The present study found a statistically significant but minimal increase in flare value on the post-op 1st day after FS-LASIK; however, no significant difference was found between the pre-op values and the values for the other post-op visits. We only found a negative and weak correlation between the flare elevation on the post-op 1st day and the pre-op flare value.
However, in other studies on anterior chamber inflammation related to other corneal refractive surgeries, such as LASIK performed with MMKs, El Harazi et al. [19] investigated anterior chamber inflammation after LASIK was performed with MMKs and reported high flare values only on the 1st post-op day; they did not find a correlation for this elevation. The values returned to normal on the 7th day post-op. Sen et al. [21] reported that the flare values increased in the first hours after performing the LASIK procedure to correct high astigmatism in patients treated with penetrating keratoplasty before surgery, but decreased to normal levels even on the 1st day. Pisella et al. [20] reported high and prolonged inflammation after LASIK (performed with MMKs); they reported that the increase in the amount of flare was greater on the 1st day post-op, especially in eyes undergoing LASIK; however, they also reported that the flare values returned to normal levels on the 7th day post-op in PRK, but this period was prolonged in LASIK and no significant increase in a flare was observed at any time in patients who underwent intrastromal ring implantations. Pe´rez Santonja et al. [22] reported that, after LASIK with MMKs, there was no increase in the flare values on the 1st, 3rd, and 7th days, post-op. Interestingly, they also reported that the flare values decreased after the 2nd week in comparison to the pre-op value, and they only reached typical values in the 3rd month, post-op.
Our findings suggest that FS-LASIK does not cause a significant increase in inflammation in the anterior chamber, and it does not cause severe damage to the blood-aqueous barrier. The minimally elevated flare values on the 1st day and the near-normal values of consecutive post-op visits may be related to the use of topical steroid drops instilled immediately after surgery and easily controllable mild inflammation. As mentioned above, in the literature, the presence of more pronounced inflammation findings after LASIK performed with MMK in comparison to the values we found with FS-LASIK suggests that MMK is more associated with inflammation than FS-LASIK. To the best of our knowledge, no previous study has investigated anterior chamber inflammation related to FS-LASIK. Our study is the first to report on anterior chamber flare values after FS-LASIK.
We found a statistically significant mean ECD decrease of 4.2% and a modest change in cell morphology at the end of the 3rd post-op month for patients undergoing FS-LASIK. The only significant correlation was between endothelial loss and the pre-op ECD. In contrast, Tomita et al. [23] reported no significant changes in ECD and its morphologies three months after FS-LASIK surgery was performed with two different FS platforms, and no difference was found between the two platforms. In their series of 21 patients comparing FS-assisted LASIK with MMKs, Klingler et al. [24] also reported no significant change in the ECD in both techniques at the end of a 5-year follow-up. In the literature, it has been reported that there is no significant decrease in ECD after PRK [25–26]. Collins et al. [27] reported that they did not detect any change in the endothelium in the 3-year follow-up after LASIK was performed with MMKs. Durrie et al. [28] compared PRK with thin-flap LASIK and reported no significant changes in the ECD at the 3rd post-op month with both techniques and no difference between the two techniques.
The present study found a modest decrease in ECD and a minimal increase in the CV value, thus contradicting the findings reported in the literature mentioned above. However, the reduction in ECD is less than 5%, and it does not have clinical significance in healthy eyes. These findings suggest that endothelial cells may be trying to compensate for the decrease in ECD via polymegatism. Similar to our study, a recently published study by Shaaban et al. [29] reported a statistically significant decrease in ECD and a change in endothelial morphology, although clinically insignificant in both FS-LASIK and small incision lenticule extraction (SMILE). The effect on the endothelial cells may be related to the heat energy generated by the shock waves that occur when the flap is created with the FS laser. This signals that it is important to be careful in cases with endothelial abnormalities, such as endothelial dystrophy because, in the literature, there are case reports of cornea guttata or Fuchs endothelial dystrophy being decompensated after LASIK [30, 31].
This study has some limitations. It only included a small number of cases, it did not include a control or comparison group, and, due to the post-op treatment protocol and ethical reasons because of the risk of diffuse lamellar keratitis and regression, steroid drops were used in all patients. Moreover, the follow-up time was insufficient to enable a more realistic observation of the change in ECD. Furthermore, FS-LASIK is a two-step procedure, and it is difficult to predict from which step the effect originates. A comparison of FS-LASIK with LASIK performed with MMK, or with a procedure performed with only FS, such as SMILE, or a method with no flap, such as PRK, may provide some more helpful information. Nevertheless, in PRK, LASIK, and SMILE, the stromal depth at which the incision and ablation are made are different, which can change their effect. However, the lack of a significant change in the amount of flare reduces the need for a comparison group in order to detect which step is associated with flare change. In addition, since it is well-defined in the literature that LASIK performed with MMK does not significantly reduce the mean ECD, it may be considered that this decrease may be related to the FS laser rather than the excimer laser. The advantages of the present study are that it is a prospective, longitudinal study, and objective measurement methods were used.