SMILE results in less dry eye symptoms than LASIK

Researchers compared dry eye metrics and corneal nerve morphology in patients undergoing SMILE and femtosecond laser-assisted LASIK (FS-LASIK).

Study design

The study included 16 patients undergoing FS-LASIK and 13 undergoing SMILE who were followed for 1 month. They assessed ocular surface disease index, dry eye questionnaire 5-items (DEQ-5), tear film osmolarity, tear meniscus height, noninvasive keratograph breakup time (NIKBUT), ocular staining and meibomian gland atrophy. An automated analysis of corneal nerve parameters was evaluated using confocal microscopy with ACCMetrics software (University of Manchester).

Outcomes

Visual and refractive outcomes were comparable between groups. The FS-LASIK arm reported increased dry eye symptoms compared with SMILE (P<0.05). In addition, the authors noted a significant decrease in tear meniscus height and NIKBUT after FS-LASIK (31% and 40%, respectively) but not after SMILE. Both procedures affected corneal nerve fiber density, corneal nerve branch density, corneal nerve fiber length (CNFL), and corneal nerve fiber fractal dimension, however the impact was significantly greater with FS-LASIK (P=0.001). Only CNFL correlated with the reported symptoms after FS-LASIK (r =−0.545).

Limitations

The sample size was small and the follow-up period was only 1 month.

Clinical significance

Although both procedures lead to good refractive and visual outcomes, the findings suggest FS-LASIK has a greater impact on dry eye disease symptoms and corneal nerve anatomy than SMILE. Employing a fully automated approach to quantifying corneal nerve fiber morphology when using confocal microscopy may be advantageous in identifying the impact of refractive surgery on corneal nerves.