Energy balance in apodized diffractive multifocal ...

$: Energy balance in apodized diffractive multifocal ...$
Energy balance in apodized diffractive multifocal intraocular lenses

Francisco Alba-Bueno*a, Fidel Vegaa, María S. Millána

a Optics and Optometry Department, Polytechnic University of Catalonia.

ABSTRACT

The energy distribution between the distance and near images formed in a model eye by three different apodized diffractive multifocal intraocular lenses (IOLs) is experimentally determined in an optical bench. The model eye has an artificial cornea with positive spherical aberration (SA) similar to human cornea. The level of SA upon the IOL, which is pupil size dependent, is controlled using a Hartmann-Shack wave sensor. The energy of the distance and near images as a function of the pupil size is experimentally obtained from image analysis. All three IOLs have the same base refractive power (20D) but different designs (aspheric, spherical) and add powers (+4.0 D, +3.0 D). The results show that in all the cases, the energy efficiency of the distance image decreases for large pupils, in contrast with the theoretical and simulated results that only consider the diffractive profile of the lens. As for the near image, since the diffractive zone responsible for the formation of this image has the same apodization factor in the spherical and aspheric lenses and the apertures involved are small (and so the level of SA), the results turn out to be similar for all the three IOL designs.

Keywords: intraocular lens, multifocal lens, diffractive lens, imaging efficiency

1. INTRODUCTION The crystalline lens in the eye provides the ability of focusing objects at different distances in a process called accommodation. This lens grows throughout life and increases in size and rigidity, causing the loss of the accommodation capacity (presbyopia) around the 45-50 years and later the loss of transparency (cataracts). Cataract is the most common cause of visual impairment in the world [1]; the surgical treatment of cataract involves the extraction and replacement of the crystalline by an intraocular lens (IOL).

Nowadays the implantation of diffractive multifocal intraocular lenses (DMIOLs) is a common procedure intended to avoid the spectacle dependence in near vision. The DMIOLs uses the base lens curvature and the zero (m=0) and first (m=1) diffraction orders to achieve two focal points (often referred as to optical powers) that corresponds to the far and near foci respectively [2], [3]. These designs allow the pseudophakic eye to correctly focus at different distances but have an inherent drawback: the focused retinal image formed by one of the powers of the DMIOLs is always overlaid by an out of focus image from the other lens power. This effect may lead to visually disturbing phenomena such as halos and/or glare perceptions [4] depending on the illumination conditions, the axial distance between the two images and their relative energy distribution. For these reasons, the contrast sensitivity in eyes implanted with DMIOLs may be worse than those implanted with monofocal IOLs [5]. To fully understand the nature of these effects it is interesting to characterize in a test bench [6] the optical performance of these IOLs. The Point Spread Function and Modulation Transfer Function are metrics widely used in other works to characterize the optical quality of different IOLs [7][8]. It is less common, however, to analyze the energy distribution between the distance and near images and its variation with the pupil diameter. The energy distribution is an optical quality feature that is especially important in the case of the apodized diffractive multifocal intraocular lenses (ADMIOLs) like the AcrySof® ResTOR® (Alcon, Fort Worth, Texas, USA), which are specifically designed with a twofold purpose: to reduce the glare and halo phenomena and, in addition to this, to have an increasing distance-dominant behavior for large pupil sizes. The latter implies to make the energy distribution between the distance and near images dependent on the eye pupil. Furthermore, some of these IOLs have aspheric surfaces, and there is a great interest to determine in a test bench [9][10] and in clinical studies [11][12][13] the advantages of this design versus the spherical one, particularly when some studies have shown little or no benefit of aspheric IOLs operating with small pupils [13][14].

