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.