The use of femtosecond (FS) laser in LASIK procedures for myopia correction can lead to the formation of an opaque bubble layer (OBL) in stromal layers of different densities and in various areas of the cornea.

PURPOSE

This study evaluated the functional outcomes and the condition of the cornea in eyes with and without OBL in randomized groups.

MATERIAL AND METHODS

The study included 93 patients (186 eyes) with varying degrees of myopia (from 2.25 to 7.5 D): the main group consisted of 137 eyes with OBL, the control group — 49 eyes without OBL. The average age of patients was 30±5 and 32±4 years, respectively, with spherical equivalent refractive errors of –4.9 D and –4.3 D, astigmatism up to 1.75 D and 1.25 D, respectively. The assessment included uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), clinical refraction, lower-order aberrations (RMS LOA), higher-order aberrations (RMS HOA), spherical aberration (Z40; Pentacam HR Oculus), confocal microscopy of all corneal layers, and tear film assessment (Medmont; TFSQ; TFBUT; TFSQ area). All patients underwent FS-LASIK [Technolas VICTUS; corneal flap thickness of 110—120 μm (optical zone 6.0 mm), pulse energy >1 mJ, frequency 80 kHz]. Follow-up visits were conducted at day 7, and 1, 3, and 6 months.

RESULTS

No statistically significant differences were observed between the groups in terms of functional outcomes and optical aberrations. However, the OBL group showed significantly higher TFSQ values and more pronounced keratocyte changes visualized in the deep stromal layers (under the OBL) at the depth of 130—160 μm. The extent of keratocyte alterations decreased over time, from 118.3±5.1 mm/mm² on day 7 to 71.1±4.8 mm/mm² at 6 months, as observed via confocal microscopy.

CONCLUSION

While there was no difference in functional outcomes for myopia correction between eyes with and without OBL, the presence of OBL was associated with a higher extent of destructive changes in keratocytes, necessitating a longer healing period.