Comparison of the Optical Image Quality for Presbyopia Correcting IOLs using Modulation Transfer Function TestingW. Maxwell, MD, PhDCalifornia Eye InstituteFresno, CaliforniaFinancial Disclosure: Consultant (Alcon Research, Ltd.)
Testing MethodologyStudy ObjectiveTo compare the image quality of various Presbyopia Correcting IOLs with different designs (accommodative or multifocal; aspheric or spherical) using the modulation transfer function (MTF) testing method and U.S. Air Force 1951 Resolution Target (AFT) testingModulation Transfer Function (MTF) TestingObjective method of measuring image contrast degradation at different spatial frequencies1Modified ISO model eyeThe standard ISO Model Eye1 configuration incorporates a 35 mm doublet lens to converge light to simulate the refractive power of a human cornea The model cornea in the ISO Model Eye is an aberration free lens, and is not representative of a typical human cornea with its inherent positive spherical aberrationThus, a modified ISO model eye simulating the spherical aberration of the internal optics of a young eye was used in this studyRef 1: ISO 11979-2 Ophthalmic implants Intraocular lenses Part 2 Optical properties and test methods, 2000.
Optikos Video MTF measurement system
1024 element detector, a 550 nm narrow band filter, and a 20X microscope objectiveIOLs were mounted in a lens holder under 10 mm of compression, and aligned on the optical axis in a wet cell filled with deionized (DI) water at 35 2 C with the anterior side of the IOL facing the incident light3 and 5 mm apertures used to simulate pupil sizeGreen light illuminates a single slit object located on the front focal plane of a 180 mm collimator The collimated light passes through the model cornea and IOL system that simulates the vergence of a human eyeThe optical bench setupPinhole TargetIOLLight SourceCCD CameraMTF Bench IOL Models Tested (N = 1)IQ ReSTOR SN6AD3 (Aspheric)* ReSTOR SA60D3 (Spherical)*TECNIS ZM900*Acri.LISA 366D*ReZoom NXG1*Crystalens AT-50SE*Crystalens HD500** ReSTOR trademark of Alcon Laboratories, Inc.; ReZOOM & Tecnis trademark of Advanced Medical Optics, Inc.; crystalens trademark of eyeonics, Inc.; Acri.LISA trademark of Carl Zeiss Meditec Inc.
Modulation Transfer Function 5 mm Aperture, Distance FocusSpatial Frequencies of 0 to 100 lp/mm
Modulation Transfer Function 5 mm Aperture, Distance Focus, Discrete frequency of 100 lp/mm (20/20 Equivalent)
Modulation Transfer Function 5 mm Aperture, Distance Focus, Discrete frequency of 50 lp/mm (20/40 Equivalent)
Modulation Transfer Function 3 mm Aperture, Distance FocusSpatial Frequencies of 0 to 100 lp/mm
Modulation Transfer Function 3 mm Aperture, Distance Focus, Discrete frequency of 100 lp/mm (20/20 Equivalent)
U.S. Air Force 1951 Resolution Target Test (AFT)Optikos Optical Testing System The setup for the AFT test was identical to that of the MTF test, except the single slit object was replaced with the AFT An image of the AFT was photographed through each IOL The AFT test includes paired 3-bar target sets used to qualitatively measure resolution efficiency
U.S. Air Force 1951 Resolution Target Test 5 mm Aperture, Distance Focus
ConclusionsThe IQ ReSTOR SN6AD3 aspheric IOL produced the highest overall image quality for MTF and AFT testing with a 5 mm aperture when compared to various presbyopia-correcting IOLs The IQ ReSTOR SN6AD3 aspheric IOL produced the highest image resolution for AFT image testing with 5 mm aperture when compared to various presbyopia-correcting IOLs MTF performance with a smaller aperture (3 mm) was similar among the various IOLs, and slightly higher for IQ ReSTOR SN6AD3 at 100 lp/mmClinical investigation is needed to determine whether superior IOL optical quality demonstrated in optical bench testing results in measurable visual improvements in clinical practice