Experimental Study Of Wavefront Aberrations Of Aspherical Intraocular Lens

Objective1.To study the spherical aberrations(SA)of spherical and aspherical intraocularlenses(IOLs)in vitro.2.To assess the effects of aspherical IOLs,including effects on visual acuity,spherical aberration,hith-order aberrations(HOA),coma and trefoil,compared toconventional spherical IOLs.3.Using ZEMAX optical design program to analysis the optical quality of the IOLsin the Hwey-Lan Liou model eye.Methods1.A special optical metric system was set up to measure the wavefront aberrations ofIOLs with a Hartmann-Shack aberrometer.The study was divided into 3 groups:group 1 were CeeOn911A and Tecnis Z9001,group 2 were AR40e and TecnisZA9003,group 3 were AcrySof Natural and AcrySof IQ.IOL aberrations weremeasured continuously under 3mm,4mm,5mm,6mm and 7mm apertures.Thedata was then statistically analyzed.2.Trials were identified by searching for the following electronic database forclinical randomized controlled trials about aspherical IOL,wavefront aberration:Medline,Chinese Medical Current Contents(CMCC),China Nitional KnowledgeInfrastructrue(CNKI).Data were combined for meta-analysis using weighted meandifference (WMD)for discontinous data.3.Using ZEMAX optical design program,(1)analogue monochromatic aberration ofthe IOLs at the length of 550nm,pupil diameters were 3mm～6mm;(2)analoguechromatic aberration of the IOLs at photopic and scotopic conditions,pupildiameters were 3mm and 4.5mm.five lengths at photopic condition were 470,510,555,610 and 650 nm,the weighted were 0.091,0.503,1.000,0.503 and0.107;at scotopic condition five lengths were 420,455,505,550 and 580 nm,theweighted were 0.097,0.513,0.998,0.481 and 0.121.(3)The longitudinalchromatical aberration (LCA)was estimated directly (from the defocus term inthe polynominal expansion of the wavefront aberration). Results1.Spherical IOLs had positive SA,aspherical IOLs had negaitive SA.2.With the increasement of the aperture sizes,the total aberration and the SA of all ofthe IOLs increased accordingly.There were positive correlations between the sizeof aperture and the total and spherical aberrations.(r=0.9257,0.8274,0.7992,p＜0.001)3.15 clinical randomized controlled trials with 436 eyes were included in theaspherical IOL group and 452eyes in the spherical IOL group.The total Z4~0,internalZ4~0,spherical aberration(Z4~0+ Z6~0),hith-order aberration,total aberration,intemalcoma were lower in the aspherical IOL group.The WMD and 95% confidenceinternals(CI)were-0.12,[-0.13,-0.11 ];-0.08,[-0.09,-0.07];-0.17,[-0.19,-0.16],-0.07,[-0.10,-0.04];-0.56,[-0.73,-0.39];-0.06,[-0.10,-0.01] respectively,thedifferences were significant.There were no significant differences in the bestspectacle-corrected visual acuity(BSCVA),total coma,internal horizontal coma,internalvertical coma and total trefoil of the two groups.The WMD and 95% (CI)were0.12,[-0.06,0.29];0.02,[-0.01,0.04];0.02,[ 0.00,0.04];0.02,[ 0.00,0.04];0.00,[-0.04,0.05].4.With the increasement of the aperture sizes,the modulation transfer function (MTF)of the aspherical IOLs decreased,both in the monochromatic and chromaticaberration.5.In the aperture of 3mm～6mm,the MTF of the aspherical IOLs were superior thanthat of the spherical one.6.No matter in the photopic or scotopic condition,the MTF is higher in IOL Hoya(Abbe=43)than IOLSA60AT (Abbe=37).Conclusion1.Aspherical IOLs produced negaitive SA,they are able to compensate for thepositive corneal SA and reduce ocular wavefront aberration,so they can increasethe visual quality.2.With the increasement of the aperture sizes,the total aberration and the sphericalaberration of the spherical and aspherical IOLs increased accordingly,the optical performance decreased.3.After the cataract surgery,the total Z4~0,internal Z4~0,SA,HOA and total aberrationwere significantly decreased in the aspherical IOLs groups than those in thespherical IOLs groups.4.After implantation of the aspherical IOLs,the coma induced by the cornea incisionneed further discussed.5.With the increasement of the aperture sizes,the optical performance of theaspherical IOL decreased.6.The lower the chromatic dispersion of the IOL,the higher the MTF.