Impact of posterior corneal astigmatism on total corneal astigmatism using a new approach of astigmatic analysis

Session Details

Session Title: Pseudophakic IOLs: Toric I

Session Date/Time: Saturday 10/09/2016 | 16:00-18:00

Paper Time: 16:24

Venue: Hall C2

First Author: : D.Piñero Llorens SPAIN

Co Author(s): :    M. Caballero   V. Camps   D. de Fez              

Abstract Details

Purpose:

To evaluate the impact of posterior corneal astigmatism on total corneal astigmatism in healthy eyes using a modified Gaussian approach.

Setting:

Department of Ophthalmology (OFTALMAR). Vithas Medimar International Hospital, Alicante, Spain

Methods:

A total of 92 healthy eyes from 92 patients ranging in age from 21 to 52 years were included in the study. In all cases, a complete corneal analysis was performed with the Scheimpflug imaging system Pentacam (Oculus). With the information obtained, the anterior and posterior corneal power was calculated meridian by meridian (2.5º intervals) assuming that the variation followed a sinusoidal distribution. The total corneal power in each meridian was obtained and the principal meridians were defined as those having the highest and lowest powers. Differences between magnitude and axis of keratometric and our calculated astigmatism was analyzed.

Results:

Mean difference among the magnitude of keratometric and our calculated corneal astigmatism was 0.313 ± 0.241 D (p<0.001), with differences up to 1.5 D. In low astigmatisms, all differences were below 0.5 D. Mean difference among the axis of keratometric and our calculated corneal astigmatism was 5.28 ± 5.36º (p<0.001), with differences up to 28.4º. Differences in axis between the keratometric and calculated method were higher in corneas with oblique astigmatism. Likewise, a significant negative correlation was found between the magnitude of astigmatism and the difference of axis (p<0.001), with the highest difference among the keratometric and calculated axis for 0.5 D of keratometric astigmatism.

Conclusions:

Neglecting the posterior corneal surface astigmatism can lead to an erroneous estimation of total corneal astigmatism, especially in oblique astigmatisms. This may be the cause of refractive surprises when toric intraocular lenses are implanted with a power calculated using only the data of the anterior corneal surface.

Financial Disclosure:

NONE