Discussion
corneal injury, trauma, adverse injury, postoperative dry eye syndrome, nerve damage, myopia, LASEK, dry eye symptoms, corneal AD
DRY EYE, MYOPIA, HIGH MYOPIA
By taking refractive surgery as a trauma model in our study, this study established that postoperative stress response resulted in postoperative VIP concentration increase, which is highly related to corneal ablation during surgery. Elevated tear VIP after surgery could relieve dry eye symptoms and dry eye symptoms at different stages after surgery are highly correlated with VIP concentration and preoperative basic ocular surface status. The present study can indicate that there is a direct relationship between dry eye and nerve damage after refractive surgery. Under adverse injury stimulation, VIP plays a neuroimmune role in regulating dry eyes, including after refractive surgery.The expression, trophic, and immune roles of VIP present in tears are the focus of this research. VIP is secreted by nerve fibers derived from the parasympathetic nerves, which are distributed mainly in corneal stroma [Before surgery, there was no difference between tear VIP concentration and conditions such as dry eye symptoms, IOP, age, CCT and RCT, as well as VIP concentration between the two groups. This was similar to the results of a previous study [The research found that the increase in tear VIP concentration 1 week after surgery was negatively correlated with corneal AD in both LASEK and FS-LASIK groups: that is, the greater the AD, the lower the increase in VIP concentration. Ablation of the anterior corneal stroma aimed at changing the refraction of myopia could injure the parasympathetic nerves present in it [This study found a significant correlation between VIP concentration and dry eye symptoms, that is, the increase in VIP under stress plays a protective role in relieving dry eye symptoms after corneal injury. This role can be explained by considering the following two aspects: VIP shows an immunoreactive function along the epithelial-stromal junction adjacent to goblet cells, where it stimulates MUC5AC secretion by conjunctival goblet cells [The method used, LASEK or FS-LASIK, has different effects on dry eye symptoms post-surgery. This may be caused by the differences in fabrication of the corneal flap. In LASEK, a corneal flap is created by scraping off part of the corneal epithelium covering the ablation area. This results in disturbance and repair of the corneal environment as well as severe dry eye within 1 week, as confirmed in a rat corneal injury model [Among the factors correlated with dry eyes, subjects who underwent LASEK surgery showed positive correlation with corneal AD, but subjects who underwent FS-LASIK did not. In LASEK surgery, these results mean that the higher the AD, the higher is the possibility of dry eyes post-surgery. The degree of myopia before surgery determines corneal AD, which may explain why patients with high myopia are prone to dry eyes [The positive correlation between postoperative TBUT and preoperative TBUT suggests that preoperative basic ocular surface status determines postoperative dry eye syndrome, which is consistent with the results of previous clinical statistics [COVID-19 delayed follow-up examinations for some subjects, resulting in a reduction in the number of complete samples as well as the inability to observe and study the patients 3, 6 and 12 months post-surgery. Although the current samples were adequate for statistical analysis, further studies with a larger sample size and longer timeframes, such as 3, 6 and 12 months, would validate the accuracy of our results.