Evaluation of stability and visual quality in Chinese myopic eyes 2 years following FS-LASIK combined with prophylactic corneal crosslinking

To assess corneal stability of femtosecond laser-assisted in situ keratomileusis combined with prophylactic corneal crosslinking (FS-LASIK Xtra) for myopic correction and compare the visual quality to FS-LASIK at 2 years postoperative. Data of 40 patients (80 eyes) receiving FS-LASIK Xtra were collected in the longitudinal study. They were identified as “borderline” with the risk factors including younger in age, thinner corneal thickness, irregular cornea, or weak corneal biomechanics before surgery. 20 patients (40 eyes) of them were recalled for a comprehensive visit at 2 years postoperative, along with a matched group of 27 patients (54 eyes) without risk factors and receiving FS-LASIK alone during the same period. Confounders including age, gender, and baseline refractive parameters were controlled. Refractive status, corneal morphology and biomechanics, epithelial thickness (ET), subjective and objective visual quality, and tear film stability were examined. Generalized linear mixed models were constructed for comparative and correlative analyses. Spherical equivalent (SE), thinnest corneal thickness, integrated radius, central ET changed significantly from 6 months to 2 years after FS-LASIK Xtra (all P < 0.050). There was no statistical difference in SE, biomechanics, higher-order aberrations (HOAs), contrast sensitivity, tear break-up time, and total score of Quality of Vision questionnaire between two surgical groups at 2 years postoperative (all P > 0.050). FS-LASIK Xtra group had greater postoperative objective scattering index (OSI) and corneal densitometry than FS-LASIK group (all P < 0.050). Epithelial remodeling was lower after FS-LASIK Xtra though significance was only observed in pericentral zone (P < 0.050), and its correlation with HOAs was evident in coma (P < 0.050). FS-LASIK Xtra demonstrated its potential in borderline cases for effective myopic correction, along with improvements in corneal morphology and biomechanics during this 2-year visit. However, the additional crosslinking seemed to increase light scatter indicated by higher corneal densitometry and OSI, though patients reported comparable subjective visual outcomes to those of FS-LASIK alone. And postoperative epithelial remodeling still requires long-term monitoring.