Correlation of corneal crosslinking-induced change with central corneal thickness and corneal parameters in keratoconus patients

From the files of patients diagnosed with keratoconus who have been followed up in the Hacettepe University Department of Ophthalmology Cornea Unit for the last 10 years, the age and gender were recorded. From the Sirius topography device keratometric (curvature) values of the patients (in 3, 5 and 7 mm rings on the front and back surface of the cornea, the K1, K2, K Avg and Cyl, SimK1 and SimK2, anterior and posterior apex K values), pachymetric values (CCT, TL and AC), curvature asymmetry values (SIf, SIb), elevation-based values (KVf, KVb, rF, rS, Q, RMS, RMS/A), aberration-based values (BCV, BCVf, BCVb) before and after the CXL procedure at 1st, 4th and 6th months were recorded. It was evaluated whether there was a change in these parameters due to cross-linking treatment and how the changes on the front and back surfaces differed. IBM SPSS version 20 (Chicago, IL, USA) program was used in the evaluations and statistical significance was accepted as p<0.05. In our study, it was observed that there was a statistically significant decrease in pachymetric values (CCT, TL and AC) in the 6th month post-op compared to pre-op. Curvature asymmetry values (SIf, SIb) were found to be lower at the 6th month post-op than pre-op on the anterior surface, while no significant difference was detected on the posterior surface. Keratometric (curvature) values K1, K2, K Avg and anterior and posterior apex K values were found to increase in mm (decrease in diopters) on the front surface at the 6th month compared to pre-op, while on the back surface, on the contrary, there was a decrease in mm (increase in diopters) compared to pre-op. It was observed that the SimK1 value was higher in mm in the 6th month postoperatively compared to preop, and the SimK2 value was higher in mm in the 1st month postoperatively compared to preop. It was observed that the KVf anterior surface value was lower in the post-operative 6th month compared to the pre-op, and the KVb posterior surface value was higher in the post-operative 6th month compared to the pre-op. Elevation-based values (rF, RMS, RMS/A) measured on a spherical surface showed that the rF value in mm was higher on the anterior surface and lower on the posterior surface in the 6th month post-op compared to pre-op; RMS and RMS/A values were observed to be lower on the anterior surface and higher on the posterior surface at the 6th month post-op compared to pre-op. Among the elevation-based values (rF, Q, RMS, RMS/A) based on the aspheric surface, it was observed that there was no significant difference in the rF value on the anterior and posterior surfaces at the 6th month post-op compared to the pre-op. It was determined that the Q value was lower on the anterior surface and higher on the posterior surface at the 6th month post-op compared to pre-op. It was observed that RMS and RMS/A values were significantly lower at the 6th month post-op compared to pre-op on the anterior surface, but they did not show a significant difference on the posterior surface. When the elevation-based values (rF, rS, Q, RMS, RMS/A) were examined based on the aspherotoric surface, it was determined that the rF and rS values in mm were higher on the anterior surface and lower on the posterior surface in the 6th month post-op compared to the pre-op. Q, RMS and RMS/A values were found to be lower on the anterior surface and higher on the posterior surface at the 6th month post-op compared to pre-op. It was found that the peripheral Q value was significantly higher on the front surface in the 1st month post-op than in the pre-op, but did not show a significant difference in the 6th month. BCVf value, one of the aberration-based values, was found to be lower on the anterior surface at the 6th month post-op than pre-op. It was determined that BCVb (back surface) and BCV total values did not show a significant difference at the 6th month post-op compared to the pre-op. The results obtained in the study show that although significant results were obtained on the anterior surface after the corneal cross-linking method in keratoconus patients, the disease continues to progress on the posterior surface and the treatment is not effective. Therefore, it may be recommended to examine the reason for these results regarding the posterior surface and to regularly monitor not only the anterior surface but also the posterior surface of patients in clinical practice. Although the time period examined in the study is generally sufficient for an effect to emerge in clinical studies, longer-term observations can be made. However, during this period, treatment measures must be taken to address the progression of the disease on the posterior surface.