Comparison of Corneal Thickness Measurements After Customized Corneal Crosslinking Using High-Resolution Optical Coherence Tomography and Scheimpflug Tomography

Keratometry Changes Between Year One to Seven After Corneal Cross-Linking in Patients With Keratoconus

PURPOSE

We evaluated the timing at and extent to which midterm to long-term keratometric changes can occur in year 1 to 7 after corneal collagen cross-linking (CXL) in patients with keratoconus.

METHODS

We conducted a subgroup analysis of a retrospective cohort study of all consecutive patients who underwent CXL at our cornea center between 2007 and 2011. The inclusion criteria comprised CXL according to the Dresden protocol and a full set of keratometry parameters collected by Scheimpflug tomography preoperatively and at year 1, 3, 5, and 7 after CXL. In addition, best-corrected visual acuity was evaluated.

RESULTS

Sixty-three eyes of 47 patients were enrolled. Mean age was 25.46 years ±7.39 years (80.9% male patients). All relevant keratometric parameters showed significant improvement at year 1 after CXL (except for posterior astigmatism). According to mixed-effects model analysis, they all showed further significant change at different points in time between year 1, 3, 5, and 7 (except for K1). In addition, best-corrected visual acuity improved statistically significant between year 1, 3, 5, and 7. Suspected disease progression was noted in 22.2% of patients, mostly between year 1 and 3 after CXL.

CONCLUSIONS

After initial improvement 1 year after CXL, keratometric and functional parameters were stable until year 5 after CXL in most cases; further improvement can take place even after up to 7 years post-CXL. By contrast, in case of disease progression, changes seem to occur already between year 1 and 3 after CXL.

The Influence of Lens Position, Vault Prediction, and Posterior Cornea on Phakic Posterior Chamber Intraocular Lens Power

BACKGROUND

Achieving precise refractive outcomes in phakic posterior chamber intraocular lens (pIOL) implantation is crucial for patient satisfaction. This study investigates factors affecting pIOL power calculations, focusing on myopic eyes, and evaluates the potential benefits of advanced predictive models.

DESIGN

Retrospective, single-center, algorithm improvement study.

METHODS

Various variations with different effective lens position (ELP) algorithms were analyzed. The algorithms included a fixed constant model, and a multiple linear regression model and were tested with and without incorporation of the posterior corneal curvature (Rcp). Furthermore, the impact of inserting the postoperative vault, the space between the pIOL and the crystalline lens, into the ELP algorithm was examined, and a simple vault prediction model was assessed.

RESULTS

Integrating Rcp and the measured vault into pIOL calculations did not significantly improve accuracy. Transitioning from constant model approaches to ELP concepts based on linear regression models significantly improved pIOL power calculations. Linear regression models outperformed constant models, enhancing refractive outcomes for both ICL and IPCL pIOL platforms.

CONCLUSIONS

This study underscores the utility of implementing ELP concepts based on linear regression models into pIOL power calculation. Linear regression based ELP models offered substantial advantages for achieving desired refractive outcomes, especially in lower to medium power pIOL models. For pIOL power calculations in both pIOL platforms we tested with preoperative measurements from a Scheimpflug device, we found improved results with the LION 1ICL formula and LION 1IPCL formula. Further research is needed to explore the applicability of these findings to a broader range of pIOL designs and measurement devices.