Effect of intraocular lens asphericity on vertical coma aberration

PURPOSE: To analyze the effect of asphericity of intraocular lenses (IOLs) on vertical coma aberration after implantation of spherical, spherically neutral, and aspheric IOLs. SETTING: Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom. METHOD: This observational study recruited patients from previous prospective randomized fellow-eye controlled studies comparing aspheric and spherical IOLs (3 spherical, 1 spherically neutral, and 2 aspheric IOLs). At postoperative follow-up visits, maximum pupil dilation was achieved and aberrometry was performed using an iTrace aberrometer with a pupil scan size of 5.0 mm. Data on Zernike coefficients Z(3,-1) (vertical coma), Z(3,+1) (horizontal coma), and Z(4,0) (spherical aberration) and on IOL power were extracted. RESULTS: Two hundred eyes of 100 patients were recruited. Ninety-two eyes had a spherical IOL, 32 eyes had a spherically neutral IOL, and 76 eyes had an aspheric IOL. Vertical coma Z(3,-1) and spherical aberration Z(4,0) values were highest with the spherical IOLs and lowest with the aspheric IOLs (P = .0163 and P<.0001, respectively). There was no difference in horizontal coma aberration between the 3 IOL groups. There was no correlation between IOL power and vertical coma aberration (r(2) = 0.0135, P = .1169). CONCLUSIONS: Conventional spherical IOLs induced more vertical coma than newer aspheric and spherically neutral IOLs. Vertical coma aberration enhances the depth of focus; thus, newer aspheric and spherically neutral designs of IOLs may negatively affect uncorrected near vision.