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Diagnostic accuracy of curvature indices in detecting keratoconus

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Session Details

Session Title: Imaging Anterior Segment

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

Paper Time: 15:14

Venue: Room 11

First Author: : M.Roshdy EGYPT

Co Author(s): :    S. Wahba   A. Abodarahim                 

Abstract Details


To investigate the diagnostic accuracy of different curvature indices in early detection of keratoconus (KC); Inferior minus Superior value astride horizontal meridian (I-S h) and astride flattest meridian (I-S f), Index of Height Decentration (IHD), Index of Surface Variance (ISV), Steepest point (Kmax), topographic astigmatism (TA), and skewing of radial axes (SRAX).


Al-Watany Eye Hospital, Cairo, Egypt


In a retrospective study; history taking, clinical examination, and rotating Scheimpflug camera scanning (by Oculyzer II equivalent to Pentacam HR) were done to 128 eyes; 82 normal, 24 forme fruste keratoconus FFKC (apparently normal cornea with the fellow eye with evident keratoconus) and 22 keratoconus (KC). All cases of corneal scars or previous corneal surgeries were excluded. I-S values were calculated manually from 10 points astride the horizontal and flattest meridians. SRAX was calculated from the steepest hemimeridians at 3 mm radius. The other indices are calculated automatically by the device software version 1.17r119.


In differentiating KC (whether evident or FFKC) from normal eyes, the higher area under the receiver operating curve (AUROC) were that of IHD (.840 at cut off value of .011) followed by ISV (.802 at 23), I-S f (.784 at .78), I-S h (.768 at 1.14), Kmax (.650 at 45.3), TA (.638 at 2 D), and SRAX (.562 at 3°). IHD AUROC was statistically greater than those of Kmax, TA, and SRAX (P<.001) but not than those of ISV, I-S f, and I-S h (P= .30, .22, and .09, respectively).


The IHD, ISV, I-S f and I-S h are more accurate in early detection of KC than Kmax, TA and SRAX.

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