RESUMO
PURPOSE: The human eye exhibits large amounts (2.5 diopters) of longitudinal chromatic aberration (LCA). Its impact on polychromatic image quality, however, has been shown experimentally and by computer modeling to be small or absent. We hypothesized that modest changes in pseudophakic LCA created by higher and lower Abbe number materials will have little or no impact on polychromatic image quality in pseudophakic eyes. MATERIALS AND METHODS: Using published chromatic and monochromatic aberration data from pseudophakic eyes and higher and lower Abbe number materials (37 and 55), we computed monochromatic point spread functions for 21 wavelengths across the visible spectrum. After weighting by either the RGB spectra of a liquid crystal display or by a flat white spectrum, they were weighted by the human spectral sensitivity function (Vλ) before being added to generate polychromatic PSFs. RESULTS: In the absence of monochromatic aberrations, the reduced LCA due to higher Abbe number intraocular lens (IOL) materials resulted in a reduction of 0.08 diopters in the mean defocus generated by LCA. At the retinal plane, the higher Abbe number pseudophakic model produced improvements in polychromatic modulation transfer functions (MTFs) similar to those generated by a 0.05 diopter reduction in spherical defocus. When monochromatic aberrations were added to make the model more representative of actual pseudophakic eyes, the differences in image quality became sub-threshold for human vision or disappeared completely. CONCLUSION: The anticipated gains in polychromatic image quality from employing higher Abbe number IOL materials with reduced LCA do not materialize in plausible aberrated models of pseudophakic eyes.
RESUMO
PURPOSE: To compare mechanical characteristics and stability of Clareon CNA0T0 intraocular lens (IOL) with 4 currently marketed monofocal IOLs and to evaluate axial displacement and simulated dioptric power shift using a range of compression diameters. SETTING: Alcon Laboratories, Inc., Fort Worth, Texas, USA. DESIGN: Experimental study. METHODS: Clareon CNA0T0, AcrySof SN60WF, enVista MX60, Tecnis ZCB00, and Vivinex iSert XY1 IOLs (10 per group) were assessed using standardized methods for axial displacement, optic decentration, and optic tilt per the International Organization for Standardization ISO11979-3. Axial displacement was also measured over a range of compression diameters (9.0 to 11.0 mm). RESULTS: At 10.0 mm compression, the mean axial displacement for the CNA0T0 IOL (0.02 mm ± 0.01 [SD]) was significantly lower than for the MX60, ZCB00, and XY1 IOLs (P < .005). At all compression diameters, the CNA0T0 and SN60WF IOLs had the lowest levels of axial displacement and corresponding simulated dioptric power shift at the corneal plane versus other IOL models. At 10.0 mm compression, the mean optic decentration was within ±0.06 mm for all models, and there were no significant differences between the CNA0T0 IOL and other IOLs. At 10.0 mm compression, the mean optic tilt was no greater than 1.2 degrees for all IOL models evaluated; however, the mean optic tilt for the CNA0T0 IOL was significantly lower than for the MX60 IOL (P < .005). CONCLUSION: The CNA0T0 and SN60WF IOLs showed the lowest levels of axial displacement and corresponding simulated dioptric power shift over all tested compression diameters, indicating they might provide the most consistent refractive outcomes.
