Clinical Application Of Aspheric Intraocular Lenses

With the development of phacoemulsification, cataract surgeons and patients want to have a better optical quality after cataract surgery. Tecnis Z9001 is an aspheric foldable intraocular lenses(IOLs), designed to provide negative spherical aberration, compensate for positive spherical aberration contributed by the corneal surface to the eye and improve the optical quality. In this study ,we compare the best corrected visual acuity(BCVA), contrast sensitivity and higher-order wavefront aberrations in 44 pseudophakic eyes implanted with two different types of IOLs ,to obtain an objective evaluation of the optical quality of aspheric IOLs.44 eyes of 35 patients were selected randomly from January 2005 to May 2005 to accepted phacoemulsification and implanted IOLs of Canon Staar AQ-310NV and Allergan Tecnis Z9001. Examinations of the BCVA, contrast sensitivity and higher-order wavefront aberrations were carried out at 2 months after cataract surgery.Results: The BCVA of Tecnis Z9001 group was 1. 15 + 0. 19;The BCVA of AQ-310NV group was 1.00 + 0.11 . In the examination of BCVA, contrast sensitivity under the nighttime (at 3. 0c/d, 6.0c/d),nighttime with periglare(at 1.5c/d,3.Oc/d,6. Oc/d), daytime (at 1. 5c/d, 3. Oc/d, 6. Oc/d) and daytime with periglare(at 1. 5c/d, 3. Oc/d, 12. Oc/d) conditions were significantly better in eyes implanted with Tecnis Z9001 than with AQ-31ONV ( P<0. 05 ) . For a 5. 0mm optical zone, the Spherical Aberration, RMS4, RMS5, RMS6 and RMSh in eyes implanted with the Tecnis lens showed significant reduction ( P<0. 05 ). In the examination of Coma, Trefoil and RMS3, there were no significant difference between two group ( P > 0.05 ) .Wavefront science demonstrates that the youthful crystalline lens compensates for aberrations in the cornea. The aging lens loses its balance with the cornea, as both the magnitude and the sign of its spherical aberration change. Older pseudophakic patients have generally the same contrast sensitivity as their age-matched counterparts without cataract. The Tecnis Z9001 IOLs has been designed with a modified prolate anterior surface to compensate for the spherical aberration of the cornea, thus eliminating total ocular spherical aberration. Clinical data demonstrate that this modified prolate IOLs provides superior functional vision, similar to that of younger people, and hence improves visual performance when compared with conventional spherical IOLs. Our clinical data demonstrate: The Tecnis Z9001 IOLs has been designed with a modified prolate anterior surface to provide negative spherical aberration, compensate for positive spherical aberration contributed by the corneal surface to the eye, thus eliminating total ocular spherical aberration and improving the optical quality. Now, With thedevelopment of phacoemulsif ication, the major factor that effect the optical quality of pseudophakic eyes is the higher-order wavefront aberrations. Among the higher-order wavefront aberrations , the spherical aberration is the most important factor.The clinical results confirm the significant reduction of the Spherical Aberration, RMS4 , RMS5 , RMS6 and RMSh in eyes implanted with aspheric IOLs than with spherical IOLs. The optical quality of eyes implanted with aspheric IOLs was significantly better than spherical IOLs.