Absorptive lenses

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1. Absorptive lenses
BY: ASMAA J.
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2. Absorptive lenses
•Absorptivelensesaretintedlensesthatimproveaperson’svisual
claritybyreducingglareandincreasingcontrast.
•Classification:
Absorptivelensesareclassifiedbytwovariables:
1.thetintofthelensitself
2.thelenstransmission
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Examples:
32% medium gray
10% medium amber
2% dark gray-green
20% medium plum
65% yellow
49% orange
16% amber
52% light orange
•Thenumberreferstothe
amountoflightpassing
through
•Thecolorreferstothe
tint

3. Absorptive lenses
•Themainadvantagesandfunctionsoftheabsorptivelensthatit
canprotecteyefromultravioletrays,filteroutexcesslightand
transmitonlyacertainamountofvisiblelightthroughthelens.
•Tintismorecomfortableinplasticthantheglassbecausetintin
glassisvariedfromareatoarea.(Inhighminuslenstintismore
inperipheralcomparedtocentralandviceversawithhighplus
lens)
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4. Types of the Absorptive Nature
1.Anti-reflectivecoating(ARC)
2.Anti-fogcoating
3.Mirrorcoating
4.Edgecoating
5.Photochromiclenses(Transitionlenses)
6.Polarizedlenses
7.Customtintsandcolors
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5. 1.Anti-reflectivecoating(ARC)
•Itisdielectricthinlayeranditisappliedonthesurfaceofthelensto:
(1)reduceunwantedreflectionsfromthelenssurface
(2)increasetheamountoflightthatpassesthroughthelenstotheeye.
•Themainproblemthattheitisbrittlenessandscratcheasily
•FinescratchesoftenaremorevisibleonARClensesthanonuncoated
lenses
•Withhighrefractiveindexlens,ARCmaterialmustalwaysbeused
•ThebestsolutionforheadlightglareatnightisanARCprescription
•ARCmadeofmetalsoxidesuchasmagnesiumflorideandsiliconnitride
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6. 6
Reflectionsofspectaclelenses
thatmaycausetroublesometo
thewearer.
Thereflectioncouldoccuronthe
frontorbacksurface,orevenan
internalreflectionandcorneal
reflection

7. 1.Anti-reflectivecoating(ARC)
Advantages:
₋Theyimproveyourvisionbyreducingreflections,glare,andhalos
₋Theycanprovidecomfortduringcomputerandmobileuse(buttheydon't
preventallglareandlight,whichmaycauseeyestrainorheadacheswith
prolonguseofscreens)
₋Theyallowmorelighttoreachyoureyes,improvingvisualacuity
₋Theycanreducetheeffectsandsymptomsofdigitaleyestrain
₋Theymakeyoureyesmorevisiblebehindyourlenses
₋Theyprovidelessglarewhendrivingatnight
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8. 1.Anti-reflectivecoating(ARC)
•AstandardARcoatingistypicallycomprisedoftwolayers:
1.Anti-reflective
2.Scratch-resistant
•PremiumARcoatingshavemultiplelayers,suchas:
1.Improvedscratchresistance
2.Hydrophobic:Anti-water
3.Oleophobic:Reducesfingerprints
4.Anti-static:Repelsdust
5.UVprotection
6.Bluelightprotection:Protectsyoureyesfromharmfuleffectsofdigital
devices
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11. 2.Anti-fogcoating
•Prescribedtowearerwhohastomoveindifferenttemperaturewith
spectacle
•Antifogcoatingismadeupof‘resinfilm’
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Resin film

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3.Mirrorcoating
Thiscoatingisappliedontheanteriorsurfaceofthespectaclelens
Itismadeupofmetalizedanddielectriccoating
Theuseofthemirrorcoatingonthespectaclelensmaketheobservernot
abletoseethewearereyes
Mirror coating

13. 4.Edgecoating
Herecolourisappliedatthebevelareaofthelenstoreducetheconcentric
rings
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Lens bevel coating