In this work the energy balance between distance and near images of ADMIOLs of different design (aspheric, spherical) and add powers (+4.0 D, +3.0 D), is experimentally obtained as a function of the pupil size in a test bench. The * [email protected] Tel 937398678 Fax 937398301

22nd Congress of the International Commission for Optics: Light for the Development of the World,edited by Ramón Rodríguez-Vera, Rufino Díaz-Uribe, Proc. of SPIE Vol. 8011, 80119G

2011 SPIE · CCC code: 0277-786X/11/$18 · doi: 10.1117/12.902895

Proc. of SPIE Vol. 8011 80119G-1

experimental aim to study naturally induwould really

2.1 Intraocu

The ADMIO6mm diametecovers the cenorders that csends light tolatter being incorneas [17][pupil [19]. The radii of tthe add powe

where i is theand Dadd= +3The height hapodization f

for which the where h0 is thbetween the Ithe lens is imparts of the dunits) is:

with hi

calcu

Figure 1. z

results are cothe performanuced by a humimprove the I

ular lens desc

OLs AcrySofer with a hybntral 3.6mm o

correspond to o the distance ntended to in[18]. This com

the diffractiveer [20]:

e zone numbe3.0D, the radiuhi of the difffactor is given

e step height re

he maximum IOL material

mmersed. Becdiffractive pro

ulated with Equ

Left: Image andzone.

ompared to thnce of these Aman eye. The OL performan

cription and t

f® ResTOR®

brid diffractiveof the lens andthe distance afocus exclusiv

ntroduce negatmpensation, e

rings (and th

ri2 = 2i −1( )

er, λ is the desus of the centrffractive steps

by Lee et al:

fiapodized = 1

eduction is givhi = f apodized

height at the (refractive inause of the refile are phase

α i = nIOL −(uation (3).

d dimensions o

e theoretical pADMIOLs in final goal is t

nce.

2.theoretical en

are describee-refractive ded diverts lightand near foci,vely. The antetive SA and texpressed by m

us the number

)λ 1000Dadd

,

sign wavelengral disk is r1=0s smoothes to

−ri

router

⎛

⎝⎜⎞

⎠⎟

2 fven by: d ⋅ h0 , optical axis (dex nIOL=1.55efractive indee shifted by di

naqueous)hiλ

f one of the me

predictions tha model eye to determine w

. METHOnergy balance

ed in detail inesign on its at simultaneous, respectivelyerior base surfthus, to partiameans of the

r of diffractiv

gth, and Dadd0.428mm wheowards the p

for ri = 0,r1,

(r=0). The dif5) and the aqux difference nifferent amoun

,

easured ADMIO

at only considthat induces Swhether the a

OD e

n Refs. [15][1anterior surfacsly into the ze. The outer reface of the lenally compensa

c[4,0] Zernik

ve zones) are d

is the add powereas it reduceperiphery (apo

,r2,...,router ,

ffractive profiueous mediumnIOL-naqueous, thnt. The maxim

OLs. Right: Ske

der the diffracSA values upo

aspheric design

16]. These lence (figure 1, lero (m=0) anegion of the IOns may be eithate for the natke coefficient

determined by

wer (in Dioptes to r1=0,371modizing profi

ile of the lens m (refractive ihe light wave

mum induced

etch of the apod

ctive profile oon the IOL sin or a particu

nses have an oleft). The diffnd first (m=1OL is purely

her spherical otural positive t is 0.20µm fo

y the design w

(1)

ters). Thus, fomm for Dadd=le in figure

(2)

(3) acts as an op

index naqueous=es passing throphase shift (in

(4)

dization of the c

f the lens. Weimilar to thoseular add power

optical zone ofractive region1) diffractionrefractive and

or aspheric, theSA of human

or a 6mm eye

wavelength and

or λ = 550 nm=+4,0D.

1, right). An

ptical interface=1.336) whereough differenn wavelengths

central

e e r

f n n d e n e

d

m

n

e e

nt s


By setting h0=1.3 µm [16] in Equation (4) the value of αi at the first diffractive zone is α0=0.51, which is close to half wave. The apodization of the diffractive profile of the MDIOLs implies that the value of αi progressively decreases from the center to the periphery of the diffractive zone, which has important implications on how the light is distributed between the m=0 (distance power) and m=1 (near power) diffraction orders as a function of the pupil aperture or, equivalently, as a function of the number of diffractive rings that are illuminated. If αi were constant for all the rings, the diffraction throughput efficiency (TE) of the m=0 and m=1 orders would be given by [21]:

TEm=0,1 = sinc2 (m −α i ) . (5)

However, since the value of αi varies with the radius, the TE for each αi (TEm=0,1i ) has to be weighted by a factor that

corresponds to the ith-diffractive ring area. Therefore, the energy that the diffractive part of the IOL would divert from an incident plane wave into the m=0 and m=1 diffraction orders is calculated by means of linear combinations of the weighted contributions of the rings:

