Free Papers

Ability of maximum keratometry to thinnest pachymetry ratio in detection of early keratoconus with a mean central keratometry lower than 45 diopters

Free Paper Details

First Author: I.Toprak TURKEY

Co Author(s):                        

Abstract Details

Purpose:

To compare diagnostic performance of maximum keratometry (Kmax) to thinnest pachymetry (TP) ratio (Kmax/TP) with Pentacam parameters/indices in diagnosis of early keratoconus (KC) with a mean central keratometry (K) below 45 diopters (D).

Setting:

University-based single-center study

Methods:

This retrospective cross-sectional study included 73 eyes (73 patients) with early KC with a mean central K below 45 D and 70 normal control eyes (70 age-sex matched subjects). Eyes with early KC had corrected distance visual acuity of 20/20, normal biomicroscopy and retinoscopy; whereas typical axial curvature changes with focal corneal elevation and thinning were present on topography. Kmean, Kmax, TP, inferior-superior difference (I-S), Kmax/TP ratio, Belin/Ambrósio Enhanced Ectasia Display (BAD) scores (Df, Db, Dp, Dt, Da and D-final) and maximum Ambrósio Relational Thickness (ARTmax) scores obtained from Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) were used for analysis.

Results:

The early KC group had significantly higher Kmean, K max, I-S, Kmax/TP ratio, BAD-D scores (all); and lower ARTmax and TP compared to those from normal controls. Area under the receiver operating characteristic curve (AUC) and sensitivity-specificity values for the topographical parameters were as follows (from highest to lowest); D-final (AUC=0.998, 97.3%-100%), Da (AUC=0.990, 93.2%-95.7%), ARTmax (AUC=0.990, 94.5%-92.9%), Db (AUC=0.985, 94.5%-92.9%), Dp (AUC=0.984, 94.5%-98.6%), Df (AUC=0.939, 90.4%-80%), Kmax/TP (AUC=0.935, 93.2%-82.9%), TP (AUC=0.918, 86.3%-85.7%), I-S (AUC=0.918, 86.3%-81.4%), Dt (AUC=0.914, 86.3%-84.3) and Kmax (AUC=0.832, 75.3%-77.1%) in discrimination of early KC from normal.

Conclusions:

This study showed that Kmax/TP ratio had satisfying diagnostic ability (also comparable with Df and better than Dt, I-S, Kmax and TP alone) in distinguishing early KC (with a central K below 45D) and might be applied to clinical practice. Furthermore, this parameter does not require complicated algorithms and is not specific for a certain type of a topographer.

Financial Disclosure:

-