Creation of an extremely thin flap using IntraLase femtosecond laser

Corneal scarring from laser in situ keratomileusis after epikeratoplasty: clinical and histopathologic analysis

A 47-year-old woman required penetrating keratoplasty in the right eye after developing delayed visually significant corneal scarring bilaterally after laser in situ keratomileusis (LASIK) in 1997 following epikeratoplasty in 1987. Spectral domain ocular coherence tomography of the left cornea showed a 100 μm lenticule with a LASIK flap posterior to the host Bowman layer at 250 μm. Histopathology and electron microscopy of the right corneal button showed a 120 μm lenticule with a LASIK flap within the lenticule at 100 μm. Clinically significant scarring was present within the LASIK flap interface, within the lenticule stroma, and within the area of the underlying host Bowman layer. There were keratocytes at the junction between the LASIK flap and lenticule stromal bed. Although epikeratoplasty is no longer practiced, post-epikeratoplasty patients may present for refractive surgical options and LASIK carries significant risks for corneal scarring in these individuals, especially when using flap-creating devices that may create thin LASIK flaps.

Factors influencing corneal flap thickness in laser in situ keratomileusis with a femtosecond laser

Purpose

To evaluate factors responsible for the variability between intended and achieved corneal-flap thickness during femtosecond laser-assisted laser in situ keratomileusis (LASIK).

Methods

A prospective, nonrandomized, case study was performed on 35 eyes of 18 consecutive patients who underwent LASIK surgery using the 60 kHz femtosecond laser microkeratome. Eyes were assigned to three different thickness groups, with 110-, 120-, or 130-µm cut depths. Anterior segment optical coherence tomography was used to assess the morphology of 35 LASIK flaps at postoperative one week postoperatively. The flap thickness was assessed at seven measuring points across each flap. Patient age, preoperative spherical equivalent, manual keratometry, preoperative central pachymetry, and regional variability of the cornea were evaluated to determine where they influenced the achieved corneal flap thickness.

Results

Cuttings of all flaps were easily performed without any intraoperative complications. Flap-thickness measurements had a mean of 115.21 ± 4.98 µm (intended thickness, 110 µm), 121.90 ± 5.79 µm (intended, 120 µm), and 134.38 ± 5.04 µm (intended, 130 µm), respectively. There was no significant difference between the 110-µm and 120-µm groups when compared with the 130-µm group (one-way analysis of variance test, p > 0.05). Patients' age, preoperative spherical equivalent, manual keratometry, and preoperative central pachymetry did not affect the achieved flap thickness (Pearson correlations test, p > 0.05). The reproducibility of flap thickness in the central 1.5-mm radius area was more accurate than that in the peripheral 3.0 to 4.0-mm radius area (paired samples t-test, p < 0.05).

Conclusions

Femtosecond laser-assisted LASIK is likely to reproduce a reliable thickness of the corneal flap, which is independent of corneal shape factors or refractive status. Future studies should focus on variations in corneal biomechanical factors, which may also play an important role in determining flap thickness.

Comparison between femtosecond laser-assisted sub-Bowman keratomileusis vs laser subepithelial keratectomy to correct myopia

PURPOSE

To compare femtosecond laser sub-Bowman keratomileusis (FSBK) vs laser subepithelial keratectomy (LASEK) to correct myopia.

DESIGN

Retrospective, nonrandomized, interventional, comparative case series.

METHODS

Two thousand one hundred and eight eyes were included in the study. We compared 1,072 eyes treated with FSBK vs 1,036 eyes treated with LASEK with or without mitomycin C (MMC). Visual and refractive results were evaluated 1 day, 1 week, and 1 and 3 months postoperatively.

RESULTS

Preoperative mean sphere and best spectacle-corrected visual acuity (BSCVA) were -3.93 diopters (D) vs -3.87 D (P = .5) and 1.12 vs 1.12 (P = .8) in FSBK and LASEK, respectively. Uncorrected visual acuity (UCVA) was 0.92 vs 0.62, 0.98 vs 0.78, 0.96 vs 0.91, and 1.06 vs 1.03 in FSBK and LASEK, respectively, at 1 day, 1 week, and 1 and 3 months after surgery (P < .01 for all comparisons). Three months postoperatively, BSCVA was 1.13 and 1.10, respectively (P = .001). At that moment, 20 eyes (1.93%) in the LASEK group vs 9 eyes (0.84%) in the FSBK group had lost 2 or more lines of BSCVA. Ten eyes (0.96%) in the LASEK group gained 2 or more lines of BSCVA, whereas 3 eyes (0.28%) in the FSBK group gained 2 lines. Six months postoperatively, only 2 LASEK eyes (0.19%) showed loss of 2 or more lines of BSCVA, compared to 3 FSBK-treated eyes (0.28%).

CONCLUSION

Both FSBK and LASEK are safe and effective procedures to correct myopia. Slightly better visual and refractive results were observed in FSBK-treated eyes in a 3-month follow-up.