Official ESCRS | European Society of Cataract & Refractive Surgeons
Copenhagen 2016 Registration Programme Exhibitor Information Virtual Exhibition Satellite Meetings Glaucoma Day 2016 Hotel Star Alliance

10 - 14 Sept. 2016, Bella Center, Copenhagen, Denmark

This Meeting has been awarded 27 CME credits


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Evaluation of back elevation and vertical coordinates of pupil center, thinnest location and maximum keratometry in patients with keratoconus

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Session Details

Session Title: Imaging I

Session Date/Time: Monday 12/09/2016 | 14:30-16:30

Paper Time: 14:54

Venue: Hall C2

First Author: : I.Toprak TURKEY

Co Author(s): :    C. Yildirim   V. Yaylali                 

Abstract Details


The aim of the current study is to determine differences in back elevation value, and vertical (y axis) coordinates of pupil center, thinnest location and maximum keratometry (Kmax) between patients with keratoconus and healthy subjects. Moreover, ability of these parameters in discrimination of keratoconic corneas from normals was analyzed.


Private Eye Hospital


This study included 104 eyes of 104 patients with stage 1 and stage 2 keratoconus (keratoconus group) and 87 eyes of 87 age- and sex-matched healthy subjects (control group). The differences in maximum back elevation value (best fit sphere [BFS]), and vertical coordinates (y axis, mm; apex is defined as the origin) of pupil center, thinnest location and Kmax (obtained from Scheimpflug imaging system) were sought between the keratoconus and control groups. Moreover, sensitivity and specificity of each parameter in discriminating keratoconus from normals were determined using a receiver operating characteristic (ROC) analysis and area under the curve (AUC) calculation.


In the keratoconus group, 22 patients had stage 1 and 82 patients had stage 2 keratoconus. Vertical coordinate of the pupil center (+0.15±0.14 vs. -0.01±0.11 mm, p<0.001) and back elevation value (+29.2±13 vs. +14.1±5.6 microns, p<0.001) were significantly higher, while vertical coordinates of the thinnest location (-0.52±0.59 vs. -0.35±0.32 mm, p=0.024) and Kmax (-1.26±1.20 vs. -0.16±1.53 mm, p<0.001) were significantly lower in the keratoconus group when compared to those of the control group. Back elevation (at the level >22 microns with sensitivity-specificity of 65.4%-94.3%, AUC= 0.863, p<0.001) and vertical coordinate of the pupil center (at the level >+0.05 mm with sensitivity-specificity of 70.2%-80.5%, AUC= 0.810, p<0.001) showed good performance in discrimination of eyes with keratoconus from normals.


In eyes with mild to moderate keratoconus, pupil center appears to be located superiorly on the y axis, while corneal thinnest point and Kmax tend to be located inferiorly on the y axis (minus) compared to those of the healthy eyes. Furthermore, keratoconic eyes have higher back elevation value than in the healthy eyes and this parameter seems to have a high ability to detect “true” healthy corneas.

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