Posters

Assessment of the repeatability and agreement of corneal measurements of 4 commonly used topographers in patients post ACXL

Poster Details

First Author: A. Agrawal INDIA

Co Author(s):    N. Pahuja   R. Deshmukh   R. Shetty              

Abstract Details

Purpose:

To assess the repeatability and agreement of corneal measurements using three Scheimpflug-based devices and a slit-scanning imaging device in patients who have undergone accelerated collagen crosslinking (ACXL)

Setting:

Tertiary Eye Care Centre

Methods:

Sixty eyes of 60 patients with keratoconus who had undergone ACXL a year before underwent scans in a random order using the four instruments. Standard methodology was followed to obtain measurements on all devices. A single operator obtained three measurements of each eye from all machines. Thinnest corneal thickness (TCT), steep keratometry (K1), flat keratometry (K2) and astigmatism measurements were obtained. Additionally flat posterior keratometry (PK1) and steep posterior keratometry (PK2) were taken from the Scheimpflug devices. The repeatability of these values were assessed by within-subject standard deviation (Sw), coefficient of repeatability (CRw) and coefficient of variation (CVw).

Results:

The mean TCT was lowest on Orbscan (<0.05). The 95% LoAs were wide for all the parameters with each of the device pairs. For TCT, the Sw and CVw for Orbscan (8.9 and 24.6 respectively) was significantly worse (higher variability) than those of the Scheimpflug devices. The CVw for TCT, K1 and K2 for Orbscan (2.5, 0.8 and 0.7 respectively) was significantly higher than those of Scheimpflug devices.

Conclusions:

Scheimpflug devices are less variable while measuring of corneal parameters in post ACXL eyes when compared to Orbscan and the four devices cannot be used interchangeably for these measurements.

Financial Disclosure:

NONE