FP1705 :Hybrid Optic New Design Multifocal Intraocular Lens ( IOL ) – Initial Results

Dr. Rushita R Kamdar, R15509, Dr.
Jagadeesh Kumar Reddy K, Dr. Neeraj Shah, Dr.
K S Siddharthan

Abstract:

Purpose: To evaluate distance and near visual outcomes and photic phenomena of a hybrid optic multifocal IOL.

Methods: A prospective, non-randomized clinical case series was performed wherein 40 eyes of 36 patients with senile cataract were implanted with hybrid optic IOL, an IOL with refractive optic for distance and a single, small, central diffractive optic element for near, after phacoemulsification. Visual acuity, Spectacle independence, presence of photic phenomena and patient satisfaction were assessed post-surgery.

Results: 40 eyes had BCVA for distance 20/20 and near vision with distance correction N6. UCVA of 36 patients is 20/30 or better, 4 patients is 20/40. 40 patients had UCVA for near N8 or better and 34 had UCVA for near N6. All the patients were satisfied with their subjective visual quality and only one of them reported  photic phenomena on questioning. 36 patients achieved spectacle independence.

Conclusion: This IOL successfully restores both near and distance vision without any photic phenomenon. It eliminates the visual disturbances associated with diffractive optic design IOL for distance vision.

Introduction

Modern cataract surgery with an intraocular lens (IOL) has the potential to improve a patient’s acuity and refine the refractive error to a given target. But, presbyopic correction sans spectacles still remains the Holy Grail post cataract surgery. By design, monofocal IOLs are limited in range, typically achieving distance, intermediate, or near, but rarely encompassing all distances. The “ideal” IOL would restore the patient’s vision without visual compromises and allow the patient to regain his or her ability to see at all distances.

Since long time, different approaches to IOL design have evolved in an effort to address the impact of presbyopia, and new strategies and technologies will continue to appear. The multifocal IOLs are designed with refractive and/or diffractive optical properties, which focus light on multiple foci and allow the patient to see both near and distant objects.^[1-11] Since the light energy is distributed between more than one image and some energy is lost to useless foci, each primary image produced by a multifocal IOL is thereby fainter and defocused at any given pupil aperture, compared to monofocal or accommodating IOLs that do not split up light in this manner.^[1,2] Diffractive multifocal IOLs provide good levels of distance and near visual acuity independent of pupil diameter, but they are associated with reduced efficiency at intermediate distance and decreased contrast sensitivity for distance and significant dysphotopsia in the form of glare and haloes.^[2]

The fact remains that neither monovision, nor multifocal IOLs nor accommodating IOLs offer a suitable solution.We describe our initial results with a hybrid intraocular lens which provides optimum vision at two focal planes – distance and near both without the occurrence disturbing photic phenomena.

Materials and MethodsL

FORMAT HAS TO BE CORRECTED) Ethics Committee approval was obtained.Informed consentwasobtainedfromallpatientsenrolledbetweenFeb2015tillJan2016.Thestudycohortcomprisedpresbyopicametropicpatientsintheagegroup40-65yearswithcataract.40eyesof36patients were enrolled in this study. TheyunderwentstandardphacoemulsificationwithimplantationofthisHybridIntraocularlens with 3.5 D near addition. Four patients had bilateral implantation of the lens.Patientswereenrolledaftercarefulselectionandscreening.Exclusioncriteriawereahistoryofglaucoma,retinaldetachment,cornealdisease,cornealsurgery,ocularinflammation,neuroophthalmicdisease,maculardegenerationorretinopathy,keratometriccylindergreaterthan1.00diopter(D)andsenilemioticpupils,patientswithtraumaticmydriasisoririscoloboma.Allpatientshadapreoperativeexaminationthatincludedautorefraction, tonometry, uncorrected and corrected distancevisualacuity(UDVA, CDVA),  nearvisualacuity,  biometry(IOLMaster 500,CarlZeissMeditecAG),subjectiveandcycloplegicrefractions,slit-lampevaluationanddilatedfundusevaluation.VisualacuitywasmeasuredatdistanceandnearvisionwithaSnellenvisualacuitychartandconvertedtologMARscores. Axiallength(AL),anteriorchamberdepth (ACD),andkeratometry valuesfromtheIOLMasterwereusedforIOL powercalculation.Alleyesweretargetedforemmetropia.UDVAandCDVA,uncorrectednearvisualacuityanddistance-correctednearvisualacuity(UNVAandCNVA),wereevaluatedat1week, 1month,6monthsand10monthslater.Spectacle independence for the operated eye and patient satisfaction was also analyzed.

