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Permanent Link: http://ufdc.ufl.edu/IR00002520/00001
 Material Information
Title: Choosing Sunglasses
Physical Description: Fact Sheet
Creator: Harrison, Mary N.
Publisher: University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication: Gainesville, Fla.
Publication Date: 1991
 Notes
Acquisition: Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status: Published
General Note: "Publication date: October 1991."
General Note: "HE 5200"
 Record Information
Source Institution: University of Florida Institutional Repository
Holding Location: University of Florida
Rights Management: All rights reserved by the submitter.
System ID: IR00002520:00001


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FactSheetHE5200 TheInstituteofFoodandAgriculturalSciencesisanequalopportunity/affirmativeactionemployerauthorizedtoprovideresearch,educational informationandotherservicesonlytoindividualsandinstitutionsthatfunctionwithoutregardtorace,color,sex,age,handicap,ornational origin.Forinformationonobtainingotherextensionpublications,contactyourcountyCooperativeExtensionServiceoffice. FloridaCooperativeExtensionService/InstituteofFoodandAgriculturalSciences/UniversityofFlorida/JohnT.Woeste,DeanChoosingSunglasses1 MaryN.Harrison2Sunglassesareanimportantconsiderationfor thoselivingintheSunshineState.Daysarelongand thesunisbright.Forpeoplewhospendtime outdoors,particularlyaroundwaterandsand, sunglassesareamust.Manydriversdependon sunglassestoovercometheglarefromthehighway andothersurroundings. Inthe1920s,militaryaviatorsdonned green-tintedglassestocopewithhighaltitudeglare. Atfirsttheideacaughtonslowly,butsoonit accelerated,andnowmostpeopleareawareofthe needforsunglasses. Sunglassesarenowconsideredafashionitemas wellasafunctionalone.Well-knownentertainers andpeopleofwealthusesunglassesasadisguise. Advertisersequatetheuseofsunglasseswith glamour.Highpricedsunglassescarrythenameof prestigiousfashiondesigners.(Forexample,which areyoumorelikelytofindonthemarket,sunglasses byLizClayborneorbytheMayoClinic?) Asthepublicbecomesmoreawareof,and concernedabout,thelong-termeffectsofover exposuretosunshine,anewmarketingapproachis beginningtoappear.Thenewemphasisisonthe performanceofsunglasses. Somesunglassesclaimtoprotecttheuserfrom ultravioletlight.Othersclaimtoblocktheblue segmentofvisiblelight,invisibleinfraredraysora combinationofthese.SUNLIGHTANDVISIONSunlightcontainslightraysofvaryingwavelengths. Someofthesearevisibletotheeyeaslightwhile othersarenot.Wavelengthsaremeasuredin nanometers(billionthsofameter).Theshortest wavelengthsarebelievedtobethemostdangerous. Studiesindicateultravioletlight(UV)doesthemost damagetotheeye,andespeciallythebandknownas UVB,whichincludestheshortestwavelengthsoflight reachingtheEarth'ssurface.Althoughthelonger wavelengthsoftheUVban,(calledUVA)cando damage,theyarelessdetrimentalthantheUVB. Thehumaneyehasatransparentcoveringover theiris(coloredpartoftheeye)andpupil(dark centerofeye).Thiscoveringiscalledthecornea. ThecorneaabsorbstheUVrays.Itissusceptibleto damagefromUVBandespeciallyfromwavelengths shorterthan295nanometers. Thecornea,undernormalconditions,canrepair damagetoitselffromUV.However,whensubjected toprolongedexposureunderbrightconditions,it cannotadequatelyprotectitself,andrecentstudies indicatethelenscanbedamaged. Thiscanresultinsometypesofcataracts (cloudingoflensthatinterfereswithvision).Thelens actsasafilterabsorbingalltheUVAandanyUVB notblockedbythecornea.Itprotectsthelight sensitiveretinaatthebackoftheeye.Somemedical authoritiesnowbelievethatexposuretobrightlight overmanyyearsmayagetheretinaandcontributeto 1.ThisdocumentisFactSheetHE5200,aseriesoftheHomeEconomicsDepartment,FloridaCooperativeExtensionService,InstituteofFood andAgriculturalSciences,UniversityofFlorida.Publicationdate:October1991. 2.MaryN.Harrison,professor,ConsumerEducation,HomeEconomicsDepartment,CooperativeExtensionService,InstituteofFoodand AgriculturalSciences,UniversityofFlorida,GainesvilleFL32611.

