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Repeatability of novel hybrid imaging system: pentacam AXL wave with topography and aberrometry in normals vs keratoconus and post cross-linked patients

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First Author: P.Sathe INDIA

Co Author(s):    R. Shetty   G. Kundo   P. Khamar   D. Trivedi   R. Ranade        

Abstract Details

Purpose:

To assess repeatability of Pentacam AXL Wave system (Oculus, Wetzlar, Germany), in measuring flat keratometry (fKm), thinnest corneal thickness (TCT), steep keratometry (sKm), corneal aberrations and total aberrations in normals versus keratoconus(KC) and post cross-linked patients.

Setting:

Narayana Nethralaya Multi-specialty Eye Hospital, Bangalore, Karnataka, India.

Methods:

100 eyes each of normals, keratoconus and post cross-linked patients underwent three consecutive scans on the Pentacam AXL Wave machine, performed by a single operator. Within-subject standard deviation (Sw), test–retest repeatability (TRT), and coefficient of variation (COV) for assessing repeatability and Bland-Altman plots for the agreement between the mean measurements of each machine were examined.

Results:

The COV of steep keratometry was 0.6-1.9, TCT was 0.1-3.4, higher order aberrations (HOA) was 20.5-32.4 in normals as compared to keratoconus where the COV was higher than normals, sKm was 1.2-3.9, TCT was 0.4-4.6 and HOA was 19.6-39.2. Post cross-linked eyes had the highest COV and poorer repeatability with COV for sKm of 1.2-4.6, TCT was 0.3-5.7 and HOA was 18.5-42.3. Thus, in normals, the repeatable range for steep keratometry, TCT and HOA was 0.1-0.5 D, 8-10um, +0.21-+0.51, respectively; in KC eyes, it was 0.2-0.7D, 7-12um, +0.17-+0.61, respectively, and in post cross-linked eyes, it was 0.1-0.8D, 7-15um, +0.2-+0.75, respectively.

Conclusions:

Pentacam AXL Wave, a new tool incorporating aberrometry into the existing topographer, did show repeatable measurements in normals and keratoconus patients. However, its repeatability does alter in post cross-linked eyes significantly. Thus, it is important to understand the repeatability range of instruments and understand how it can vary from normals to keratoconic to post cross-linked eyes for better patient understanding and management. None of the authors have any financial disclosures.

Financial Disclosure:

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