Intraocularlens-TheIOLisasinglepiecehydrophobicacrylicfoldable13mmlenswithanopticof6mm.Ithasasymmetricbiconvexdesignwithananteriorasphericprofile.The IOL  has  an  unique design  wherein  its  refractiveopticharboursacentralsmallDiffractiveOpticelement(DOE)segmentof+3.5dioptresadd.Thiswouldtranslatetoanaddof2.57Datthespectacleplane.

Surgical Technique -The surgeries were performed by a singlesurgeon.The pupils were dilated with Tropicamide+PhenylephrineandCyclopentolate.Proparacaine (0.5%) and Lignocainejelly(4%)wasapplied.Lensextractionwasperformedusingastandardphacoemulsificationtechniquethrougha2.8mmincision.Allincisionsweremadeonthesteepestcornealmeridiantoneutralizecornealastigmatism.Afterphacoemulsification,the hybridfoldableIntraocularlenswasinsertedthrough  a  2.8mm  corneal  incision  using  the  injectorinto the capsular bag ensuring adequate centration.Postoperatively,patientswereaskedtoinstillGatifloxacin(0.3%)withLoteprednoletabonate (0.5%)taperedoveramonthalongwithNepafenac(0.03%) for60days.

Results

The mean follow up of these patients was recorded as 12.25 months (8-18 months).The mean patient age was calculated to be 55 years (46-64 years).16 were males and 24 were females. Postoperatively, all patients had a well centred IOL within the capsular bag with a normal Anterior Chamber. Figure 1& 2 depicts post-operative anterior segment photograph of a patient with this IOL.

Figure 1:

Figure 2 :Post dilatation:

All 40eyes(100%) hadBCVAfordistance20/20andnearvisionwithdistancecorrectionN6 which was well maintained till their last follow up.(Figure 3)

UCVA  of  36  eyes (90%)  is  20/30  or  better, and  remaining  4 eyes  patients  is  20/40. (Figure 4)

Mean UCVA for distance is 0.145. Mean BCVA for distance is 0.0 (Figure 5)

Figure 5

40patients(100%)hadUCVAfornearN8orbetterand34 (85%)hadUCVAfornearN6.(Figure 6)

Figure 6

Allthepatientswerehighlysatisfiedwiththeirsubjectivevisualqualityandonlyonereportedanyphoticphenomenaonquestioning (p=0.025).

36patientsachievedspectacleindependence intheoperated eye. All  four  patients  with bilateral implantation  of  this  new design IOL  had  excellent  spectacle  free  vision for both distance  and  near.

Discussion

In our study, eyes with the hybrid lens implantation had a mean UCVA for distance 0.145 and mean BCVA for distance 0.0.In other studies implanted with the ReSTOR IOL, 99.3% achieved 20/40 or better visual acuity. ^[11] (100%)  had  UCVA  for  near  N8  or  better  and  34 (85%)  had  UCVA  for  near  N6. In comparison, binocular uncorrected near visual acuity results demonstrated that 96.7% of the ReSTOR patients achieved 20/40 or better, with 40% having 20/20 or better vision. ^[11]

The excellent visual acuity at two focal planes- distance and near is provided by its novel design.TheIOLisasinglepiecehydrophobicacrylicfoldable13mmlenswithanopticof6mm.Ithasasymmetricbiconvexdesignwithananteriorasphericprofile.ThisrefractiveIOL’sopticharborsacentralsmallDiffractiveOpticelement(DOE)segmentof+3.5dioptersadd.Thiswouldtranslatetoanaddof2.50Datthespectacleplane.Thecentralsegmentfocusesraysfromthenearobjectontotheretina.Thecentralsmallsegmentprovidesincreaseddepthoffocusduetoitspinholesimulatingeffect.Theperipheralareaoftherefractiveopticdirectslighttoadistancefocalpointandisdedicatedtodistancevision.However,duringdistantworktheeffectofthecentralsegmentisnegligibleduetoitssmallsizewhichinturnwouldleadtoasuperimpositionofaninsignificantblurofthenearimageonthedistantimage.^[13] The human brain must adapt to this process of simultaneous imaging.^[14]

