng
• Lightmetersmeasureilluminanceineither– Lux,or– Footcandles
• Rela9velyinexpensive– ~$30.00andup
Illuminanceandangle
• Illuminancedependsonanglebetweenlightsourceandreflec9ngsurface.Thelowertheanglethelowertheilluminance.
Textatangleincreasesarea:lowerilluminance
SourceTextfacingsource:higherilluminance
Keyproper9es:Color
• Colorarisesfromthemixofwavelengthsinthesourcelight• Monochroma9clighthasonewavelength:
– Green=~527nm– Red=~630nm
• Mixingcolorscreateshues(Moreonthislater)
Keyproper9es:Contrast
• Contrast=differencebetweenbackgroundandtext• 100%contrastispureblackonpurewhite• Eyechartsouenhave80%contrastwhilemanyreading
materialshavelowcontrast• Contrastisapropertyofthemedium-ligh9ngorfiltersdo
notchangeit.
The Daily Mar+ansinvadeearth
Contrast
• Commondefini9onis:
– Perfectlywhitepagewithblacktesthascontrastof1or100%– Anewspapermighthavedarkgreyprint(75%reflec9on)onlightgrey
paper(15%)yieldingacontrastof67%
• Ligh9ngorfiltersdonotchangecontrast!
Contrast = RMAX − RMINRMAX + RMIN
Keyproper9es:Glare
• Unwantedlightfromwindow,lamp,reflec9ons,orthepageitself.
• Glarecanbedifficulttocontrolwhenprovidingbrightlight.
Glare:Reducesperceivedcontrast
• Ligh9ngdoesnotchangeactualcontrast,butreducesre9nal(perceived)contrast
NoglareContrast=(100–10)/(100+10)=82%
GlareContrast=(120–30)/(120+30)=60%
102030
100120
Luminance
Text Page Text Page
Glare:Example
Clockonnightstandwithout(clockfacevisible)
Andwithbrightglaresource(clockfacenotvisible)
Awaytoreduceglare
Brightness:Steven’sPowerLaw
Theeye’ssensa9onofhigherintensitydecreasesastheintensityincreases.Onlylargechangesinbrightnessareeffec9ve.Thismayincreaseglareunlessligh9ngiscarefullycontrolled.Example:3-waybulbwith50,100and150waZsoutput.Thedifference,50waZs,isthesamebetweeneachseyng.0to50waZsismoreno9ceablethan100to150waZs.Schwartz,VisualPercep9on,4thedi9on
Intensity
Sensa9on
Warmandcoolwhite
“Warm”hasmorered “Cool”hasmoreblue
Lightshavea(non-intui9ve)colortemperature(oKelvin)
• Thehigherthetemperaturethecoolerthelightcolor)
Warmer
Cooler
AMDandmorelight
• Mostnormallysightedfolkreachpeakacuityat500lux(normaltaskligh9ng).**
• AMDpa9entsmayneed>4Xor2000luxtoachievepeakacuity.
• Mostpreferbrighterlight
www.pinterest.com
**Moreaboutthislater–ligh9ngtomaximizeacuityandpreferredligh9ngforreadingaredifferent.
WBRCStudy
• Designedtocomparevisualacuity(highandlowcontrast)fornormalsandlowvisionpa9ents
• ComparedacuitymeasuredintheclinicwiththatobtainedusingtheLuxIQ– Subjectsset:
• Brightness• Colortemperature
• Counterbalancedorderofpresenta9on
WBRCStudypar9cipants
Controls(N=10) SubjectsN=30)
MeanAge 55.5yrs.(40-68) 70.7yrs.(51-90)*
WorkingDistance 44.7in.(32-56cm) 26.3in.(12-45cm)**
64.6 65.0 64.9 65.0
63.3 64.6 64.7 65.0
42.547.7 47.9* 50.5*
25.9
30.1* 33.1*35.4*
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
Clinic LuxIQ-White LuxIQ-Temperature
LuxIQ-Green
NofC
haractersR
ead
ControlsHigh
ControlsLow
SubjectsHigh
SubjectsLow
64.6 65.0 64.9 65.0
63.3 64.6 64.7 65.0
42.547.7 47.9* 50.5*
25.9
30.1* 33.1*35.4*
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
Clinic LuxIQ-White LuxIQ-Temperature
LuxIQ-Green
NofC
haractersR
ead
ControlsHigh
ControlsLow
SubjectsHigh
SubjectsLow
• Controlssignificantlyyoungerthansubjects• Controlsusedsignificantlygreaterworkingdistances• Subjectshadvarietyofpathologies
• AMD=8• Glaucoma=8• OtherTBI(hemianopia),NAION,diabe9cre9nopathy,trauma/TBI,
inters99alkera99s,CRAO,andmacularedema• Controlspreferredgreaterbrightnessthansubjects• Subjectsusedbestnearcorrec9onforallcondi9ons
Ligh9ngmeasurementtools:LuxIQ
• Leuslidercontrolsbrightness– 0to5,000lux
• Rightslidercontrolscolortemperature– 2,700to6,300oK
• Slidersmoveleutorighttoincreasebrightness/colortemperature
• Readingsfromscalesabovesliders
• Colenbranderhigh/lowcontrastnearacuitychart
• RecordednumberofleZersread
Controlledstudyofbrightnessandcolortemperature
• Controlspreferredsignificantlybrighterlight– Controls:500–5000lux– Subjects:700–5000lux
• Nosignificantdifferencebetweennormalandcontrolpopula9onsoncolortemp.– Controls:2700–5500oK– Subjects:2700–6500oK 500lux=valuewherenormallysightedreach
asymptoteforvisualacuity
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Brightness ColorTemp.