Im=0diffractive = cte ⋅ Ai ⋅TEm=0

i

i=1

n

∑ , (6)

Im=1diffractive = cte ⋅ Ai ⋅TEm=1

i

i=1

n

∑ , (7)

where cte is a proportionality constant and n is the number of diffractive rings of area Ai that are illuminated and thus are taking part on the diffraction process. With a reduced pupil aperture for which the IOL only operates with the first diffractive zone (i.e., αi=α0 ) there is nearly equal diffraction throughput efficiencies for the distance (TEm = 0

0 = 0.38 ) and near (TEm =10 = 0.43 ) powers. With larger

pupils, more diffractive rings are illuminated but the progressive reduction of the phase shift of the waves <as they pass through the outer diffractive rings implies that TEm = 0

i > TEm =1i , and according to Equations (6) and (7) the energy sent to

the distance power (m=0) becomes reinforced at the expenses of the near power (m=1). In the case of the purely refractive region of the ADMIOL, the light goes exclusively to the distance power i.e. TEm = 0

refractive = 1 , and therefore the energy is simply: Im= 0

refractive = cte ⋅ Arefractive ⋅TEm= 0refractive , (8)

where Arefractive is the area of the illuminated refractive region of the ADMIOL. Then, the amount of energy sent to either the distance and near powers strongly depend on the size of the pupil or, equivalently, on the size of the illuminated area of the IOL (referred from now on as to IOL-pupil) and can be calculated as: Im= 0 = Im= 0

diffractive + Im= 0refractive , (9)

Im=1 = Im=1diffractive , (10)

which can be expressed in terms of energy efficiency as:

Im=0

I IOLtotal , (11)

Im=1

I IOLtotal , (12)

where I IOLtotal is the total energy transmitted through the whole IOL aperture. This energy is proportional to the area of the

IOL aperture AIOL provided that any loss of energy (for instance caused by scattering in the diffractive steps) [22] is neglected: I IOL

total = cte ⋅ AIOL . (13)


We have calcin the case oelsewhere [15pupil size. Thenergy balanc

Figure 2.

However, it amount of theenergy will bbase lens (eitturns out to dinserted in a impinging on The ADMIOSN6AD1. Thaspheric (SN6

Table 1. C

2.2 Optical b

To assess theoptical benchEntrance Puprequirements

Type

First surfac

Second surf

Base power

Addition (D

culated the eneof the AcrySo5][16] and shhus, for small ce changes in

Theoretical ene

must be empe energy sent

be properly focther aspheric depend on the

model eye wn the IOL with

Ls used in thheir characteri60WF) design

Characteristics o

bench

e real energy h sketched in Fpil-(EP)) the [25] except fo

SN60

Mon

ce Sphe

face Sphe

r (D) 20.0D

D) -

ergy efficiencof® ReSTOR®

ow that there pupils the enfavor of the d

ergy efficiency

phasized that to either the dcused onto theor spherical)

e type of the cwith an aberrah a value of SA

his study are tistics are showns will be also

of the IOLs stud

distribution bFigure 3 [6]. Tartificial corn

for the artificia

0AT

nofocal

erical

erical

D

cies according®. The results,

is a differentnergy is nearlydistance focus

of the distance

these calculatdistance or neae respective imwhere the di

cornea and theated cornea [2A that depend

the three Acrywn in Table 1o considered fo

died.

between distanThe IOL is innea and the wal cornea.

SN60WF

Monofocal

Aspherical

Spherical

20.0D

-

to Equations , plotted in Ft energy balany equally divi.

and near powe

tions do not ar powers for mages, the latffractive profe pupil size). 23][24] the las on the size o

ysof® ReSTO. Their mono

for the sake of

nce and near nserted in a mwet cell. The

SN60

Bifoc

SpheApodDiffr

Sphe

20.0D

+4.0

(11) and (12)ig. 2, are in ence between tded between t

ers in an ADMIO

take aberratioa particular IO

tter dependingfile is made, oThis fact is etter meaning of the pupil ap

OR® availableofocal counterf comparison.