14. 5.Photochromiclenses
•They’rethetypeoflensthatchangestoa
darkercolorautomaticallywhenexposedto
thesunorothersourcesofUVlight
•Itchangestheamountofthelight
transmission
•Incaseofglasslens‘silverhalidecrystal’is
used,andincaseofplasticlensorganicdyes
areused
•Ingeneral,theselensesworkbyusing
chemicalreactionsthataretriggeredbyUV
exposure.Theresultofthechemical
reactionisacolorchangeinthelens
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15. 5.Photochromiclenses
Advantages:
⁻Canbeusedindoorsandoutdoors
⁻TheyoffercontinuousUVprotection
⁻Theycansaveyoumoneyandtheyarepermenent
⁻Theyreduceheadacheandeyestrain
Disadvantages:
⁻Youcannotcontrolthetransmissionandthedarkenamount,somelenses
alsotakelongerthanotherstoadjusttobrightness
⁻Theselensescantakelongertoadjustincoldweather
⁻Theydon’tdarkenwellinsidecarsbecausecarsglasscontainUVprotection
⁻Theydon’tprotectfrombluelight(someofthemcontainanti-bluelight)or
Infrared(IR)radiation
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16. 6.Polarizationlenses
•Polarizedlenseshaveaspecialchemicalappliedtothemtofilterlightand
thatblockcertainvibrationoflightwaves.
•Mainlypolarizedlensisusedtocuttheglareandblocktheultraviolate
rays.
•Onpolarizedsunglasses,thefiltercreatesverticalopeningsforlight.Only
verticallightcanpasstotheeyes,andthehorizontallightwillbeblocked.
AndtheyalsoblocktheUVray(butnotallofit).
•Asaresultofthisfiltering,theimagewillbeabitdarkerthanusual,but
sharperandclearer.
•Theyarehelpfultoreduceeyefatigue,reduceglare,andtheyincrease
visualclarityandcomfort.
•Ifthewearertiltshisorherhead,thepolarizedlenswillnotwork.
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18. 6.Polarizationlenses
•Whentouse:
⁻Fishingandboating
⁻Snowingenvironment(Althoughsnowtendstoreflectlightequallyin
alldirections,sothislenswillnotbeveryeffective)
•WhenNOTtouse:
⁻WithLCDscreen(Cellphones,cardashboard,ATMmachine…)
⁻Nightdriving
⁻Pilotscannotuseit
⁻Whenyouareworkingwithcolours(especiallywhite)
⁻Workingwithheavymachines
⁻Itisdangerouswithskiing
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20. 7.Tintsandcolours
•Acolourtintcanenhancethevisualperformanceofspectaclesforcertain
sportsoractivities.
•Tintingdonebydifferentmethods:
1.Surfacecoating:mostlyusedwithglasslens.
2.Dyetinting:mostlyusedwithplasticsbyplacingthelensonadyebath.
•Thetintispermanent,butitcouldbecomedarkerorlighter
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21. 7.Tintsandcolours
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•GoodabsorptionforthegreenglasslensinboththeIRandUVregions
•Bestforsomesportssuchasgolfandtennis
•Helpsinbrightshadow
•Mostpopularforsunprotection
•Naturalcontrastinmid.tohighsunlightandprovidetruecolorperception
•EqualtransmissionthroughthewholevisiblespectrumThischaracteristicallows
colorstobeseenintheirnaturalstaterelativetooneanother
•Goodchoicefordriving
•Usefulforphotophopia
•Increasecontrastinhazy,foggy,orlow-lightconditions,andinsnow
•Filtersthebluelightwithoutreducingtheluminance

22. 7.Tintsandcolours
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•Brightfluorescentlightingorglareintheworkarea
•Increasecontrastbyblockingbluelight
•Redfilterisveryhelpfulfor(Retinitispigmentosa)
•Ahigherabsorptionofshortervisiblewavelengths
•Improvecontrastonbright
•Enhancecontrast
•Hazy,orsmoggydays
•They'reusefulagainstgreenandbluebackgrounds,likegrassandsky
•Veryusefulwiththosedisease(Developingcataracts,Aphakesandpseudophakes
Maculardegeneration,Cornealdystrophy,Opticatrophy)
•Darkbrownisusefulforphotophobia

23. Sunglasses:
•Theidealpairofsunglassesshoulddothefollowing:
1.Reducetheintensityofsunlight
2.Visualcomfortandvisualperformance
3.Eliminatepartsoftheopticalspectrumthatarenotrequiredforvisionandare
hazardoustotheeyes
4.Provideenoughprotectionandreduceglare
5.Maintainnormalcolorvisionandallowthewearertodistinguishtrafficsignalsquickly
andcorrectly
6.Resistimpactandscratchingandonlyrequireminimumofcare
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24. Lens Caring
1.Rinsefirst,itisbettertousewarmwater(drycleaningmay
causescratches)
2.Youcanuseanalcohol-freelenscleaningsolution(dropofdish
detergentcanwork),donotusesaliva,ammonia,ornormal
windowandmirrorcleaners
3.Wipewithalintfreemicrofibercloth
4.Putthespectaclewiththeframeup
5.Avoidtouchingthelenses
6.Avoidwearingglassesduringsportsandtoughactivties
7.Keepthemintheircases,notdirectlyinyourbagoryourpocket
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1. Rinse
4. Don’t touch the lens
2. Use alcohol free cleaner
5. Put the frame up
3. Use the lens cloth
6. Remove during sport