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ChoosingSunglasses Page2thedevelopmentofmaculardegeneration,adisease thatcausesblindnessinolderpeople. In1986,theAmericanNationalStandards Institute(ANSI)developedvoluntarystandardsfor manufacturersofnon-prescriptionsunglasses.There arethreetypes:cosmetic,general-purpose,and specialpurpose.Thestandardincludedlimitsonthe transmissionofUVBandUVA.Theyare: Cosmeticglassesmustblockatleast70percentof theUVB. Generalpurposemustblock95percentofthe UVBandmostUVA. Specialpurposemustblock99percentofthe UVBandmostUVA.(Forskiing,mountain climbingandotheroutdoorsports.) Therehavebeenanumberofcasesofpermanent damagetotheretinaofpeoplewhohavestaredat solareclipseswithouteyeprotection.Foryears scientiststhoughtthisdamagewascausedbyinfrared rays,alongwavelengththatproduceswarmthandis foundinvisibleandinvisiblelight.Somesunglasses claimtoblockinfraredrays. Recentresearchhasfoundinfraredraysare relativelyharmlesstotheeye.Thedamagefrom viewingasolareclipseresultedfromphotochemical damagetotheretinaandiscausedbytheshorter wavelengthofvisiblelight,theblueendofthe spectrum.Thishascausedsomescientiststobecome concernedoverthelong-termoutdoorexposureto bluelight.Somecompaniesnowpromotesunglasses thatfilteroutbluelight.Thesetypesofglassesare notnewhowever.Mostareamberglassesusedby boatersandhunterstoincreasevisibilityinablue haze. Todaysunglassesaretreatedwithachemicalto absorbUVrays.WhenvisiblelightandUV wavelengthsarereduced,soisthebluelight.Tests onsunglassesindicatethatanysunglassesthat blocked75percentofthevisiblelightadequately reducedthebluelight.TYPESOFSUNGLASSESSunglassesareavailableinawiderangeoftypes andprices.Almostallofthesunglassesmarketed todayprovideadequateeyeprotection.Thequality ofprotectionfromUVhasimprovedgreatlyoverthe pastfewyears.TheFDAhasimpactstandardsfor eyewear,sosunglassesdonotbreakeasily,anddonot poseasafetyhazard. Mostsunglassesmanufacturedtodayhaveplastic lenses.Thisenablesthelensestobelightinweight, toughinstrength,andresistanttobreakage.Most plasticlenseshavethecoloraddedasaningredientof theplastic.(Whencolorisaddedasacoating, scratchescanruinthefinish.) Polycarbonateplasticisusedforsomesports sunglasses.Itisquitetoughbutitwillscratchfairly easily.Polycarbonatelensesshouldhavea scratch-resistantcoating. Therearesixgeneraltypesofsunglasslenses: Plainlensesareconsistentincolor(novariation). Theyareavailableinavarietyofcolors. Dependingonthecolor,mostscreenoutfrom60 to97percentofthelight. Polarizedlensesareconstructedbysandwiching thepolarizingmaterialbetweentwolayersof plasticorglass.Becauseofthisunique composition,polarizedlenseseliminatetheglare reflectedfromflatsurfacesatspecificangles. Theyhelpcutreflectedglarefromsurfacessuch aswater,pavementandflatbeaches. Photochromiclensesaremadeofalight-sensitive materialthatdarkensautomaticallywhenexposed tooutdoorsunlightandlightensinsubdued indoorlight.Althoughresponsespeedhas improved,itstilltakesaboutfiveminutesforthe lensestolightenandaboutone-halftoaminute forthemtodarken.Thelensesaretemperature sensitive,darkeningmoreincoldweatherthanin hot.Ifusedfordriving,rememberyouaresitting intheshadedcar,notthedirectsunlight. Mirroredorflashlenseshaveathinreflective coating.Thecoatingcanbeofanycolor.Ifitis mirrored,thecoatingisathinsilvercolored metalliccoating.Thecoatingcanbeeasily scratched.Theselensesdonotofferanyspecial advantageoverothertypesoflenses. Gradientlensescanbeeithersinglegradientor doublegradient.Asinglegradientlensisdarker atthetopandlightertowardthebottom.This typecouldbehelpfulwhendrivingsincethedark topcouldgiveprotectionfromasunlithighway.

