gms | German Medical Science

Purpose: Corneal astigmatism can be successfully corrected with implantation of a toric intraocular lens (IOL), which has become a standard in modern cataract surgery. The selection of lens power is based on astigmatism measurements taken in the central (about 3 mm) cornea. In this study, we aimed to evaluate how astigmatism in an elderly population changes from the center to the corneal periphery.

Methods: We retrospectively analyzed Pentacam Scheimpflug corneal topography data obtained between October 2004 and June 2019 during routine patient examinations at the Heidelberg University Eye Clinic. The total corneal astigmatism (i.e., from the anterior and posterior surface) was obtained and compared for 3- and 6-mm concentric areas. We included only patients who were 60 years of age or older at the time of examination who had at least 1D of astigmatism. We randomly chose one eye per subject in a total selection of 717 eyes used for statistical analysis.

Results: The mean corneal astigmatism in the center was 1.80 ±0.83D, and at the periphery, it was 1.63 ±0.83D, which was statistically significant (paired t-test, P < .001). However, this difference increased with the cylinder power, as for cases with low astigmatism (<2.5D) it was 0.14 ±0.37D, 0.28 ±0.48D in the range 2.5D to 3.0D, and 0.48 ±0.64D for astigmatism greater than 3.5D. The mean difference in the axis of astigmatism between the 3mm and 6mm zone was 0.1º ± 29.1º (paired t-test, P = .90).

Conclusions: We demonstrated that central corneal astigmatism differs from that measured at the periphery and that a larger difference was found in patients with a higher astigmatism. Our findings suggest that toric IOLs can be improved by decreasing the cylinder power at the IOL's periphery to account for this difference.