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Pellucid marginal degeneration vs keratoconus: distinction with wide-field SD-OCT corneal sublayer pachymetry

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First Author: N.Luft AUSTRIA

Co Author(s):    D. Krause   M. Shajari   S. Kassumeh   J. Siedlecki   S. Priglinger   W. Mayer     

Abstract Details

Purpose:

To evaluate the capability of spectral-domain optical coherence tomography (SD-OCT) based corneal sublayer pachymetry over a 9.0 mm zone to distinguish between keratoconus and pellucid marginal degeneration (PMD).

Setting:

Department of Ophthalmology, Ludwig-Maximilians-University, Mathildenstraße 8, 80336 Munich, Germany

Methods:

This prospective cross-sectional study included 111 eyes (85 with keratoconus, 26 with PMD) of 100 patients. All patients were examined three subsequent times with the RTVue XR system (Optovue, Inc; Fremont, CA, USA) and pachymetry maps of the total cornea (CT), the epithelium (ET) and the stroma (ST) were generated using the onboard software. Receiver operating characteristic (ROC) analyses and corresponding areas under the curves (AUCs) were computed to elaborate the most valuable pachymetric parameters for distinguishing between PMD and keratoconus. For analysis of reliability, the coefficients of variation (CoV) and intraclass correlation coefficients (ICC) were calculated.

Results:

As compared with keratoconus, PMD exhibited thicker central CT (538±30µm vs. 509±32µm; p<0.01) and ST (480±31µm vs. 454±31µm; p<0.01) as well as thinner ET in the 7-9mm inferior sector (52±4µm vs. 56±5µm; p<0.01). Overall repeatability of (sublayer) pachymetry was comparably good in both keratoconus (ICC ranging between 0.770 and 0.985) and PMD (ICC ranging between 0.652 and 0.993). Measurement reliability in keratoconic eyes was a negative function of Kmax (p<0.01). The best SD-OCT derived parameters for distinguishing between PMD and keratoconus were the calculated indices CI7-9mmdiff (AUC=0.900) and CI7-9mmratio (AUC=0.917).

Conclusions:

Wide-field SD-OCT corneal sublayer pachymetry showed good reliability in PMD and keratoconus and may be useful to differentiate between the two ectatic diseases even in early stages.

Financial Disclosure:

... receives consulting fees, retainer, or contract payments from a competing company, ... travel has been funded, fully or partially, by a competing company