Tear Film, Optics, and Biomechanics After Small-Incision Lenticule Extraction: Preliminary Study
To quantitatively measure the change in tear film, the optical quality and corneal biomechanics post SMILE (Small Incision Lenticule Extraction) refractive surgery.
Fifty eyes of 25 subjects undergoing SMILE for myopia and myopic astigmatism were subjected to Lipiview interferometer for assessment of lipid layer thickness in the tear film. The modulation transfer function cutoff frequency, the Strehl ratio, the width of the point spread function (PSF) at 10% of its maximal height (PSF10), and the width of the PSF at 50% of its maximal height (PSF50) were analyzed to asses the optical quality using a double pass technique. Air-puff applanation by Scheimpflug-based dynamic tonometer was done to evaluate the corneal biomechanics before and after the SMILE surgery.
Preliminary results showed no significant difference in any of the parameters in pre operative and 1-week postoperative visit. There was an improvement observed in the optical quality on subsequent visits. Analysis of corneal biomechanics revealed no differences in radius at highest concavity (HC radius), time until first applanation (A1 Time), time until second applanation (A2 Time), and deflection length at highest concavity (HC deflection length). Dry eye after surgery is usually transient. The study is on going.
Small incision lenticule extraction procedure revealed better patient comfort and comparable dry eye parameters. The procedure alters the corneal biomechanical properties that is not significant.