Controls
Subjects
2825
1954
42604400
NumberofleZersread
0
10
20
30
40
50
60
70
ControlsHigh ControlsLow SubjectsHigh SubjectsLow
Clinic
LuxIQwhite
LuxIQTemp
*• MaximumleZers=65• Nosignificantchangefor
controls• Comparedtoclinic
illumina9onsubjectsreadsignificantlygreaternumberofcharactersonbothhighandlowcontrastcharts
• Gainvariedbysubjectfromnoaddi9onalleZerstoover2lines
*
**
StudyConclusions
• Bothcontrolsandsubjectspreferredbrightlight(controlssignificantlymore)
• Controlsandsubjectsverysimilarinpreferredcolortemperature• Brightnessandcolortemperaturesignificantlyimprovednumber
ofleZersreadonhighcontrastforsubjectsbutnotcontrols• Brightnessandcolortemperatureeachsignificantlyimproved
numberofleZersreadonlowcontrastforsubjectsbutnotcontrols
• Op9mizedligh9ngenhancedeffec9venessoflowvisionprescrip9on
• Lowvisionindividualsusingop9mizedligh9ngreadsmallerprint;op+mizedligh+ng=magnifica+on
Caveats
• Notallsubjectspreferredorbenefitedfrombrighterlight– EvenamongAMDpa9entswhoarethoughttoneedmorelight
• Preferenceforligh9ngisindividualforbothcontrolsandlowvisionsubjects
• Individualmeasurementandprescrip9onofligh9ngshouldimprovelowvisionindividual’sperformanceonneartasks
Relatedstudies
• RotruckandFletcher(ARVO2015)– POAGpa9entsprefersignificantlylesslightthanAMDpa9ents
• POAG2,345lux(±922);AMD4,289lux(±713)
– Op9mumligh9ngsignificantlyimprovesacuityHicontrast 1.8M 1.2MLowcontrast 6.6M 5.2M
Room(500lux) Op9mum
Prescribingligh9ng
• Currentstandardistrialanderrorlackingsystema9c,calibratedbasis
• LuxIQoffersacalibratedop9on– Ithasbeenshowntoimproveacuityandmayimprovevisual
comfortforlowvisionreaders.
Swappingbulbs …orlamps
Nextsteps
• I’macardcarryingresearchersoofcourseI’mgoingtotellyoumoreresearchisneeded– Doesop9mumligh9ngimprovereadingdura9on?– Doesimprovementtranslatetoothertasks?– Studiesdonearewithadults,doesthebenefittranslatetochildren?
• StudywithchildrenwithCVIstar9ngupatCaliforniaSchoolfortheBlind(Marasch,Lueck,&Goodrich)
– LuxIQ2mayprovidecalibratedtoolforprescribing9nts/filters?
ResearchFindingsReferences(availableatwww.jasperridge.net)
• AAO2013– Quan9fyingPa9entLigh9ngNeedstoImproveLowVisionClinical
Prac9ceandPa9entPerformance-GregoryL.Goodrich,ShanidaIngalla,MeganDolkas
• Envision2014– IsLowVisionLigh9ngComingofAge-GregoryL.Goodrich,Donald
Fletcher,KarenKendrick,FaydimRassamdana– Measuringandprescribingpreferredlightintensityandcolor-Peter
Borden,MicheleKlein• ARVO2015
– Pa9entswithAMDandPOAGmayrequiredifferentligh9ngtomaximizevisualacuity-JillRotruck,DonFletcher;LauraWalker
– Func9onalImpactofTaskLigh9ngonReadingwithLowVision-TonyA.Succar,LauraWalker,KarenKendrick,AndraMies,DonaldC.Fletcher
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