Abstract
AIM: To assess the visual outcomes and corneal biomechanical properties of myopia patients between laser in situ keratomileusis (LASIK) and LASIK combined with accelerated corneal crosslinking (LASIK Xtra). METHODS: This prospective study analyzed 52 consecutive myopia patients treated with LASIK Xtra and 45 consecutive myopia patients treated with LASIK. Only the right eyes in the two groups were analyzed. The uncorrected distance visual acuity (UDVA), keratometry values, postoperative central corneal thickness (CCT), corneal demarcation line depth, the corneal compensated intraocular pressure (IOPcc), Goldmann-correlated IOP (IOPg), corneal resistance factor (CRF) and corneal hysteresis (CH) from Ocular Response Analyzer (ORA) were analyzed. Further, the correlation between the demarcation line depth and ORA-related biomechanical parameters were analyzed. RESULTS: No significant differences in UDVA, postoperative CCT, or mean K values were found between the 2 groups at 1 to 12mo postoperative follow-up (all P>0.05). The changes of CRF was significantly lower in the LASIK Xtra group compared to the LASIK group (all P<0.05) at all the postoperative visits. The changes of CH were significantly higher in the LASIK Xtra group (all P<0.05). No significant differences were discovered regarding the changes of IOPcc and IOPg posperatively (all P>0.05). Out of 52 cases in the LASIK Xtra group, the demarcation line was present in 40 eyes (77%). The average depth of the demarcation was 220.73±42.70 µm (136 to 288 µm). No significant correlation was observed between the depth of the demarcation line and any of the ORA-related biomechanical parameters such as IOPcc, IOPg, CRF and CH at 12mo (all P>0.05). CONCLUSION: Both procedures demonstrate comparable outcomes in terms of visual acuity, refraction and ablation predictability. This study confirms that corneal biomechanical properties of the included patients weakened after both procedures, but the cornea after LASIK Xtra are stiffer than conventional LASIK.