The effects of corneal cross-linking treatment on lens capsule, iris, and other anterior segment parameters in keratoconus patients

Purpose: We aimed to evaluate the changes caused by cross-linking treatment in keratoconus patients by assessing visual acuity, keratometry values, anterior segment parameters evaluated with anterior segment optical coherence tomography (AS-OCT), optical biometry, corneal topography, and specular microscopy before cross-linking (CXL) and at the first month and sixth month after the procedure. Materials and Methods: The study was planned to be conducted on 32 eyes of patients aged 12-40 years, diagnosed with keratoconus, followed up, and with a surgical indication for accelerated CXL at the Ophthalmology Clinic of Yüzüncü Yıl University Faculty of Medicine, Department of Ophthalmology. In the preoperative and postoperative (1st month, 6th month) examinations, the best corrected visual acuity (BCVA) taken with the Snellen chart and converted to logMAR, as well as refraction values, were recorded. Additionally, slit-lamp biomicroscopy and fundus examinations were performed. Images obtained using AS-OCT were transferred to the Image J program, and the anterior chamber angle (ACA 500, ACA 750), angle opening distance (AOD 500, AOD 750), trabecular-iris space area (TISA 500, TISA 750), and iris stromal thickness (IST) values were measured through this program. The central corneal thickness (CCT) and anterior lens capsule complex (ALCC) were manually measured on the device used for the measurement, with the help of a measuring tool. Using optical biometry, axial length (AL), anterior chamber depth (ACD), K1 and K2, and lens thickness (LT) were measured. With corneal topography, the maximum keratometry (Kmax), astigmatic power, central corneal thickness (CCT), and thinnest corneal thickness (TCT) were measured. Endothelial cell density (ECD) was measured using specular microscopy. The values before and after CXL were compared. Results: In our study, 32 eyes of 17 women (53.1%) and 15 men (46.9%) with an average age of 20.78 ± 4.54 years were examined. A statistically significant improvement was found in BCVA (p<0.001), while a statistically significant decrease was observed in CCT-orbscan and TCT at the end of the 6th month (p<0.001). Although the Kmax value at the 1st month was statistically higher than that at the 6th month (p=0.03), there was no significant difference at the 6th month compared to the preoperative value. The K2 (K2-optical) values obtained by optical biometry and the astigmatic power values measured by corneal topography were significantly higher at the end of the 1st month compared to the preoperative values (p=0.003 and p=0.01, respectively), while ECD was found to be lower (p=0.004). However, there was no significant difference between the 6th month results and the preoperative values. The CCT measured by AS-OCT was significantly lower at the end of the 1st month, and the K2 value obtained by autorefractometry (K2-ORM) was significantly higher (p<0.001). There was no statistically significant difference between the preoperative and 6th month results, which were similar. There was no significant difference between the preoperative and 6th month values for ORM spherical/cylindrical value, K1-ORM, AL, and ACD parameters. Similarly, there was no significant change in AOD 500 and 750, TISA 500 and 750, ACA 500 and 750, IST, ALCC, in both nasal and temporal measurements between the preoperative and 6th month values. Conclusion: In our study, accelerated CXL was applied to keratoconus patients, and while an increase in BCVA was obtained, no progression was observed after CXL. This indicates that accelerated CXL is effective in the stabilization of keratoconus, similar to previous studies. The evaluation of parameters such as IST, ALCC, AOD, and TISA, which were not previously examined before and after CXL, is important for our study. However, longer follow-up studies are needed to evaluate these parameters and to observe the effects of Ultraviolet A. Keywords: Keratoconus, cross-linking, anterior chamber angle, anterior segment optical coherence tomography, iris stromal thickness, anterior lens capsule complex