Refractive surgeries performed with femtosecond (FS) lasers produce better dry eye outcomes at 3 and 6 months following thin-flap post laser in situ keratomileusis (LASIK) than procedures using mechanical microkeratome (MK), according to a study published in Eye and Contact Lens.
While prior research has indicated that FS technology has reduced intraoperative flap complications and improved control of flap parameters, dry eye remains common after LASIK. The objective of the current study was to compare the dry eye outcomes following FS-LASIK and MK-LASIK, which each had planned 100 mm flap thickness for eyes.
The study included 55 patients who were candidates for LASIK correction of myopia and had spherical equivalent up to -10 D, corneal thicknesses of at least 500 mm, and residual stromal bed of at least 300 mm.
They underwent LASIK using either FS (n=52 eyes, 22 bilateral and 8 unilateral patients) or MK (n=50 eyes).
In FS-LASIK, hinge was superior at 90° with a fixed flap diameter of 9 mm and side cut angle of 90°. In MK-LASIK, hinge was variable between 8 mm and 9 mm based on keratometry and fixed acute side cut angle. Flap thickness was planned to be 100 mm for both FS-LASIK and MK-LASIK.
Mean postoperative flap thickness was 103.65±5.54 or FS-LASIK and 124.44±4.48 for MK-LASIK (P =.001).
All dry eye parameters worsened at the third month before improving at the sixth month, without returning to pre-LASIK values.
Patients who underwent FS-LASIK had milder dry eye compared with those who underwent MK-LASIK, based on ocular surface disease index (OSDI) scores. Patients in the FS-LASIK group had higher mean tear break-up time (TBUT), Schirmer I, lower tear meniscus height (TMH), and tear meniscus area (TMA) compared with individuals in the MK-LASIK group at 3 and 6 months after the surgery.
Post-LASIK refractive outcome was similar in both groups.
At 6 months after surgery, depth of ablation and Schirmer I were inversely associated (r=-0.21 P =.039). Depth of ablation was linked with OSDI scores at 3 and 6 months after surgery (r=0.41 P <.001).
Other studies have indicated less evident dry eye features following FS-LASIK compared with MK-LASIK may be the result of more predictable uniform thin flaps with less damage to anterior corneal stroma innervation and faster recovery of corneal sensation, the researchers said.
“Although LASIK surgery is a well-known risk factor for developing dry eye disease, the use of femtosecond laser technology in performing thin-flap LASIK eye surgeries has improved the outcome of post-LASIK dry eye when compared with the mechanical microkeratome,” researchers explain.
Limitations of the study included those related to the effect of the flap/corneal diameter ratio on LINE development and dry eye outcome in both groups. The study lacked corneal sensitivity testing and corneal sub-basal nerve imaging.
Abdel-Radi M, Abdelmotaal H. Thin-flap laser in situ keratomileusis-associated dry eye: A comparative study between femtosecond laser and mechanical microkeratome–assisted laser in situ keratomileusis. Eye and Contact Lens. 2022;48(1):20-26. doi:10.1097/ICL.0000000000000850