Comparison of corneal sensitivity, tear function and corneal staining following laser in situ keratomileusis with two femtosecond laser platforms

Andrea Petznick,¹ Annabel Chew,² Reece C Hall,² Cordelia ML Chan,² Mohamad Rosman,^1,2 Donald Tan,^1–3 Louis Tong,^1–4 Jodhbir S Mehta<sup>1–3

1</sup>Singapore Eye Research Institute, Singapore; ²Singapore National Eye Centre, Singapore; ³Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; ⁴Duke-NUS Graduate Medical School, Singapore

Purpose: To evaluate longitudinal changes in corneal sensitivity, tear function, and corneal staining in patients who underwent laser in situ keratomileusis (LASIK) using two different femtosecond lasers.
Methods: In a prospective, randomized clinical trial, contralateral eyes of 45 patients underwent flap creation by either VisuMax or IntraLase™ femtosecond laser. Corneal sensitivity, tear break up time (TBUT), Schirmer’s test, and corneal fluorescein staining were assessed preoperatively and at 1 week, 1 month, and 3 months postoperatively.
Results: There were no statistical differences in any clinical outcome measure between the two femtosecond lasers (P > 0.05), although there was a trend towards slightly lower reductions for corneal sensitivity and TBUT in VisuMax-operated eyes. Overall, corneal sensitivity was significantly reduced at 1 week (P < 0.05), 1 month (P < 0 .001), and 3 months (P < 0.001) postoperatively. A significantly greater reduction of corneal sensitivity was noted in eyes with a myopic spherical equivalent of −6.00 diopters (D) to −11.25 D as compared with eyes that had a relatively lower level of myopia of less than −6.00 D (P < 0.001). TBUT and Schirmer’s test values were significantly diminished at 1 week postoperatively (P < 0.04). Overall, corneal staining was significantly increased at 1 week postoperatively (P < 0.001). The level of myopia did not significantly affect postoperative changes in TBUT, Schirmer’s test values, or corneal staining (P > 0.05).
Conclusion: This study showed that changes in corneal sensitivity, tear function, and corneal staining were statistically similar in LASIK using VisuMax and IntraLase femtosecond lasers for flap creation. However, the trend towards faster recovery of corneal sensitivity and TBUT observed in VisuMax-operated eyes may be attributable to improved technical specifications.

Keywords: femtosecond laser, corneal sensitivity, tear film break-up time, Schirmer’s, corneal staining