images formeodel eye form model eye i

0D3

cal

erical - dized - ractive

erical

D

), as a functionexcellent agrethe two opticathe two foci w

OL of +4.0D of

ons into accoOL pupil, but g on several faor the level oespecially rele

that there woperture.

e in the markrparts with bo

ed by ADMIOmed by an iris is in accordan

SN6AD3

Bifocal

Aspherical Apodized - Diffractive

Spherical

20.0D

+4.0

n of the IOL-peement with tal powers depwhereas for la

f addition.

ount. They onthey do not e

actors like thef SA upon th

evant when thould be a con

ket: SN60D3, th spherical (

OLs, we havediaphragm (th

nce with the

SN6A

Bifoc

- AsphApodDiffr

Sphe

20.0D

+3.0

pupil diameterthose reported

pending on thearge pupils the

nly predict theensure that thise design of thehe IOL (whiche ADMIOL is

nverging beam

SN6AD3 andSN60AT) and

e designed thehat acts as theISO standard

AD1

cal

herical - dized - ractive

erical

D

r d e e

e s e h s

m

d d

e e d


Instead of uslens that induis important tSA produced

Figure 3. the d

We have simas a function US). This sim4.

Figure 4. artifiZern

2.3 Energy b

The energy danalysis as silluminates thcornea plus wseparated alocorrected micand magnify

sing an aberrauces an amounto realize thatby the artifici

Optical setup todistance and nea

mulated the depof the IOL-p

mulation has b

Black line: Calicial cornea (fus

nike c[4,0].

balance from

distribution betshown in Fighe 200μm pinhwet cell) wherong the opticacroscope mounit onto an 8-b

ation free artifnt of SA at thet the size of thial cornea upo

o implement a mar images that, i

pendence of thupil using com

been experime

lculated value osed silica; n=1.4

m image analy

tween the distg. 3. The quhole object. Are the IOL is ial axis. Thesented in a highit image acqu

ficial cornea ae IOL plane sihe EP determion the IOL.

model eye and tin turn, can be s

he SA of the wmmercial optientally verifie

of the Zernike c46 R1=39.53mm

ysis.

tance and nearuasi-monochroA collimator prinserted. Whee images areh precision tranuisition CCD c

as the ISO staimilar to that nines on one ha

test IOLs. A pinsequentially foc

wavefront thaical design sod using a Har

[4,0] SA coeffim; R2=-39.53mm

r images as a omatic LED roduces a colln an ADMIOreferred to asnslation holdecamera.

andard recomnaturally induand the IOL-p

nhole object at cused on the CC

at leaves the aftware (Zema

rtmann-Shack

icient as a functm; e=4.9mm). B

function of thwith a narrolimated beam L is tested, ths near and dier is used to se

mmends, we uuced by the hupupil and, on

infinity is imag

CD sensor.

artificial corneax Developme

wavefront se

tion of the IOL-Blue crosses: m

he EP diameteowband emiss

m that illuminahe pinhole objistance imageelect either the

use an equiconuman cornea [

the other han

ged by the DMI

ea and impingent Corporationsor and it is

-pupil diametermeasured value

er is obtained tsion centered

ates the modelect is imaged

es, respectivele distance or t

nvex spherica17][18][26]. I

nd, the level o

IOL into

ges on the IOLon, San Diego

shown in Fig

r of the of the

through imaged at λ=521nml eye (artificia

d in two planesly. An infinitethe near image

al It f

L o, g.

e m al s e e


Examples of in Fig. 5(a) anFig. 5) surrouoverlaying dethat strongly just in the foregions (Itotal=

where R standg(n) is the pixthe borders odetector, [27]is calculated a

Figure 5. to theback

In order to esit, we have stand asphericcorrespondingand Ipinh are nthat for both tenergy Ipinh ismatter the typorder of 80% For larger EPspherical SN6implies that, w‘wasted’ in th

the near and dnd Fig. 5(b), runded by blurefocused imagdepends on lecused pinhole= Ipinh+ Ibackg)

ds for either thxel grey level.f the region th]) was used toaccording to E

a) and b): Neare region named

kground.

stablish the rotarted studyin

c (SN60WF) g relative enenormalized to types of IOLss nearly the sape (spherical are obtained

P diameters a d60AT, the enewhen openinghe background

distance imagerespectively. Brred backgrounge. In the casevel of SA upe region (Ipinh), are obtained

