Pachymetric Corneal Thinning After Corneal Crosslinking Measured By Scheimpflug And As-Oct And Its Correlation With Corneal Densitometry

To evaluate pre- and postop corneal pachymetry after corneal crosslinking (CXL) in patients with keratoconus (KC) using Scheimpflug and anterior segment OCT (AS-OCT) and correlating with corneal densitometry.

Research Department at Oftalmosalud, Instituto de Ojos, Lima, Peru.

A longitudinal study included keratoconus patients who underwent corneal crosslinking at Oftalmosalud between July 2023 and March 2024. Patients with a minimum follow-up of three months after corneal crosslinking treatment were included, with tomographic evaluation using the Scheimpflug system (Oculus, Pentacam) and AS-OCT (Schwind MS-39). Eyes with post-CXL complications or interfering ocular conditions were excluded. Central corneal thickness (CCT), thinnest corneal pachymetry (TCP), and densitometry were assessed before and three months after CXL. Pachymetric differences between devices (Δ-Devices) were calculated at preoperative assessment ( Δ-Devices PreCXL) and post CXL. (Δ-Devices PostCXL).

A total of 47 eyes from 31 patients were evaluated. The mean CCT measured with Pentacam pre-CXL and post-CXL was 474.9 ± 43.0 µm and 466.5 ± 42.1 µm (p<0.001), respectively, mean CCT measured with AS-OCT was 472.4 ± 43.9 µm pre-CXL and 473.0 ± 45.0 µm post-CXL (p=0.824). The mean TCP measured with Pentacam pre-CXL and post-CXL was 468.4 ± 42.9 µm and 457.6 ± 41.3 µm respectively (p<0.001), mean TCP measured with AS-OCT was 456.1 ± 48.2 µm pre-CXL and 454.8 ± 49.5 µm post-CXL. (p=0.374). A significant positive correlation was observed between the change in corneal densitometry and the delta devices PostCXL.

Pre-CXL and Post-CXL pachymetric measurements obtained via AS-OCT and Scheimpflug imaging  show significant differences. However, these differences are even greater in the postoperative period. Our study shows that these differences are influenced by the increase in corneal densitometric data. Thus, the greater the increase in densitometry, the greater the difference in measurements between devices.