Femtosecond laser-assisted enhancements after laser in situ keratomileusis

Re-treatment in LASIK: To Flap Lift or Perform Surface Ablation

PURPOSE

To review safety and efficacy outcomes following re-treatment for residual refractive errors in eyes with prior laser in situ keratomileusis (LASIK) and determine the most appropriate course of action for patients.

METHODS

A review of all patients undergoing LASIK enhancement at a single refractive surgery center between 2012 and 2017 was undertaken. Refraction and biomicroscopy results before and after enhancement were collated and analyzed according to the method of enhancement (flap lift or surface ablation).

RESULTS

A total of 108 eyes were included in the analysis; 58 eyes underwent flap lift and 50 underwent surface ablation retreatment with mean times to enhancement of 22.3 and 53.2 months, respectively. The mean spherical equivalent prior to enhancement was -0.43 ± 0.69 and -1.03 ± 1.01 diopters (D) for the flap lift and surface ablation groups, respectively. The absolute difference from intended refraction was statistically significant (lift 0.16 ± 0.24 versus surface ablation 0.31 ± 0.35 D; P = .01). The difference was more pronounced for eyes with prior hyperopia (P = .041). The incidence of haze following re-treatment was 3.4% in the flap lift group versus 10.0% in the surface ablation group, and 8.6% of the flap lift group had evidence of epithelial ingrowth, with 1 eye requiring washout. There was no correlation between time to enhancement, refraction, and incidence of complications following the enhancement procedure.

CONCLUSIONS

There has been a trend toward treating residual LASIK refractive error through surface ablation. This review suggests that flap lift may result in a more accurate refractive outcome, albeit with an expected greater risk of epithelial ingrowth. [J Refract Surg. 2020;36(1):6-11.].

Risk Factors for Epithelial Ingrowth Following Microkeratome-Assisted LASIK

PURPOSE

To analyze the incidence and risk factors associated with epithelial ingrowth following uncomplicated microkeratome-assisted LASIK.

METHODS

All patients who underwent microkeratome-assisted LASIK between January 2006 and December 2014 in a single surgical center were reviewed. Epithelial ingrowth cases were identified and associated factors were assessed.

RESULTS

Overall, 149 (0.49%) of 30,574 cases developed epithelial ingrowth. The epithelial ingrowth group was older compared to controls (35.3 ± 12.3 vs 31.7 ± 10.3 years, P = .001) and had a higher percentage of moderate to high hyperopia (13.7% vs 5.3%, P < .001), early postoperative flap slippage requiring flap repositioning (9.4% versus 2.8%, P < .001), or flap lifting for enhancement (48.6% vs 4.3%, P < .001), were treated with a smaller optic zone (6 mm) (37.7% vs 15.2%, P < .001), with a Moria M2 microkeratome (Moria SA, Antony, France) (70.1% vs 55.5%, P = .02), by low volume surgeons (n < 1,000) (5.8% vs 1.3%, P < .001), in a lower operating room temperature (22.3 ± 1.8 vs 22.8 ± 1.6, P = .005), and with a greater maximum ablation depth (67.3 ± 29.7 vs 57.3 ± 30.3, P < .001). There was a high incidence of epithelial ingrowth in the enhancement group compared to primary LASIK (4.8% vs 0.2%, P < .001). The time between treatments (primary and enhanced LASIK) was significantly greater in the epithelial ingrowth group (mean: 1,110 ± 870 vs 626 ± 662 days, P < .001). There was a significant rise in epithelial ingrowth rates as time between primary and enhancement LASIK increased, peaking at 4 to 5 years (P < .001). In multivariate analysis, flap lifting for enhancement (odds ratio [OR] = 19.5, P < .001), 6-mm optic zone (OR = 2.2, P < .001), moderate to severe hyperopia (OR = 2.4, P = .005), greater ablation depth (OR = 1.005, P < .001), and low volume surgeon (OR = 3.9, P = .01) were associated with epithelial ingrowth (total R² = 15.4).

CONCLUSIONS

The potential risk factors described above may forewarn surgeons as to which individuals merit closer observation for this complication. [J Refract Surg. 2018;34(2):100-105.].

Nd:YAG laser for epithelial ingrowth after laser in situ keratomileusis

PURPOSE

To evaluate the efficacy of neodymium:yttrium-aluminum-garnet (Nd:YAG) laser for treatment of epithelial ingrowth after laser in situ keratomileusis (LASIK).

PATIENTS AND METHODS

Fifty-eight patients with epithelial ingrowth presented to Sohag refractive center, Sohag, Egypt, between January 2015 and March 2017. Only 41 patients (18 females and 23 males, mean age: 33.4 years) involving 41 eyes were indicated for treatment by Nd:YAG laser as the rest of the eyes were only under observation. Patients with epithelial ingrowth were recognized at a mean of 6 months after primary LASIK procedure (range: 2-16 months). Four eyes had undergone previous LASIK enhancements. Four eyes had the epithelial ingrowth removed by flap lift and scrapping. The mean intensity of the spots used was 0.8 mJ with variable number of shots depending on the size and density of the epithelial ingrowth area. Twenty-eight eyes showed complete regression after one session, while the rest necessitated 2-3 sessions for complete resolution. Mean follow-up period was 8 months (range 5-12 months).

