Evolution of Diffractive Multifocal Evolution of Diffractive Multifocal Intraocular Lenses Intraocular Lenses Wavefront Congress Wavefront Congress February 24, 2007 February 24, 2007 Michael J. Simpson, Ph.D. Michael J. Simpson, Ph.D. Alcon Research, Ltd., Fort Worth, Texas Alcon Research, Ltd., Fort Worth, Texas
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Evolution of Diffractive Multifocal Intraocular Lensesvoi.opt.uh.edu/VOI/WavefrontCongress/2007/presentations/... · 2007-03-08 · Evolution of Diffractive Multifocal Intraocular
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Evolution of Diffractive MultifocalEvolution of Diffractive MultifocalIntraocular LensesIntraocular Lenses
Early Diffractive multifocal IOLEarly Diffractive multifocal IOL full-optic, equal energyfull-optic, equal energy rigid, meniscus, strong loops (it is not just the optics)rigid, meniscus, strong loops (it is not just the optics)
Diffractive: Light goes into both distance and near powers from all zones
Diffractive Multifocal LensesDiffractive Multifocal Lenses Physical geometry is very importantPhysical geometry is very important
Place zone boundary where optical distancePlace zone boundary where optical distanceto image increases by 1 wavelengthto image increases by 1 wavelength
Create optical jump in phase at boundaryCreate optical jump in phase at boundary Zones shaped to direct lightZones shaped to direct light Light from all zones goes to both imagesLight from all zones goes to both images Adjacent zones have Adjacent zones have
similar effectssimilar effects
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Full-optic Equal-Energy Diffractive IOLFull-optic Equal-Energy Diffractive IOLTheoretical Energy Balance at 550 nmTheoretical Energy Balance at 550 nm
81% theoreticalmaximum
constant diffractive steps heights across entire lens
distance and near ~ 41 % for all pupils
additional energy goes to higher diffraction orders
steps only ~ 1-2 microns
• Rigid PMMA lenses•6mm diameter, large incision
• Meniscus optic shape• meniscus lenses no longer used
•Closed-loop and long haptics• large force on capsule
More recent Full Optic Equal-Energy Diffractive More recent Full Optic Equal-Energy Diffractive IOLsIOLsLenses with published clinical dataLenses with published clinical data
Full Optic Full Optic UnUnequal-Energy Diffractive equal-Energy Diffractive IOLsIOLs
Changing the step heights changes the energyChanging the step heights changes the energy lower steps send more light to distancelower steps send more light to distance higher steps send more light to nearhigher steps send more light to near all zones have the same optical effectall zones have the same optical effect
““Distance dominantDistance dominant”” or or ““Near dominantNear dominant””
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n) Equal dEqual n70/30 d70/30 n
Full Optic Full Optic UnUnequal Energy Diffractive equal Energy Diffractive IOLsIOLs
shorter steps send less light to near
taller steps send more light to near
Diffractive step heights control the energyDiffractive step heights control the energy Total energy for the two powers typically ~81%Total energy for the two powers typically ~81%
distance energy for shorter steps; near energy for taller steps
near energy for shorter steps; distance energy for taller steps
Full Optic Full Optic UnUnequal Energy Diffractive equal Energy Diffractive IOLsIOLs
Energy balance sometimes given just for primaryEnergy balance sometimes given just for primarypowerspowers portion of total energy not always givenportion of total energy not always given e.g. 70%:30% e.g. 70%:30% distance:neardistance:near energy, energy,
•• actually 57% distance, 25% near at design wavelengthactually 57% distance, 25% near at design wavelength
IOL examples are IOL examples are AdatomedAdatomed, , Acri.TwinAcri.Twin, and, andAcri.LisaAcri.Lisa IOLsIOLs foldable diffractive lensesfoldable diffractive lenses biconvexbiconvex asphericaspheric sloped diffractive steps for sloped diffractive steps for Acri.LisaAcri.Lisa
Limited published clinical dataLimited published clinical data
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Limitations of Full Optic Diffractive Limitations of Full Optic Diffractive IOLsIOLs
Near vision rarely used for large pupilactivities, and the near componentcreates a halo effect for distance visionwith large pupils
Most large pupil activitiesinvolve distance vision
The maximum energy in thetwo images is about 81%
Theoretical relative energy at design wavelength between distance and near
Apodized Diffractive Surface and Energy BalanceApodized Diffractive Surface and Energy Balance
ReSTOR use of Apodization toReSTOR use of Apodization toControl Defocused LightControl Defocused Light
The ReSTOR Apodized Diffractive OpticThe ReSTOR Apodized Diffractive Optic
Diffractive zones are in same locations as for full-Diffractive zones are in same locations as for full-optic diffractive IOLoptic diffractive IOL zone location determined by zone location determined by ““AddAdd”” power power
Apodized diffractive structure blends into peripheralApodized diffractive structure blends into peripheralrefractive regionrefractive region
Matches optical properties to visual needsMatches optical properties to visual needs Reduces nighttime visual phenomenaReduces nighttime visual phenomena Increases overall percentage of light usedIncreases overall percentage of light used
Diffraction divides light between two powersDiffraction divides light between two powers Diffractive step heights control the energy balanceDiffractive step heights control the energy balance Apodized diffractive IOL has gradual change inApodized diffractive IOL has gradual change in
step heightsstep heights central distance/near vision regioncentral distance/near vision region outer outer ““refractiverefractive”” distance vision region distance vision region allocates appropriate light energy according to activityallocates appropriate light energy according to activity
and light levelsand light levels designed to minimize photic issuesdesigned to minimize photic issues high level of spectacle independencehigh level of spectacle independence