Improving the reliability and repeatability of corneal curvature assessment through image analysis of topographic maps and the compensation of torsion

Session Details

Session Title: Cornea Surgical II

Session Date/Time: Tuesday 16/09/2014 | 08:00-10:30

Paper Time: 08:00

Venue: Boulevard B

First Author: : P.Buckhurst UK

Co Author(s): :    C. Hamer   H. Buckhurst   C. Purslow   N. Habib     

Abstract Details

Purpose:

To determine if compensating for eye torsion can improve the reproducibility of identifying the location of the steepest corneal meridian. In addition the study examined how the image analysis of topographic maps could further aid in the identification of the steepest corneal meridian.

Setting:

Plymouth University, Peninsular Allied Health Centre, UK

Methods:

Thirty-five subjects with corneal astigmatism greater than 1.25D were assessed using Scheimpflug imaging (Pentacam HR) on two separate visits. The orientation of the steepest corneal meridian was determined using three methods: utilizing the conventional simulated keratometry (SimK) readings and via image analysis of both axial and tangential corneal curvature topographical maps. In addition eye torsion was compensated for using image analysis of iris features to determine if this rotation adversely affected the repeatability of the identification of the steepest corneal meridian

Results:

The average difference of the orientation of the steepest corneal meridian, determined via SimK, between two visits was 4.00±3.96°. There was a significant improvement in the repeatability (p=0.039) when eye torsion was compensated for through image analysis (3.03±2.67°). Image analysis of the axial topography maps did not enhance the repeatability of the measurements; however, applying this method to the tangential maps proved to provide a more repeatable determination of orientation in comparison with the SimK value (p=0.020).

Conclusions:

Determination of the orientation of the corneal principal meridians can be made more reproducible if eye torsion is accounted for through image analysis of iris features and by studying the tangential topography maps. This may allow more precise identification of corneal principal meridians in situations where this may be critical such as in the use of toric IOLs and should therefore be considered alongside the basic measurement of SimK axis.

Financial Interest:

NONE