Incidence, Indications, and Outcomes of Eyes Needing Early Flap Lifting After LASIK

Surgical and visual outcomes of flap repositioning for various flap-related pathologies post laser in-situ keratomileusis (LASIK)

To evaluate the surgical and visual outcomes of flap repositioning for various post-laser-assisted in-situ keratomileusis (LASIK) flap pathologies. Retrospective review of consecutive cases between April 1, 2017 and February 28, 2022, where surgical flap repositioning was performed following LASIK for various flap-related complications. Of the 6018 eyes, 31 needed flap repositioning (0.51%). Indications were flap displacement and folds in 20 eyes (64%), flap subluxation in five eyes (16%), epithelial ingrowth and interface debris in two each, and one eye each of diffuse lamellar keratitis and incomplete flap. Final best spectacle-corrected visual acuity of ≥ 20/25 was obtained in 25/31 (80%) eyes. The efficacy index pre to post repositioning showed significant improvement (0.86 ± 0.39 vs. 0.63 ± 0.29 preop, P = 0.011). Flap repositioning incidence was significantly higher (7/602 (1.16%)) during the COVID lockdown phases compared to the non-COVID lockdown phase (24/5416 (0.44%, P = 0.019)). The COVID group had lower efficacy (0.72 ± 0.36 vs. 0.90 ± 0.39, P = 0.300) and safety indices (0.85 ± 0.24 vs. 1.06 ± 0.35, P = 0.144) compared to the non-COVID group; however, the results were not statistically significant. The flap displacement rate was statistically higher in nasal hinged (microkeratome) flaps (18/2013, 0.89%) compared to superior hinged (Femto) flaps (13/4005, 0.32%) (0.32%, P = 0.003). Our study shows that flap repositioning has a low incidence in LASIK, with the most common indication being flap displacement/folds. The outcome post flap repositioning was poorer during the lockdown period, perhaps due to the inability to follow up early. Early identification and surgical repositioning are successful in both anatomical and visual restoration.

Late approach for LASIK flap striae

A 24-year-old man was referred for postrefractive surgery evaluation. The patient had a history of uneventful laser in situ keratomileusis (LASIK) in both eyes 3 months previously. According to the surgeon who originally performed the surgery, on slitlamp examination, only microstriae in the left eye was detected on postoperative day 1 and a more conservative follow-up approach was adopted without further immediate intervention. The patient returned only 3 months after surgery, complaining of low vision in the left eye that, according to the patient, had been present since postoperative week 2. The patient was then referred for examination and surgical procedure with a diagnosis of significant postoperative striae. The slitlamp examination revealed a LASIK flap with striae, epithelial filling, and a wrinkled appearance (Figure 1JOURNAL/jcrs/04.03/02158034-202312000-00017/figure1/v/2023-11-20T151558Z/r/image-tiff). There were no signs of infection or inflammation. Originally, the LASIK flap was programmed to be 110 μm. Preoperative manifest refraction in the right eye was -5.25 (20/20) and in the left eye was -5.25 (20/20). Assuming it is a case of late-approach LASIK flap striae, how would you proceed? Would you try to hydrate and lift the flap and just reposition it? Would you avoid lifting and associate phototherapeutic keratectomy (PTK) with excimer laser on top of the flap? Would you consider topo-guided surgery with regularization of the visual axis or even amputation of the flap?

Complications of laser-assisted in situ keratomileusis

Laser-assisted in situ keratomileusis (LASIK) is one of the most commonly performed kerato-refractive surgery globally. Since its introduction in 1990, there has been a constant evolution in its technology to improve the visual outcome. The safety, efficacy, and predictability of LASIK are well known, but complications with this procedure, although rare, are not unknown. Literature review suggests that intraoperative complications include suction loss, free cap, flap tear, buttonhole flap, decentered ablation, central island, interface debris, femtosecond laser-related complications, and others. The postoperative complications include flap striae, flap dislocation, residual refractive error, diffuse lamellar keratitis, microbial keratitis, epithelial ingrowth, refractive regression, corneal ectasia, and others. This review aims to provide a comprehensive knowledge of risk factors, clinical features, and management protocol of all the reported complications of LASIK. This knowledge will help in prevention as well as early identification and timely intervention with the appropriate strategy for achieving optimal visual outcome even in the face of complications.

