A biomechanical and tomographical analysis of the “healthy” partner eye in unilateral keratoconus.

Abstract

Purpose : The keratoconus is a progressive corneal ectasia with an incidence of ca. 1/2000 in the European population. Typically at the early diagnosis the keratoconus affects both eyes with an asymmetrical severity. The purpose of this study is to point to the biomechanical changes of the topo- and tomographically “healthy” partner eye in the so-called “unilateral keratoconus”.

Methods : In this retrospective study, we reviewed the clinical records of 20 out of the 1280 patients of our Homburg Keratoconus Center (HKC), with so-called “unilateral keratoconus” and analyzed the topo- and tomographical results of the OCULUS Pentacam HR as well as the biomechanical corneal properties using the Ocular Response Analyser (ORA) (Keratoconus Match Index (KMI)) and Oculus Corvis ST (Tomographic Biomechanical Index (TBI)). Cut-off values for typical keratoconus are defined as < 0.72 for KMI and > 0.29 for TBI. We used a healthy control group of 20 colleagues to compare the results.

Results : Compared to the control group (0.97 ± 0.26, min: 0.14 max: 1.52), the so-called healthy partner eye (0.70 ±0.31, min: 0.14 max: 1.22) showed a significantly (p-value = 0.01) more pathological KMI. 9 of 20 partner eyes (45.0 %) had a KMI < 0.72 and were pathological. Compared to the control group (0.09 ± 0.12, min: 0.0 max: 0.39) the TBI of the so-called healthy partner eye (0.18 ±0.26, min: 0.0 max: 0.99) did not differ significantly overall (p-value = 0.19). However, 3 of the 20 eyes (15.8 %) had a TBI > 0.29 and were considered pathological.

Conclusions : Topo- and tomographically unilateral keratoconus shows frequently biomechanical changes on the primarily considered “healthy” partner eye. This should be considered before planning any type of refractive corneal surgery.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Keratoconus Match Index (KMI)

 

Tomographic Biomechanical Index (TBI)