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ChoosingSunglasses Page3Thelightbottomofthelenswouldmakeiteasier toseethecar'sinstrumentpanel. Adoublegradientlensisdarkeratthetopand bottom,andlighterinthemiddle.Whengradient lensesareusedthefluctuationinlightingcanbe anadvantageinsomesituationsbutannoyingin others.COLOROneimportantconsiderationforsunglassesis color.Neutralgrayandsagegreenarethemost desirableandeffectiveforprovidingprotectionfrom glareandradiationwithoutdistortingthecolor sensitivityofyoureyes.Youareabletoseeitemsin theirtruecolors.Othercoloredlenseschangethe tintofthingsyousee.Amberlensesaresometime promotedtofilteroutbluelight.However,the ambercolorchangesthecolorofitemsviewed throughtheglassesandbluelightcanbereducedby otherways. Colorrepresentsapersonalchoice.Thereis nothingwrongwithchoosingacolorthatchangesthe tintofobjectsviewed,ifyouwish.DARKNESSOFLENSESThedarkerthelenses,thesmallertheamountof lightthatenterstheeye.However,mostlensesnow onthemarket,regardlessofpricehavebeentreated toabsorbUV.Therefore,thedarknessofthelenses shouldbeselectedforcomfortoftheindividualuser. Ifthesunglassesaretobeworninbrightsunshine, thelensesshouldbequitedark.Iftheglassesareto bewornwherelightisnotasbright,amedium-dark lenswouldbemoredesirable.UVPROTECTIONWhenaconsumerorganizationconducted laboratorytestson180pairsofsunglassestoevaluate theireffectiveness,itfoundmostofthesunglasses testedmetANSI'sUVBstandardforspecialpurpose glasseseventhoughtheywerebeingsoldasgeneral purpose.SomevariationwasfoundintheUVA blockagehowever,98.9percentreducedUVAas muchasthevisiblelightwasreduced.(Example,if visiblelightwasreduced75percent,UVAwas reduced75percent.)Mostofthe180pairsof sunglassestestedreducedUVAby90percentor more.COSTSSunglassesvarywidelyincost.Thereappearsto benostrongcorrelationbetweencostandquality. Also,costisnoindicatorofUVprotection.Almost allsunglassesprovideUVprotection. Thereissomecorrelationbetweencostand labelinginformation.Theleastexpensivesunglasses, especiallythosecostingunder$10,rarelycontain labelinginformation,exceptcountryoforigin.The medium-pricedglassesusuallycontainsome information(butnotalways),whilethemore expensiveonesusuallycontainconsiderable information. Aswouldbeexpected,inexpensivesunglasses usuallycomewithoutacase,whilemoreexpensive oneshaveapaddedcase. Asageneralrule,moreexpensivesunglasseshave betterconstructedframes.However,thereis variationandthemostexpensiveglassesdonot consistentlyhavebetterframesthanthosesellingata lowerprice.Forexample,theframeofglassesselling for$75isusuallybetterthantheframeofa$4.50 pair;itmaynotbebetterthantheframeofa$25 pair. Thepricetagisoftendeterminedbythenameon thelabel.Designernamesusuallycarryahigher pricetagthansimilarglassesoflessprestigious brands.Itpaystocomparisonshopforsunglasses. Oftentherearewidevariationsinthepricescharged