Traumatic displacement of laser in situ keratomileusis flaps: an integrated clinical case presentation

Flap-making patterns and corneal characteristics influence opaque bubble layer occurrence in femtosecond laser-assisted laser in situ keratomileusis

Background

Opaque bubble layer (OBL), which generates from photo-disruptive procedures on the cornea, has been a common phenomenon during femtosecond laser-assisted refractive surgeries and it would potentially impact eye tracking and flap lifting. And we have observed that an updated flap-making pattern could form less OBL clinically than the traditional pattern, which needed further approval. Thus, the purpose of this study is to prove our observation and investigate the possible risk factors related to the occurrence and type of OBL in laser in situ keratomileusis (LASIK) flaps using the Visumax laser system.

Methods

This prospective study included 167 eyes of 86 patients (mean age: 27.5 ± 6.1 years) undergoing bilateral femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) for myopia/myopic astigmatism by the same surgeon from April 2020 to August 2020. Preoperative data on refraction, central corneal thickness (CCT), and keratometry as well as intraoperative data were included for analysis. A new flap-making pattern creating an offset between flap-cut and side-cut was adopted to compare with the traditional pattern. The operation video of flap formation was analyzed to identify the existence and type of OBL. The area covered by OBL and the ratio of OBL to flap were calculated using Image J software.

Results

Among 167 eyes, 54 eyes (32.3%) developed OBLs, consisting of 31 as hard OBL coexisting with soft OBL, and 23 as soft OBL alone. The OBL incidence was significantly reduced in eyes with the new flap-making pattern compared with the traditional pattern (13.8% vs. 52.5%, P < 0.001). Hard OBLs had larger area ratios than soft OBLs (14.3 ± 8.3% vs. 1.1 ± 1.8%, P < 0.001). Univariate analyses revealed that eyes with more myopia, thicker CCT, and traditional flap-making patterns were more likely to develop OBLs. Multivariate analysis further confirmed that more myopia, thicker CCT, and traditional flap-making pattern were risk factors for OBLs. A Larger corneal diameter was associated with a higher incidence of hard OBL when applying the traditional flap-making process.

Conclusion

More myopia, thicker CCT, and larger corneal diameter were risk factors for OBL development during flap creation, whereas a flap-making pattern with an offset between flap-cut and side-cut could reduce the incidence of OBL.

Efficacy and Safety of Surgically Managed Late Traumatic LASIK Flap Displacements in a Study of 66 Cases

PURPOSE

To evaluate safety and efficacy in the management of flap displacement after laser in situ keratomileusis (LASIK) and subsequent complications.

METHODS

This was a retrospective study performed using data recorded at the center's database from October 2002 to August 2021. Efficacy and safety were both converted to binary outcomes (loss of one or more lines and no change or gain in lines of visual acuity). The effects of time from surgery to complication and from complication to repair were assessed and the odds ratios and probabilities were calculated. The same procedure was applied to investigate the effect of these temporal variables on complications.

RESULTS

A total of 66 eyes with late traumatic LASIK flap displacements were studied. Efficacy remained unchanged in 48 patients (64 eyes, 75%), and safety remained unchanged in 53 patients (59 eyes, 90%). Sixty-six patients (64 eyes, 100%) achieved visual acuity values of 20/40 and 45 patients (64 eyes, 70.3%) achieved values of 20/20. The flap displacement was resolved in the first 24 hours (SD ± 0.1 days). Surgery was performed in 58 patients (65 eyes, 90%). Epithelial ingrowth was the most frequent complication. Patients who underwent surgery tended not to lose lines (P = .05). The risk of developing epithelial ingrowth increases with time after LASIK surgery until traumatic flap displacement (odds ratio: 1.001; P < .001). The prevalence of dislocation during the study period was 0.012%.

CONCLUSIONS

Visual safety values were favorable after resolution of the flap complication. Immediate surgical management leads to better visual efficacy, and the time between LASIK and trauma increases the risk of epithelial ingrowth after flap displacement. [J Refract Surg. 2022;38(4):270-276.].