Assessing Corneal Parameters In Keratoconus: Anterion Vs Pentacam

To evaluate the compatibility of corneal curvature and astigmatism and higher-order aberrations (HOAs) measured by: a Scheimpflug camera Pentacam, and a high-resolution swept source optical coherence tomography (SS-OCT) Anterion. This study looks in particular at patients with confirmed or suspected keratoconus. Studies have previously explored these imaging modalities in terms of corneal and anterior segment parameters and results vary on whether there is agreement between the two machines. We wanted to investigate whether the values from both the Pentacam and Anterion were interchangeable between our keratoconus patients and would reduce the need for repeated imaging if we were to begin phasing out use of the Pentacam in clinical practice

Studies have explored the comparative efficacy of anterior segment OCT (AS-OCT) and Scheimpflug imaging in evaluating corneal and anterior chamber measurements. These modalities are used frequently in ophthalmology but use different techniques. The Pentacam employs a 475-nm monochromatic slit of blue light to illuminate the cornea and a 1.45-megapixel camera for photography. The Anterion, a high-resolution SS-OCT, uses a 1300 nm light source with a speed of 50,000 A-scans per second.

A retrospective cross sectional review was undertaken of patients who had undergone both Anterion and Pentacam scanning at the Frimley Park Hospital Eye Treatment centre from the period of November 2024 - February 2025. Scanning equipment was located in the same room for each patient but at variable times in the day and different operating technicians. These patients had values for K1, K2, Kmax, and pachymetry recorded from both machines. Data was collected and analysed using excel and JASP software (JASP Team (2024). JASP (Version 0.19.3)) for statistical analysis.

25 eyes were analysed. Mean differences between the parameters of K1, K2, Kmax, and pachymetry were analysed using intraclass correlation coefficients (ICC), Bland-Altman Plot analyses. Point estimates for ICC were 0.80 (K1), 0.83 (K2), 0.7 (Kmax) and 0.96 (pachymetry). Generally for K1 and Kmax values there was not high correlation with the Anterion and Pentacam with mean differences around 1.64D (K1) and 1.77D (Kmax). Values for K2 correlated slightly less between the two machines, with mean differences around -2.04D. Pachymetry values generally had very good correlation on Bland-Altman measurements - mean difference was -0.64um. P values (paired samples t- test) were 0.006 (k1), 0.002 (K2) , 0.03 (Kmax) and 0.86 (pachymetry). 

Overall there is not a high correlation, especially in the context of keratoconus follow-up and the implementation of using these devices interchangeably in clinical practice needs further investigation. Our results show slightly larger differences in mean values compared to other studies (Bartoleme, 2021) and slightly lower intraclass correlation coefficients (ICC) than other studies (Cheng, 2024) though our study still remained above 0.8 for all values, indicating good reliability. Limitations to the study are the small sample number, lack of demographic information and variation in operator and environment factors. In further studies we would use the same operating technician and perform repeatability analysis with increased sample size.