# Corneal densitometry measurements comparison between anterior segment OCT and scheimpflug imaging

## TL;DR

This study compares two devices for measuring corneal density and finds one is more reliable and sensitive to age-related changes.

## Contribution

The study introduces a direct comparison of corneal densitometry repeatability between AS-OCT and Scheimpflug imaging in healthy eyes.

## Key findings

- Casia 2 showed higher repeatability with ICC values over 0.9 and lower CoV compared to Pentacam AXL Wave.
- CD values were positively correlated with age except in zone 1 with Pentacam.
- Measurements from the two devices showed consistent bias and were not interchangeable.

## Abstract

To evaluate and compare the repeatability of corneal densitometry (CD) measurements obtained using both an anterior-segment optical coherence tomography (AS-OCT) device and a Scheimpflug camera system, while also assessing the level of agreement. The study also sought to investigate the correlation of CD with age, gender, and central corneal thickness (CCT) in normal eyes.

CD measurements were obtained using the Casia 2 and the Pentacam AXL Wave. Data were collected on Total Corneal Densitometry and 4 concentric corneal annular areas, these are referred to as zone 1, denoting the central area, through to zone 4, designating the outermost peripheral region. Repeatability was assessed using intra-session test–retest variability, coefficient of variation (CoV), and intraclass correlation coefficient (ICC). The agreement was evaluated using Bland–Altman plots. Correlation analysis was performed between CD, age, gender, and CCT.

The study included 96 healthy volunteers. The Casia 2 demonstrated high repeatability with ICC values exceeding 0.9 in all the corneal zones and lower CoV values compared to the Pentacam AXL Wave (ranging from 1.07% to 2.25% for Casia 2 and from 1.91% to 6.89% for Pentacam).95% LoA were within ± 2 standard deviation from the average mean except from zone 1 (± 2.42).However, the measurements showed a consistent bias among all the corneal zones. CD values were positively correlated with age, except for zone 1 with the Pentacam (p = 0.083).

The findings suggest that the Casia 2 can be a reliable tool for assessing corneal transparency in healthy individuals, however its measurements are not interchangeable with those provided by the Pentacam. The AS-OCT device may be more sensitive in detecting subtle age-related changes in CD within the central zone.

The online version contains supplementary material available at 10.1007/s10792-024-03309-0.