IR =

he pinhole reg. Since the imhat correspon remove all thEquation (14)

r and distance imd pinhole (pinh)

3le of the SA u

ng the variatioIOLs. The r

ergies, definedthe value of

s and small IOame as Itotal, w

or aspheric) with small ap

different behaergy Ipinh remag the entrance d, and conseq

es of the pinhBoth images bnd or halo (lae of the dista

pon the IOL a), and the ene

d by integration

= g(n)n pixel

n∈R

∑

gion or the totmages are blurr

ds just to the he background

from these fil

mages experime) and backgroun

. RESULTupon the IOL n of the energ

results are pld as Ipinh/Itotal, aItotal obtained

OL-pupil diamwhich means th

of monofocalpertures for bo

avior between ains constant, pupil, most o

quently, a dram

hole object obtbasically consabeled Ibackg inance image (Fas it will be shergy of the totn of the pixel

tal image (R=pred because offocused pinho

d contributionltered images.

entally obtainednd (backg) resp

TS AND DIand how the

gies Itotal and Ilotted, as a fare plotted in with the larg

meters up to 3 hat the backgrl IOL is. As a

oth IOLs as it i

the spherical even though

of the additionmatic reductio

tained with ansist of the focun Fig 5). This ig. 5(b)), how

hown in the ntal image thatgrey level in

pinh, total), nf the backgrouole. An edge doutside the p

.

d with an ADMpectively. c) and

ISCUSSIOlens design (aIpinh obtained function of tFig. 7. To ma

gest pupil diammm (when thround contribua consequencis shown in Fi

and aspheric the measured al available en

on of the imag

n ADMIOL Acused image ofbackground c

wever, there isext paragrapht comprises ththe correspon

n is a pixel conund, it is not sdetection algoinhole (Figure

MIOL in the modd d): same as ab

ON aspheric vs. spwith the mon

the IOL-pupilake the compa

meter (6 mm).e level of SA ution is neglige, images of ig. 7.

IOLs can be Itotal increases

nergy is not sege efficiency o

crySof RESTOf the pinhole (corresponds prs an additionahs. The energyhe pinhole plunding regions:

(14)

ntained in thetraightforward

orithm (Sobel es 5(c) and 5(

del eye. The arrbove after remo

pherical) may nofocal sphericl diameter inarison of resu. The results iupon the IOL

gible in these high relative

observed. In ts (figure 6, lefent to the pinhoccurs (see Fi

OR are shownlabeled Ipinh inrimarily to theal contributiony of the imageus background

e R region, andd to determineedge gradien

d)). Then, Ipin

rows point ving the

help to tacklecal (SN60AT

n Fig. 6. Theults easier, Itotain Fig. 6 showL is small), theconditions, noenergy of the

the case of theft). This resulhole image buig. 7, left). For

n n e n e d

d e

nt h

e ) e al w e o e

e lt ut r


the aspheric smaller than diameters as i

Figure 6. diam

Figure 7. Righ

The results ob(Fig. 4) and twere little difthere are highThus, since t[24], more anOn the contraartificial cornalthough it ca The same typ(spherical SN(+4.0 D SN6Ain the case oADMIOLs: i

SN60WF, thethe increase oit is shown in

Energies Itotal meter. Left: Sphe

Energy efficienht: Aspheric des

btained with mthe IOL desigfferences in thher levels of Sthe spherical Ind more energary, the asphenea and manaannot impede

pe of measureN60D3 vs. aspAD3 vs. +3.0of the near imt increases sli

e larger the eof Itotal (Fig. 6Fig. 7, right.

and Ipinh measerical design. R

ncy (Ipinh/Itotal) asign.

monofocal IOgn. Thus, for she performancSA upon the IOIOL introducegy goes to the ric IOL show

ages to still foa certain redu

ements was capheric SN6AD

0 D SN6AD1)mages there ightly for IOL

entrance pupil6, right), whic

sured in the imaRight: Aspherica

as a function of

OLs can be exsmall IOL-pu

ce of the aspheOLs and the pes additional background f

ws a better perfocus a good amuction of the re

arried out in thD3) and in A. The results fis practically

L-pupil diame

l the larger thch implies a m

age plane of moal design.