bydifferentmerchantsforthesameglasses.DECIDINGWHICHTOBUYSunglasses,justaseyeglasses,aredefinedbythe FoodandDrugAdministration(FDA)asamedical device.Theyarerequiredtobeimpactresistant(not breakeasily),andtobesafeandeffective. Therearevoluntaryindustrystandardsthat recognizetypesoflenses.Manufacturersarenot requiredtoadheretothesestandards,butare encouragedtodoso.Unfortunately,labelingand advertisingmakeverylittleoftheinformationon standardsavailabletotheconsumer.Youareleftto findyourownwayofjudgingqualityandtypes. Pricerangesarenothelpfulindeterminingwhich sunglassesarebetterquality.Highpricesareoften

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ChoosingSunglasses Page4chargedfordesignerandcosmeticfeaturesinsteadof quality. Selectyoursunglassescarefullybecausethey affectyourvision.Thinkabouthowyouplantouse theglassesandyoursensitivitytoglareandbright sunshine.Peopledifferintheirtolerancetobright light,andintheiroccupationalandrecreational activities.Peoplewhoareinthesunshineorunder brightlightsusuallyneedsunglassesmorethanthose whodonothavethisexposure.Generallyaperson shouldwearsunglassesifbotheredbywateryeyes, squintingorconsiderableblinkingwhenout-of-doors. InFlorida,itiswisetowearsunglasseswheninthe brightsunshine. Lensesshouldbefreeofdistortionand imperfections.FDAandtheAmericanOptometric Associationsuggestasimpletesttocheckforthe refractionquality. Holdtheglassesatarm'slength.Lookata straightlinesuchastheedgeofdoororitsframe, whileslowlymovingtheglassesacrosstheline.If thestraightedgeappearsdistorted,orsways, curvesormoves,thelensisnotopticallyperfect. Bothlensesinapairofsunglassesshouldhave thesamecoloring.Holdthelensessothatyou canseethroughthemclearly.Checktoseeifthe coloringiseven,andneitherlensisdarkerthan theother.Forgradientlenses,makesurethe coloringlightensgraduallyinthesameareasof bothlenses. Theframesofsunglassesshouldbelarge,sturdy andfreeofroughspots.Thetemplesshouldnot blocksidevision.Framesshouldbecomfortable, yetfitcloseenoughtostayinplace.Testthe glassesbyputtingthemonandloweringyour head.Theglassesshouldremaininplace. Sometimestemplescanbeadjustedforbetterfit. Thelensesshouldbelargeenoughtocoverthe eyearea. Comparisonshopforsunglasses.Inspectdifferent brandsandvisitmorethanonestore.Ifsunglasses areinexpensive,youshouldinspecttwoorthreeof thesamebrand.Someglassesontheshelfmaybe bentoutofshapeorscratched.TIPSWearyoursunglasseswheninthebrightsunshine. Thiswillprovidecomfortandprotectyoureyesfrom UV.Also,somestudiessuggestexposuretobright sunwithoutprotectioncandecreasenightvision. Handleyoursunglasseswithcaretoavoid bendingandscratching. Keepyoursunglassesclean.Washwithamild soapandwateranddrywithasoft,lintfreematerial.REFERENCESBaushandLomb, SunglassesandYourEyes, Rochester,NY. ConsumerUnion,"Sunglasses," ConsumerReports Boulder,CO.8/88. FDA,"Sunglasses,They're'Cool,'TheyProtect," HaroldHopkins, FDAConsumer,Washington, DC.6/82.