Regional changes in corneal shape over a 6-month follow-up after femtosecond-assisted LASIK

Bao, Fangjun; Cao, Si; Wang, Junjie; Wang, Yuan; Huang, Wei; Zhu, Rong; Zheng, Xiang; Huang, Jinhai; Chen, ShiHao; Li, YiYu; Wang, Qinmei; Elsheikh, Ahmed

doi:10.1016/j.jcrs.2018.12.017

Cited by 14 publications

(16 citation statements)

References 30 publications

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“…At first glance, this finding contradicted the further softening trend suggested by IIR and DA; however, because DARatio2mm is defined as the ratio of deformation amplitude between the corneal apex and the location 2 mm away from it, the results in fact indicated that the corneal deformation amplitude 2 mm away from the apex increased more than that at the apex (DA), which in turn showed non-uniform biomechanical changes (softening) across the cornea. The continuous changes in biomechanical parameters over time and asynchronization of these changes in different regions are believed to be related to the wound healing process after surgery, and they may be the cause of the continuous shape changes after surgery reported above and observed by Bao et al (2019) . The corneal curvature changed statistically significant during the follow-up consisted with that, especially in the FS-LASIK group.…”

Section: Discussionmentioning

confidence: 93%

Biomechanical Effects of tPRK, FS-LASIK, and SMILE on the Cornea

Yue

Lopes

Wang

et al. 2022

Front. Bioeng. Biotechnol.

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Purpose: The objective of this study is to evaluate the in vivo corneal biomechanical response to three laser refractive surgeries.Methods: Two hundred and twenty-seven patients who submitted to transepithelial photorefractive keratectomy (tPRK), femtosecond laser-assisted in-situ keratomileusis (FS-LASIK), or small-incision lenticule extraction (SMILE) were included in this study. All cases were examined with the Corvis ST preoperatively (up to 3 months) and postoperatively at 1, 3, and 6 months, and the differences in the main device parameters were assessed. The three groups were matched in age, gender ratio, corneal thickness, refractive error corrections, optical zone diameter, and intraocular pressure. They were also matched in the preoperative biomechanical metrics provided by the Corvis ST including stiffness parameter at first applanation (SP-A1), integrated inverse radius (IIR), deformation amplitude (DA), and deformation amplitude 2 mm away from apex and the apical deformation (DARatio2mm).Results: The results demonstrated a significant decrease post-operation in SP-A1 and significant increases in IIR, DA, and DARatio2mm (p < 0.05), all of which indicated reductions in overall corneal stiffness. Inter-procedure comparisons provided evidence that the smallest overall stiffness reduction was in the tPRK group, followed by the SMILE, and then the FS-LASIK group (p < 0.05). These results remained valid after correction for the change in CCT between pre and 6 months post-operation and for the percentage tissue altered. In all three surgery groups, higher degrees of refractive correction resulted in larger overall stiffness losses based on most of the biomechanical metrics.Conclusion: The corneal biomechanical response to the three surgery procedures varied significantly. With similar corneal thickness loss, the reductions in overall corneal stiffness were the highest in FS-LASIK and the lowest in tPRK.

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Section: Discussionmentioning

confidence: 93%

Biomechanical Effects of tPRK, FS-LASIK, and SMILE on the Cornea

Yue

Lopes

Wang

et al. 2022

Front. Bioeng. Biotechnol.

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“…Although past studies have examined corneal changes post-operatively such as Bao et al, 12 these articles document smaller changes that can occur over time, and do not necessarily delineate how much of that change is actually corneal vs epithelial thickness change. This study attempts to display changes that appear to happen immediately on flap creation that are significant enough that they actually impact the shape of the corneal ablation pattern as the shape of the cornea has significantly been altered from the pre-operatively scanned shape.…”

Section: Discussionmentioning

confidence: 99%

<p>Biomechanical Changes to the Cornea from LASIK Flap Creation Resulting in Inaccurate Ablations and Suboptimal Refractive Outcomes with Topographic-Guided Ablation</p>

