Comparison of corneal biomechanical changes after LASIK and F-SMILE with CorVis ST

Abstract

Purpose: To evaluate changes in corneal biomechanics after LASIK and F-SMILE. Setting: Elite Eye Center, Tanta, Egypt. Design: Prospective, randomized, unmasked, interventional comparative case series. Patients and methods: A total of 60 eyes were equally divided into two groups; group A: received LASIK and group B: received F-SMILE. Pentacam and CorVis ST parameters were compared before and 6 months after procedures. P ⩽ 0.05 was used for significance of results. Results: bIOP decreased by 0.762 ± 1.211 mmHg in group A ( p = 0.092), and by 2.52 ± 1.389 mmHg in group B ( p < 0.001) and the difference between groups became significant ( p = 0.001). A1 increased significantly in group A only ( p = 0.036); while A2 decreased insignificantly in both groups. DAR increased significantly in both groups ( p < 0.001, p = 0.022), but the difference between groups remained insignificant ( p = 0.461). IR increased significantly in group A only ( p < 0.001) and the difference between groups became significant ( p = 0.026). ARTH decreased in both groups ( p = 0.245, p = 0.695) and the difference remained insignificant ( p = 0.928). SP-A1 decreased in group A by 8.89 ± 1.38 mmHg/mm ( p = 0.637), and by 32.6 ± 4.39 mmHg/mm in group B ( p < 0.001) and the postoperative difference between groups was significant ( p = 0.013). CBI increased significantly in group A ( p < 0.001), but insignificantly in group B ( p = 0.098) and postoperative difference between groups was highly significant ( p < 0.001). A significant correlation was found between change in CCT and corresponding changes in DAR, IR, and ARTH after surgery in both groups. Conclusion: The significant differences between groups postoperatively as regards bIOP ( p = 0.001), IR ( p = 0.026), SP-A1 ( p = 0.013), and CBI ( p < 0.001) indicate stiffer corneas after F-SMILE and suggest less influence on corneal biomechanics than LASIK.

Short and long term corneal biomechanical analysis after overnight orthokeratology

“…It should be considered that non-contact tonometry is influenced by confounding variables such as corneal thickness [19] . Indeed, significant reductions of bIOP have been reported after the reduction of corneal thickness occurring with different techniques of corneal refractive surgery, such as laser in situ keratomileusis (LASIK) and small incision lenticule extraction (SMILE) [20] . Despite this, the bIOP from the CorVis ® ST device after laser corneal refractive surgery has been found to be in closest agreement with those obtained before surgery compared to other measurements of IOP [21] As shown in Table 2, the same mean value of CCT (547 μm) was found in CG and STOK groups despite some level of thinning was expected in the STOK group considering the mechanism of action of OK. Several factors may account for this apparent contradictory outcome, such as the presence of some level of corneal edema in the OK patients when the measurements were taken in the morning, or the inclusion of thicker corneas in the STOK group with a higher pre-fitting CCT.…”

“…In general, as the CCT decreases below 500 µm, the maximal corneal displacement measured with the CorVis ® ST increases rapidly, being three times larger for CCT below 400 μm [19] . For this reason, significant decreases of AT1 have been reported after laser corneal refractive surgery, especially in those cases in which a more significant reduction of corneal thickness was needed [20,23] . Fernández et al [23] reported that SMILE surgery induced significant changes in the CorVis ® ST parameters of time and deformation amplitude, but these changes were mainly explained by the confounding variable of corneal thickness.…”

Changes in Corneal Biomechanical Properties After Small-Incision Lenticule Extraction and Photorefractive Keratectomy, Using a Noncontact Tonometer

“…20,26 CorVis ST measures corneal deformation through ultrahigh-speed Scheimpflug technology and has been shown to have acceptable repeatability. 12,27,28 Although no gold standard method for measurement of corneal biomechanics is available, the surrogate parameters of stiffness obtained by the CorVis ST arguably provide the closest in vivo assessment of biomechanical properties of the cornea, with numerous studies demonstrating clinically useful applications of the CorVis ST. [3][4][5] Our comparative analysis demonstrated a significant alteration to corneal stiffness after refractive surgery in both groups over a 3-month follow-up. Je ˛dzierowska et al 23 reported that the most important biomechanical parameters in clinical practice are those related to the deformation amplitude (DA ratio) and stiffness parameters (SP-A1 and SP-HC), especially in the early postoperative period after refractive surgery.…”

A comparative and prospective study of corneal biomechanics after SMILE and FS-LASIK performed on the contralateral eyes of high myopia patients

“…Spiru et al reported that the SMILE procedure resulted in a better corneal stress resistance than FS-LASIK in an ex vivo study (4). SMILE had less influence on corneal biomechanics than did LASIK in vivo (5,6), whereas other studies suggested that no significant differences were found in corneal biomechanics between the two groups in vivo (7,8). Moreover, none of these studies focused on patients with high myopia (6)(7)(8).…”