Refractive multifocal intraocular lenses are pupil dependent, incorporating different refractive zones to create focal points at varying distances.^[14] DiffractiveIOLs, though pupil dependant,achievemultifocalitybycreationofmultipleringstepsofvariableheightsontheoptic.^[14]Thisdesignhowevercreatesaperceptionofglareorhaloesaroundthedistantimageduetosuperimpositionofnearimageblur.ThedesignofthishybridIOLpotentiallyavoidsthesecompromisestoofferabetterqualityofvision.

Thisnovel lensisdependent onpupilsize, to its advantage.Inastateofambientlightconditionswhentheusualpupilsizewouldbe3.5–4mm,majorityofthelightenergyisfocusedfordistancewithonly 9%focusedfornear.Atnightinastateofpupillarydilatation,thequantaofenergydirectedfordistanceproportionatelyrisesto80%withameagre4%energypassingthroughthecentralDOEpreservinggoodcontrastsensitivityandminimizingtheincidenceofglare,haloes,ghostingofimages.ThisisincontrasttoallDiffractiveMultifocalIOL’swherea significantly large percentageofthelightenergywouldbefocusedforneardistanceresultinginintolerableglareandhaloes.^[1,2] Duringnearwork,thepupilsizereducesresultinginproportionateincreaseintheenergyfocusedthroughthecentralsmallDOE(nearly 40%)resultinginoptimumnearvisualacuity.

Althoughtheoreticallyaperfectlyclearandin-focusretinalimageispresentonlywhenitispreciselyopticallyconjugatewiththeretinaitself,aslightlydefocusedimagewillalsobeinterpretedinthiswaybythebrainaslongasitispositionedwithintheopticalextentofthedepth-of-focus.Aslongasatargetremainswithinthedepth-of-fieldinobjectspace,itsretinalimagewilllikewiseremainwithinthedepth-of-focusinimagespace,andhenceclarityofthetargetwillbeperceived.^[13]SincethisIOLutilizestheprinciplesofrefraction,diffractionandextendeddepthoffocus,itwouldbeapttocallitahybrid  iol.

Weutilizedaself-madequestionnaire,inquiringtheincidenceofglare,haloes,difficultyinnightdriving,satisfactionwithvisualqualityandiftheywouldsuggestthisIOLimplantationtootherpatients.Onlyonepatientcomplainedofdifficultyofdrivingatnight.AllpatientsweresatisfiedwiththisIOLandwerewillingtosuggesttheimplantationofthislenstotheiracquaintancestoo.

Theoretically,feweropticalsideeffectsofthenewIOLshouldbeexpectedbecausetherearenoringsegmentsintheopticforrefractionordiffractionandtheembeddednearsegmentreflectsonlyaminimalquantaofenergy.ThepresenceofonlyasingletransitionzonebetweentherefractiveopticandcentralDOEwilldefinitelyreducethesourceofscatteringandaberrations,minimizeglareandhaloesandimprovecontrastsensitivity.

Though our initial results with the new design IOL have been  extremely gratifying , we need further follow up with a larger sample size. Another limitation would be we did not have a control group to determine whether multifocal IOL implantation is associated with better satisfaction/visual function compared with monofocal IOLs. Also, we focused only on self-reported satisfaction and visual  function. Future studies in our population are needed to

examine the effects of multifocal IOLs on both distance, intermediate  and  near visual acuity and contrast sensitivity.

Conclusion:

This hybrid IOL successfully restores both near and distance vision without any photic phenomenon. It eliminates the visual disturbances associated with diffractive optic design IOL for distance vision. With careful selection of cases and preoperative patient education, the hybrid IOL may become an important tool in the present day cataract surgeon’s armamentatarium. However, long term studies and a large sample size is needed to validate this product conclusively.

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