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Characteristics of corneal front and back in over 600 eyes with keratoconus measured with Scheimpflug tomography

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Session Details

Session Title: Imaging Anterior Segment

Session Date/Time: Monday 07/09/2015 | 14:30-16:30

Paper Time: 16:12

Venue: Room 11

First Author: : M. Shajari GERMANY

Co Author(s): :    M. Remy   W. Mayer   P. Vunnava   J. Buehren   T. Kohnen        

Abstract Details


To better understand corneal changes in eyes with keratoconus compared to eyes of healthy subjects.


Department of Ophthalmology, Goethe-University, Frankfurt, Germany.


Over 1000 eyes in which keratoconus was suspected or already diagnosed were measured with the Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) from April 2010 till January 2015. Only eyes in which index of surface variance (ISV) was above 36 were included in further analysis, as this index was shown to have specifity of over 95% in differentiating normal eyes from eyes with keratoconus. In the remaining 642 eyes amount of corneal astigmatism (CA) and axis (vertical, oblique, horizontal) were analyzed for the front and back surface. Groups were established by age and ISV for further analysis.


CASimK, CATCRP at 3mm, CAfront surface and CAback surface were 3.37 ±1.82 dpt, 3.63 ±1.99 dpt, 3.75 ±2.03 dpt and 0.70 ±0.39 dpt, respectively. Axis of corneal astigmatism was aligned at front and back surface in 98% of eyes when axis was vertical, 59% when axis was oblique and 62% when axis was horizontal. With Increasing age vertical alignment of front and back surface decreased from initially 70.7% (15-25 years, n=116) to 11.5% (55-65 years, n=26) and from 78.4% (15-25 years, n=116) to 30.8% (55-65 years, n=26). Mean vector difference between CATCRP and CASimK was 0.36 at 172°.


Axis alignment between front and back surface is considerably different between healthy eyes and eyes with keratoconus. Whereas vertical alignment on posterior surface predominates independent of front axis alignment in healthy eyes, in eyes with keratoconus posterior alignment matches in most cases anterior alignment. In contrast to normative data, in eyes with keratoconus with increasing age more eyes with oblique and horizontal alignment of axis are seen. Furthermore, vector analysis shows that difference in CASimK to TCRP is considerably higher in eyes with keratoconus compared to difference of healthy subjects.

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