RESULTS

Epithelial ingrowth was treated successfully in all 41 eyes. The uncorrected visual acuities were 20/20, and there was no evidence of recurrent epithelial ingrowth after 6 months with no complications reported.

CONCLUSION

YAG laser is a simple, effective outpatient procedure for the management of epithelial ingrowth after LASIK.

Femtosecond-assisted LASIK: Complications and Management

FS-assisted LASIK has become the preferred method for LASIK flap creation due to the precision, accuracy, and reproducibility of the flap creation. Thinner, planar flaps may help prevent cases of post-LASIK ectasia and may have a superior refractive outcome. However, FS flap creation has several unique complications that require early recognition and optimal timely management for the best visual outcomes.

Rescue of primary incomplete microkeratome flap with secondary femtosecond laser flap in LASIK

For laser-assisted in situ keratomileusis (LASIK) retreatments with a previous unsuccessful mechanical microkeratome-assisted surgery, some surgical protocols have been described as feasible, such as relifting of the flap or the creation of a new flap and even the change to a surface ablation procedure (photorefractive keratectomy (PRK)). This case shows the use of femtosecond technology for the creation of a secondary flap to perform LASIK in a cornea with a primary incomplete flap obtained with a mechanical microkeratome. As we were unable to characterize the interface of the first partial lamellar cut, a thick flap was planned and created using a femtosecond laser platform. As the primary cut was very thick in the nasal quadrant, a piece of loose corneal tissue appeared during flap lifting which was fitted in its position and not removed. Despite this condition and considering the regularity of the new femtosecond laser cut, the treatment was uneventful. This case report shows the relevance of a detailed corneal analysis with an advanced imaging technique before performing a secondary flap in a cornea with a primary incomplete flap. The femtosecond laser technology seems to be an excellent tool to manage such cases successfully.

Management of residual refractive error after laser in situ keratomileusis and photorefractive keratectomy

PURPOSE OF REVIEW

To review the various steps and methods in managing residual refractive error after laser in situ keratomileusis and photorefractive keratectomy (PRK).

RECENT FINDINGS

Past studies have shown the efficacy and safety of flap relifts over recuts and for surface ablation over the flap. Other previous and also more recent studies show the use of a femtosecond laser for side cuts only. Recently, the creation of a femtosecond mini flap has been described. New studies also demonstrate the use of collagen cross-linking in postrefractive surgery ectasia.

SUMMARY

Residual refractive error is a known complication after both laser in situ keratomileusis and PRK. A systematic approach should be taken to manage this complication starting with a thorough evaluation to determine if an enhancement is indicated and if so, which method will be the safest and most efficacious for the patient.

Complications of femtosecond laser-assisted re-treatment for residual refractive errors after LASIK

PURPOSE

To report complications of femtosecond laser-assisted re-treatment by the creation of side cuts within the old flaps for residual refractive error after primary LASIK in two patients.

METHODS

Case report.

RESULTS

Three eyes of two patients had complications with a circumferential sliver of stromal tissue displaced during surgery due to overlap of old and new side cuts. The displaced tissue was repositioned and corneal anatomy was restored. Two of three eyes demonstrated improvement in the uncorrected visual acuity, whereas one eye lost two lines of corrected visual acuity due to loss of tissue at side cut resulting from flap manipulation, which was done at 1 week.

CONCLUSIONS

These cases demonstrate a complication of femtosecond laser-enabled side-cut for LASIK enhancement and factors that may lead to this complication and precautions to avoid it.

Creation of a new femtosecond laser-assisted mini-flap to enhance late regression after LASIK

PURPOSE

To describe a method of LASIK enhancement in which a new femtosecond laser-assisted mini-flap is created over the original LASIK flap.

METHODS

The 60-kHz IntraLase femtosecond laser (IntraLase Corp., Irvine, CA) was used to create a new mini-flap over an original LASIK flap for the re-treatment of late regression after LASIK. The diameter of the mini-flap was 7 mm and the attempted flap depth was 100 μm.

RESULTS

The procedure was performed on 10 eyes of 7 patients. No intraoperative or postoperative complications developed in any case during the follow-up. At the 6-month follow-up visit, all eyes were within ±0.5 diopters of the targeted refraction.

CONCLUSIONS

The preliminary results suggest that creation of a femtosecond laser-assisted mini-flap over a previous LASIK flap seems to be a safe and effective procedure for the enhancement of late regression after LASIK. By creating a femtosecond laser-assisted mini-flap that is smaller in diameter than the original flap, the adhesion of the primary flap edges and peripheral interface remain intact, thus decreasing the risk of dislocation of the original LASIK flap and of losing a sliver of tissue.