f the illuminated

xplained takingupil diameters,eric versus theperformance opositive SA tfor larger pupformance becmount of the elative energy

he ADMIOLsADMIOLS wifor the distanc

y no differenceters up to ~3

he value of Ipmoderate redu

onofocal IOLs a

d diameter of m

g into accoun, when the effe spherical mo

of the IOLs is that adds to th

pils, which stroause it tends tadditional en

y of the image

s of the same ith the same ace and near imce between th.6 mm that co

inh, but the inuction of its re

as a function of

monofocal IOLs

nt both, the levffects of the Sonofocal IOL.very differenthe one produongly reducesto partially co

nergy in the pifor large pup

add power (+aspheric desigmages are plothe energy Ipinorresponds to

ncrease occurselative energy

f the IOL illumi

. Left: Spherica

vel of the SA A turn out to. For larger put depending onced by the ars its efficiencyompensate for inhole region ils (Fig. 7, rig

+4.0 D) but dign but differetted in Fig. 8 nh measured

o the diffractiv

s with a slopey for larger EP

inated

al design.

upon the IOL be low, thereupils howevern their designrtificial corneay (Fig. 7, left)r the SA of the

of the imageght).

ifferent designent add powerand show thain any of theve zone of the

e P

L e r, n. a ). e

e,

n r

at e e


IOLs and theincreases withas it is shown These resultsthe formationlevel of SA uenergy to theIOL-pupil diaconditions, thenergy efficie

Figure 8. ADM

It is in the casproduces somIpinh first increpupils. The rpupils are abosignificant diSN6AD1).

Figure 9.

Expressing thIOLs (spheric

en keeps a lowh the EP (see

n in Fig. 9.

are not unexpn of the near iupon the IOL (e near image, ameter and thhe aspheric deency, in front

Energies Itotal aMIOL as a funct

se of the distame differenceseases with theresults of the out 30% highfferences in th

Energy efficien

hese results incal and aspher

w constant val Fig. 8), the e

pected taking image corresp(Fig. 3). Onceand as a con

e particular deesign of the Sof the spheric

and Ipinh measuretion of the IOL

ance images ans in the experie EP diameteraspheric SN6

her than the vahe results obta

ncy (Ipinh/Itotal) a

n terms of the ric) behave ve

lue for larger energy efficien

into account ponds to the de the diffractivnsequence Ipinhesign (spheric

SN6AD3 or thcal design of th

ed in the near (rL illuminated dia

nd large EP diimental resultr (up to 3-4 m6AD3 IOL foalues measureained in the A

as a function of

relative energery similarly

pupils. Sincency Ipinh/ Itotal

that for any odiffractive zonve zone of theh in the near ical or aspheriche SN6AD1 phe SN60D3.

red lines) and dameter.

iameters that tts. For the sph

mm), and then kllow a similar

ed for the spheADMIOLs of

f the illuminated

gy of the imagand in agreem

e on the other of the near im

of these ADMne of the IOLlens is fully i

image remainc) or add powproves to be n

distance (blue li

the design of herical SN60Dkeeps a constr tendency, berical SN60Daspheric desig

d diameter of th

ges (Fig. 9), iment with theo

hand, the enemage strongly

MIOLs the maxL, which is relilluminated, thns constant (Fer (+4.0D or +

no advantageo

ines) image plan

the ADMIOLD3, as it is ploant value of thut the measur3 IOL. On thegn but differe

he three ADMIO

t is seen that oretical calcul

ergy Itotal of thy decreases fo

ximum apertulatively small,here is no way

Fig. 8) indepen+3.0D) of theous, in terms

nes of the three

L (spherical veotted in Fig. 8he order of ~2red values of e other hand, nt add power

OLs.

for the distanlations only u

he near imageor large pupils

ure involved in, and so is they to send morendently of the

e IOL. In theseof near image

e

ersus aspheric8, the value o20% for largerf Ipinh for large

there were no(SN6AD3 vs

ce image bothup to moderate

e s,

n e e e e e

) f r e o s.

