Comparison of anterior segment changes after femtosecond laser LASIK and SMILE using a dual rotating Scheimpflug analyzer

Abstract

Purpose To compare the changes in the anterior segment after femtosecond laser in situ keratomileusis (FS-LASIK) and small incision lenticule extraction (SMILE) using a dual rotating Scheimpflug (DRS) analyzer (Galilei®; Ziemer Ophthalmology, Port, Switzerland). Setting Onnuri smile eye clinic, Seoul, South Korea Design Retrospective Method 218 eyes of 109 patients who underwent FS-LASIK or SMILE for myopic correction were retrospectively studied. Ninety-eight eyes of 49 patients who underwent FS-LASIK were compared to 120 eyes of 60 patients treated with SMILE. A DRS analyzer was used for preoperative and 6-month postoperative anterior segment analyses. Measured variables included the central corneal thickness (CCT), anterior chamber depth (ACD), anterior and posterior keratometry (K), anterior and posterior best-fit sphere radius, and maximum posterior elevation (MPE). Results The estimated lenticule thickness (LT; 87.20 ± 22.87 µm) was significantly thicker in the SMILE group than the ablation depth (69.23 ± 22.24 µm) in the FS-LASIK group. However, there was no significant difference in the CCT decrease using the DRS analyzer. The MPE was significantly increased after both procedures, and there was a statistically significant difference in the change in MPE between the two groups (-1.10 ± 2.12 µm after FS-LASIK; -0.75 ± 2.33 µm after SMILE; p = 0.035). Conclusions The preoperative LT was overestimated using SMILE. Regarding changes in the MPE and posterior K, changes in the posterior corneal surface were greater after FS-LASIK than after SMILE.

Comparison of Predictability in Central Corneal Thickness Reduction After SMILE and FS-LASIK for High Myopia Correction

“…Furthermore, the deviation of difference in CCT reduction in FS-LASIK was slightly larger than that in SMILE (28 lm vs. [10]. In Kim et al's study, the CCT reduction was 20.69 ± 8.73 lm in the SMILE group, which was higher than that in the FS-LASIK group, which was 8.37 ± 7.70 lm [11]. Other studies comparing CCT reduction between these two procedures showed results in agreement with those of Kim et al, i.e., more overestimated CCT reduction was found after SMILE than after FS-LASIK [8,9,12].…”

“…A similar trend of overestimating CCT reduction using the identical excimer laser platform was also reported in previous studies. Supporting evidence has reported that the MEL 80 and MEL 90 excimer laser systems tend to overestimate CCT reduction at 8-31 lm [7,10,11]. Conversely, contradictory results were observed in investigating the consistency on other excimer laser systems, namely, the Allegretto 200 Hz, Visx Star S2, EX500, and Amaris 750S platforms [8,9].…”

“…This highlights significant importance in predicting postoperative RBT with accuracy in high myopia. The comparison of CCT reduction between SMILE and FS-LASIK has been assessed in several previous studies, including in patients with SE more than -9.0 diopters (D) [10][11][12].…”

Reference values of the central corneal thickness with different refractive errors for the adult Egyptian population

“…With late advances, it is possible to measure this value by Pentacam, which maps the whole surface of the cornea [2]. It is an important factor to assess the suitability in refractive surgeries as it is used to exclude patients at risk of postoperative ectasia [3].It is also a measure of the rigidity of the cornea and has an in uence on the precision of intraocular pressure (IOP) estimation by Goldman applanation tonometry (thick corneas offer resistance to it, causing a falsely higher IOP) [4,5].…”