Experimental evaluation of online optical coherence pachymetry for corneal refractive surgery

Abstract

In this experimental evaluation, online OCP revealed to be a precise and reproducible method to assess the central corneal thickness and its changes intraoperatively. This could be important to monitor incisional and excimer laser-based corneal refractive procedures, such as PRK or LASIK.

Online optical coherence pachymetry to evaluate intraoperative ablation parameters in LASIK

“…As reported previously [27][28][29]31], online OCP was reliable, easy to perform, and did not affect the LASIK procedure. Online OCP provided intraoperative noncontact and continuous measurements of the changes of the central corneal thickness and several ablation parameters during LASIK.…”

“…The correlation coefficient gave a measure of the linear ablation rate, in terms of depth ablated over time, with values similar to previous experimental bovine studies [11,12]. Although, in this clinical study, a high pulse-to-pulse stability was noted, compared to polymethylmethacrylate (PMMA) ablation studies in corneal tissue, a greater measurement error must be considered [11,12,28], and the measured ablation values were higher than calculated. Also, with intraoperative contact ultrasound [8,13,21,22] and optically [4,26,29,31], significantly more tissue was ablated intraoperatively than predicted.…”

“…The results of our clinical study with online OCP confirmed that corneal stromal dehydration during laser ablation was mainly responsible for the differences observed between the calculated and intraoperatively measured values. Thus, intraoperative online OCP could, further, be useful to investigate the in-vivo effect of evaporation on corneal hydration, corneal water content, and tissue composition, as well as excimer-laser-tissue interactions in LASIK [28]. This was the first study to correlate intraoperative ablation parameters with the postoperative refraction outcome after LASIK.…”

“…The technical details of this system have been described previously [27][28][29]31]. The most important features of online OCP for this study allowed continuous measurement of the central cornea during the LASIK procedure and the ablation phase in realtime without disturbing the procedure itself [29,31].…”

“…Recently, we presented a high-resolution and noncontact intraoperative monitoring of the central corneal thickness changes by integrating optical coherence pachymetry (OCP) into an excimer laser in experimental [28] and clinical studies [27,29,31]. These studies revealed that online OCP allowed continuous measurement of the intraoperative corneal changes, such as the flap and the residual stromal thickness, with a high reproducibility.…”