Posters

Comparison of corneal tomography with OCT or Scheimpflug imaging

Poster Details

First Author: A.Ivarsen DENMARK

Co Author(s):    J. Hjortdal                    

Abstract Details

Purpose:

To compare main tomographic data obtained using Scheimpflug or OCT imaging in normal and keratoconus eyes.

Setting:

University eye clinic

Methods:

One eye of 44 patients examined for keratorefractive surgery and 34 patients with known keratoconus (grade 1-4) were measured with Pentacam HR (Oculus, Germany) and Casia 2 (Tomey, Japan). Tomographic data including front- and back-surface radius of curvature (Rf and Rb), maximum front surface keratometry (Kmax), minimal corneal thickness (CCT), and cornea front- and back-surface coefficient of asphericity (Qf and Qb) were compared using regression analysis, Bland-Altman analysis, and intraclass correlation (ICC 2,1).

Results:

In both refractive myopic patients and keratonus patients, Casia 2 and Pentacam showed high correlation (r2 more than 0.90) and high ICC (ICC more than 0.86) between Rf and Rb, Kmax, and CCT. Bland-Altman plots showed no proportional bias between the two methods, except for Kmax, where the difference between the methods was significantly correlated with the average measurement (r2 = 0.60; p = 0.001). For Qf and Qb the two methods showed poorer correlation (r2 = 0.45 to 0.68) and poorer ICC (ICC = 0.49 to 0.75)

Conclusions:

Pentacam HR and Casia 2 show high correlation between average Rf, Rb, and CCT, with differences of little clinical significance and no proportional bias. In contrast, Kmax shows significant proportional bias with Pentacam measuring higher values than Casia 2, and an increasing difference with higher Kmax. For corneal asphericity, the two methods show only moderate correlation and ICC. Overall, the two methods show very good agreement with respect to overall corneal shape and thickness. However, more specific shape related measurements including Kmax, Qf and Qb show poorer compliance, why the two methods cannot be used interchangeably.

Financial Disclosure:

None