h e


pupil diameters (IOL-pupils of ~3.6 mm for the spherical and ~4.2 mm for the aspheric). In these conditions, which correspond to reduced levels of SA upon the IOL, the maximum energy efficiency achieved is around of the 40% for the spherical and 60% for the aspheric. For larger pupils when the contribution of the refractive part of the IOLs to the distance image is gaining importance, there is a clear reduction of the energy efficiency for both IOLs, in contrast with the theoretically predicted distance dominant behavior of the Acrysof ReSTOR IOLs plotted in Fig. 2. Again, the results obtained with the aspheric ADMIOLs of +4.0D and +3.0 D turn out to be quite similar As for the distance image and large pupils, the significant differences that we have found between the experimental results and the theoretical ones put into question the theoretical distance dominant behavior of the ADMIOLs in the presence of SA. Our results show that most of the additional energy available for the distance image when the EP diameter increases, does not end up in the pinhole image but in the background. This adverse effect is even worse in the case of the spherical multifocal IOL that cannot compensate for properly the SA produced by the model eye.

4. CONCLUSIONS The energy distribution of the distance and near images formed by either spherical or aspheric AMDIOLs or aspheric AMDIOLs of different add power in a model eye, has been characterized as a function of the pupil diameter. Measurements of monofocal spherical and aspheric IOLs put into evidence the influence of the level of SA in the relative energy of the images formed by the IOL. In the case of the ADMIOLs and for the distance image, the results show that with large pupils the level of SA upon the IOLs is too high to correctly focus the available energy on the image. This effect occurs even for the ADMIOLs with aspheric design (SN6AD3 and SN6AD1) and thus, in contrast with the theoretical predictions, there is a strong reduction of the relative energy of the images. In the case of the near image, similar results are obtained with all types of ADMIOLs, which is more likely due to the fact that they share the same design of the diffractive part, and the apertures involved in the near image formation are always small and so is the level of SA upon the IOL.

5. ACKNOWLEGMENTS This research was supported by Spanish Ministerio de Educación y Ciencia and FEDER funds under project DPI2009-08879.

REFERENCES

[1] “WHO | Priority eye diseases. http://www.who.int/blindness/causes/priority/en/index1.html.” [2] M. Larsson, C. Beckman, A. Nyström, S. Hård, and J. Sjöstrand, “Optical properties of diffractive, bifocal,

intraocular lenses,” Appl. Opt. 31, 2377-2384 (1992) [doi:10.1364/AO.31.002377]. [3] A. L. Cohen, “Practical design of a bifocal hologram contact lens or intraocular lens,” Appl. Opt. 31, 3750-3754

(1992) [doi:10.1364/AO.31.003750]. [4] E. M. Vingolo, P. Grenga, L. Iacobelli, and R. Grenga, “Visual acuity and contrast sensitivity: AcrySof ReSTOR

apodized diffractive versus AcrySof SA60AT monofocal intraocular lenses,” Journal of Cataract & Refractive Surgery 33, 1244-1247 (2007) [doi:10.1016/j.jcrs.2007.03.052].

[5] G. Schmidinger, C. Simader, I. Dejacoruhswurm, C. Skorpik, and S. Pieh, “Contrast sensitivity function in eyes with diffractive bifocal intraocular lenses,” Journal of Cataract & Refractive Surgery 31, 2076-2083 (2005) [doi:10.1016/j.jcrs.2005.04.037].

[6] F. Alba-Bueno, F. Vega, and M. S. Millán, “Design of a Test Bench for Intraocular Lens Optical Characterization,” J. Phys.: Conf. Ser. 274, 012105 (2011).

[7] T. Eppig, K. Scholz, and A. Langenbucher, “Assessing the optical performance of multifocal (diffractive) intraocular lenses,” Ophthalmic Physiol Opt 28, 467-474 (2008).

[8] S. Pieh, W. Fiala, A. Malz, and W. Stork, “In Vitro Strehl Ratios with Spherical, Aberration-Free, Average, and Customized Spherical Aberration-Correcting Intraocular Lenses,” Investigative Ophthalmology & Visual Science 50, 1264 -1270 (2009).

[9] S. Pieh, P. Marvan, B. Lackner, G. Hanselmayer, G. Schmidinger, R. Leitgeb, M. Sticker, C. K. Hitzenberger, A. F. Fercher, et al., “Quantitative Performance of Bifocal and Multifocal Intraocular Lenses in a Model Eye: Point Spread Function in Multifocal Intraocular Lenses,” Arch Ophthalmol 120, 23-28 (2002).


