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Comparison of topographic, keratometric, pachymetric and back difference posterior elevation and D parameters in diagnosing forme fruste keratoconus in the fellow eye of patients with unilateral keratoconus

Session Details

Session Title: Corneal biomechanics

Session Date/Time: Tuesday 08/10/2013 | 08:00-10:30

Paper Time: 08:34

Venue: Elicium 1 (First Floor)

First Author: : O.Muftuoglu TURKEY

Co Author(s): :    V. Hurmeric   F. Orucoglu   O. Ayar        

Abstract Details


To compare the topographic, keratometric, pachymetric, and posterior elevation parameters in diagnosing forme fruste keratoconus (FFKCN) in the fellow eye of patients with unilateral keratoconus


Medipol University Medical School, GATA Faculty of Medicine, Birinci Eye Hospital, Kudret Eye Hospital


80 eyes of 40 patients with unilateral keratoconus in one eye and forme fruste keratoconus in the fellow eye were included and compared with only one eye of 81 control subjects. Each eye was evaluated by Scheimpflug rotating camera imaging (Pentacam, Wetzlar, Germany). Corneal dioptric power in the flattest and steepest meridians, mean corneal power, index of surface variance; index of vertical asymmetry, index of highest asymmetry (IHA), index of highest decentration, central keratoconus index, keratoconus index, central corneal thickness, minimum corneal thickness were recorded. Minimum and maximum progression index and Ambrosio relational thickness values, posterior elevation, the Belin/Ambrosio posterior elevation (BAPE) were evaluated. Receiver-operating-characteristic (ROC) curves were used to determine the overall predictive accuracy of the test parameters.


The means of all parameters were significantly different In three groups (keratoconus, FFKCN, Controls). In ROC analysis, D parameter had the highest area under curve, followed by progression and keratometric parameters, BAPE, posterior elevation, and pachymetry. In FFKCN group, in 42.9% eyes topography and keratometric index were both positive but posterior elevation was negative, followed by 21.4% eyes with only positive topography sign with negative keratometric and negative posterior elevation, 14.3% eyes with negative topography and positive keratometric and positive posterior elevation, 10.7% eyes with all topography, keratometry, and posterior elevation positive, 7.1% eyes all of them were negative, and in 1 eye only posterior elevation was positive. The D parameter was positive (more than 1.50) in 78% of the patients.


D parameter has a good sensitivity and specificity to diagnose FFKCN. Belin Ambrosio posterior elevation seems to be a better parameter than posterior elevation to diagnose FFKCN.

Financial Interest:


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