Motwani¹

2020

OPTH

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This study documents a biomechanical corneal change related to corneal flap creation in certain patients leading to an irregular ablation pattern and an inaccurate refractive outcome. Methods: This retrospective study included consecutive eyes treated with primary LASIK Contoura using the LYRA Protocol. All LASIK procedures were performed on the WaveLight EX500 excimer laser. Flaps were created with either the Alcon WaveLight FS200 femtosecond laser or the Moria M2 microkeratome. Eyes that were off by greater than or equal to 0.50 diopters (D) sphere or cylinder from the targeted goal within 3 months after surgery were identified. Topographical, higher order aberration, and epithelial maps were created. Of these eyes, approximately 10% of eyes were found to have undergone a biomechanical change upon flap creation that led to an inaccurate outcome. Results: Six representative cases are presented that demonstrate the biomechanical change, outcomes, and treatment. All patients demonstrated an elliptical, irregular ablation pattern on post-operative topography, lateralized the thinnest point of the cornea relative to the corneal apex on Pentacam pachymetry maps, and irregular corneal epithelial thickening at the periphery of the elliptical ablation. Conclusion: A biomechanical change during flap creation can occur in certain types of corneas during LASIK flap creation and subsequent treatment with topographic-guided ablation leading to an irregular ablation and suboptimal refractive outcomes.

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“…All surgeries were performed by the same surgeon. Both groups were treated using standard FS-LASIK procedure, with femtosecond laser (iFS150, Abbott Medical Optics, Inc) to create the flap and excimer laser (Amaris 750, Schwind eye-tech-solutions GmbH & Co. KG) to perform ablation [ 18 ]. In group 1, the procedure was combined with prophylactic CXL.…”

Section: Methodsmentioning

confidence: 99%

“…Only the examinations with instrument-generated quality factor of at least 95% and 90%, for the anterior and posterior surfaces, respectively, were accepted. Original corneal elevation data were exported from the Pentacam and used to calculate the mean regional corneal curvature ( M ) for three subregions of both anterior and posterior surfaces, as described in our previous study [ 18 ]. The three areas were the central region (0–3.0 mm diameter), the paracentral region (3.0–6.0 mm diameter), and the peripheral region (6.0–9.0 mm diameter).…”

Section: Methodsmentioning

confidence: 99%

Laser In Situ Keratomileusis (LASIK) Combined with Prophylactic Corneal Cross-Linking for Correction of Myopia: Regional Analysis of Corneal Morphology

et al. 2022

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Introduction This study evaluated the outcomes of laser in situ keratomileusis (LASIK) combined with prophylactic corneal collagen cross-linking (CXL) in correcting myopia in cases with increased estimated risk of postoperative corneal ectasia, detected by regional analysis of corneal morphology. Methods The retrospective study included 180 eyes of 99 patients. Group 1 (94 eyes of 49 patients) with increased risk of postoperative corneal ectasia, as detected by “Ectasia Risk Factor Score System for LASIK”, underwent femtosecond laser-assisted LASIK (FS-LASIK) combined with prophylactic CXL, using short riboflavin soaking time and low UV energy. Group 2 (86 eyes of 50 patients) with normal corneal topography, who underwent FS-LASIK alone, were used as controls. Refractive and visual outcomes and Scheimpflug topo/tomography were analyzed preoperatively and 1 week, 1 month, and 12 months postoperatively. Mean regional corneal curvature ( M ) values for three subregions (the central 3.0 mm region, the paracentral 3.0–6.0 mm region, and the peripheral 6.0–9.0 mm region) of both anterior and posterior surfaces were calculated. Results An increase in flattening of the peripheral anterior region and more steepening of the posterior paracentral region were shown at 12 months compared to 1 month postoperatively in group 1. The findings were significantly more pronounced than in group 2 ( P < 0.001 and P = 0.035, respectively). The refractive and visual outcomes were comparable in the two groups. Conclusions Prophylactic CXL seems to influence corneal regional reshaping after surgery, while not affecting the 1-year visual and refractive results.

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Regional changes in corneal shape over a 6-month follow-up after femtosecond-assisted LASIK

Cited by 14 publications

References 30 publications

Biomechanical Effects of tPRK, FS-LASIK, and SMILE on the Cornea

Biomechanical Effects of tPRK, FS-LASIK, and SMILE on the Cornea

<p>Biomechanical Changes to the Cornea from LASIK Flap Creation Resulting in Inaccurate Ablations and Suboptimal Refractive Outcomes with Topographic-Guided Ablation</p>

Laser In Situ Keratomileusis (LASIK) Combined with Prophylactic Corneal Cross-Linking for Correction of Myopia: Regional Analysis of Corneal Morphology

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