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Impact of post cross-linking haze on the repeatability of Pentacam AXL wave: a new hybrid topographer and aberrometer

Poster Details

First Author: S. Arun INDIA

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

Abstract Details


The aim of this study was to analyze the effect of post collagen crosslinking (CXL) haze on the measurement and repeatability of pachymetry(TCT) ,mean keratometry (Km) and corneal aberrations on pentacam AXL wave(Oculus, Wetzlar, Germany).


Narayana Nethralaya, Bangalore


62 eyes of 62 patients with progressive keratoconus who had undergone accelerated Cross linking (ACXL) underwent imaging on pentacam AXL wave 6 months post cross linking.Post-ACXL haze was measured using the densitometry software on the Pentacam AXL wave. Readings of the thinnest corneal thickness (TCT) ,Km and corneal aberrations including higher order aberrations(HOA) from three scans from the device were analyzed. Effect of haze on the repeatability of TCT ,Km and aberrations measurements was evaluated using Within-subject standard deviation (Sw), testï¾–retest repeatability (TRT), and coefficient of variation (COV).


Patients were categorised into Group 1 with haze between 20-40 GSU(54eyes), group 2 with 40-70 GSU(8 eyes). COV Km was 0.7-2.1,TCT was 0.1-3.4,HOA was 20.9-34.4 in group 1, in group 2, COV Km was 1.4-5.7,TCT was 0.2-8.6 & HOA was 18.6-62.2. Repeatability range for Km,TCT & HOA in group 1 was 0.2-0.7 D, 9-12um, +0.31-+0.54, in group 2 was 0.1-0.9D,7-16um,+0.25-+0.72. Corneal densitometry affected repeatability of TCT,km & HOA(P < 0.05)significantly.


Pentacam AXL Wave, a new tool incorporating aberrometry to the existing topographer did show significant change in repeatability post cross linking in patients with varying grades of haze. Hence topography and aberration measurements in the presence of haze should be interpreted with caution. Thus it is important to understand the repeatability range of instruments and understand how it can vary even in post cross linked eyes based on their densitometric haze for better patient understanding.

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