[10] T. Terwee, H. Weeber, M. van der Mooren, and P. Piers, “Visualization of the retinal image in an eye model with spherical and aspheric, diffractive, and refractive multifocal intraocular lenses,” J Refract Surg 24, 223-232 (2008).

[11] N. E. de Vries, C. A. B. Webers, R. Montés-Micó, T. Ferrer-Blasco, and R. M. M. A. Nuijts, “Visual outcomes after cataract surgery with implantation of a +3.00 D or +4.00 D aspheric diffractive multifocal intraocular lens: Comparative study,” J Cataract Refract Surg 36, 1316-1322 (2010).

[12] N. E. de Vries, C. A. B. Webers, F. Verbakel, J. de Brabander, T. T. Berendschot, Y. Y. Y. Cheng, M. Doors, and R. M. M. A. Nuijts, “Visual outcome and patient satisfaction after multifocal intraocular lens implantation: aspheric versus spherical design,” J Cataract Refract Surg 36, 1897-1904 (2010),

[13] T. Kohnen, R. Nuijts, P. Levy, E. Haefliger, and J. F. Alfonso, “Visual function after bilateral implantation of apodized diffractive aspheric multifocal intraocular lenses with a +3.0 D addition,” J Cataract Refract Surg 35, 2062-2069 (2009).

[14] G. Munoz, C. Albarrandiego, R. Montesmico, A. Rodriguezgalietero, and J. Alio, “Spherical aberration and contrast sensitivity after cataract surgery with the Tecnis Z9000 intraocular lens,” J Cataract Refract Surg 32, 1320-1327 (2006).

[15] J. A. Davison and M. J. Simpson, “How does the ReSTOR lens work?,” Review of Refractive Surgery, 18-20 (2004).

[16] J. A. Davison and M. J. Simpson, “History and development of the apodized diffractive intraocular lens,” J Cataract Refract Surg 32, 849-858 (2006).

[17] A. Guirao, M. Redondo, and P. Artal, “Optical aberrations of the human cornea as a function of age,” J Opt Soc Am A Opt Image Sci Vis 17, 1697-1702 (2000).

[18] L. Wang, E. Dai, D. D. Koch, and A. Nathoo, “Optical aberrations of the human anterior cornea,” J Cataract Refract Surg 29, 1514-1521 (2003).

[19] J. Schwiegerling, “Intraocular lenses,” in Handbook of optics: Vision and Vision Optics, M. Bass, J. M. Enoch, V. Lakshminarayanan, V. N. Mahajan, and E. V. Stryland, Eds., McGraw Hill Professional, New York (2009).

[20] C. Lee and J. Simpson, “Diffractive multifocal ophthalmic lens,” U.S. Patent No. 5699142 (1997). [21] A. L. Cohen, “Diffractive bifocal lens designs,” Optom Vis Sci 70, 461-468 (1993). [22] N. E. de Vries, L. Franssen, C. A. B. Webers, N. G. Tahzib, Y. Y. Y. Cheng, F. Hendrikse, K. F. Tjia, T. J. T. P.

van den Berg, and R. M. M. A. Nuijts, “Intraocular straylight after implantation of the multifocal AcrySof ReSTOR SA60D3 diffractive intraocular lens,” J Cataract Refract Surg 34, 957-962 (2008).

[23] S. Norrby, P. Piers, C. Campbell, and M. van der Mooren, “Model eyes for evaluation of intraocular lenses,” Appl Opt 46, 6595-6605 (2007).

[24] M. Packer, I. H. Fine, and R. S. Hoffman, “Aspheric intraocular lens selection: the evolution of refractive cataract surgery,” Curr Opin Ophthalmol 19, 1-4 (2008).

[25] International Organization for Standarization, “Ophthalmic Implants, Intraocular lenses Part 2: Optical Properties and Test Methods.”

[26] F. Vega, M. S. Millán, and B. Wells, “Spherical lens versus aspheric artificial cornea for intraocular lens testing,” Opt. Lett. 35, 1539-1541 (2010).

[27] W.K. Pratt, “Digital Image Processing”, 2nd ed., Wiley, New-York, 1991.


Energy balance in apodized diffractive multifocal ...

Documents

Transcript of Energy balance in apodized diffractive multifocal ...