Incidence, Risk, and Visual Outcomes after Repositioning of Acute Non-Traumatic Flap Dislocations Following Femtosecond-Assisted LASIK

Although the use of femtosecond lasers instead of mechanical devices has decreased the incidence of flap complications following laser-assisted in situ keratomileusis (LASIK), dislocations and striae still occur. Flap repositioning is an effective intervention to improve visual outcomes after acute flap complications in both microkeratome-assisted and femtosecond-assisted LASIK. This retrospective case series included patients undergoing flap repositioning secondary to acute flap dislocation and/or visually significant striae within the first two weeks following femtosecond LASIK (FS-LASIK) from 2015 to 2020 at a single institution. Preoperative, intraoperative, and postoperative de-identified data were analyzed for incidence, risk factors, and visual acuity outcomes. The incidence of flap repositioning was 0.35% in 21,536 eyes (n = 70). Indications for repositioning included acute flap dislocation (35.7%) and visually significant striae (64.3%). High myopia (OR = 3.04, p = 0.001) and patient age over 50 years (OR = 3.69, p = 0.001) were the strongest risk factors for these complications. Prior to flap repositioning, uncorrected distance visual acuity (UDVA) of 20/20 or better and 20/40 or better occurred in 19% and 57% of eyes, respectively. After repositioning, a final UDVA of 20/20 or better and 20/40 or better occurred in 78% and 98% of eyes, respectively. After repositioning, one line of UDVA was lost in two eyes (2.8%) and two lines were lost in one eye (1.4%). Risk factors for acute flap dislocation included high myopia and age over 50 years. Flap repositioning was effective in salvaging visual outcomes.

Comparison of Flap Characteristics Created with Two Different Methods in Laser in Situ Keratomileusis (LASIK)

BACKGROUND

The creation of corneal flap is considered to be the most critical part of laser in situ keratomileusis (LASIK) surgery. Currently, flaps can be created with mechanical micorkeratomes or femtosecond lasers.

OBJECTIVE

To analyze and compare flap characteristics created with two different methods for flap creation in Laser in situ keratomileusis (LASIK).

METHODS

This was a retrospective study. The thickness and morphology of the flap were compared between the two mechanical microkeratomes (group I - Moria M2, group II - Moria SBK One Use Plus) and femtosecond laser (group III - Ziemer Femto LDV). Central flap thickness was measured intraoperatively, while the flap profile was measured with anterior optical coherence tomography at two axes (90° and 180°) and 5 measuring points on the first day, the first week, and one month after the surgery.

RESULTS

Central flap thickness was 110.91±15.79 micrometers (µm) (80-164 µm) in group I, 98.08±13.33 µm (65-136 µm) in group II and 103.52±13.89 µm (66-138 µm) in group III. Anterior optical coherence tomography revealed a meniscus-shaped flap in all three groups at both axes (90° and 180°). The least variability in flap thickness was observed in group III (±6 µm).

CONCLUSION

All three methods of flap creation provide good shape and thickness reproducibility. Ziemer Femto LDV femtosecond laser had the least variable flap thickness in a single flap. Mechanical microkeratomes had slightly lower performance.

15-Month Visual Outcomes and Corneal Power Changes of SMILE in Treating High Myopia With Maximum Myopic Meridian Exceeding 10.00 D

PURPOSE

To evaluate the long-term visual and refractive outcomes, optical quality, and stability of the cornea and axial length after small incision lenticule extraction (SMILE) for the correction of high myopia with a maximum myopic meridian exceeding 10.00 diopters (D).

METHODS

Via a prospective cohort study, 53 eyes (53 patients) with a maximum myopic meridian exceeding 10.00 D were corrected with a VisuMax femtosecond laser (version 3.0; Carl Zeiss Meditec AG, Jena, Germany) at the Zhongshan Ophthalmic Center of Sun Yat-sen University. Refractive outcomes, aberrations, axial length, and corneal curvature were evaluated preoperatively and at 1, 3, and 15 months postoperatively.

RESULTS

At 15 months postoperatively, the efficacy and safety indexes were 0.91 ± 0.25 and 1.15 ± 0.18, respectively. A total of 72% of eyes were within ±0.50 D and 89% were within ±1.00 D of the attempted spherical equivalent, respectively. From 1 to 15 months postoperatively, the significant regression was -0.24 ± 0.28 D (P < .001) on manifest refraction and -0.43 ± 0.54 D (P < .001) on anterior corneal curvature. In addition, a significant increase of 0.20 µm (P = .016) was observed in the spherical aberration. No significant change was observed in posterior corneal curvature (P > .999), including mean keratometry or astigmatism, or in the ocular axis length from 1 to 15 months postoperatively (26.82 ± 0.93 and 26.82 ± 0.95 mm, respectively, P > .99).

CONCLUSIONS

SMILE had long-term safety, efficacy, and predictability when treating high myopia with a maximum myopic meridian exceeding 10.00 D. Both a manifest refraction regression of -0.24 D and a significant spherical aberration increase of 0.20 µm were observed between 1 and 15 months postoperatively, due to the increased anterior corneal curvature. [J Refract Surg. 2019;35(1):31-39.].