This observational study aims to compare two laser corrective procedures for treating myopia and myopic astigmatism: a novel refractive technique, the CLEAR procedure, and the established SMILE procedure. Participants will be randomized to undergo CLEAR in one eye and SMILE in the other. The investigators will evaluate and compare the two procedures based on the following aspects: refractive predictability (how accurate the vision correction is) by measuring the proportion of eyes close to the target prescription after surgery, clinical dry eye outcomes, changes in tear proteins, and corneal nerve changes at 1, 3, 6, and 12 months after both surgeries. Metabolomic features of the removed corneal tissue and how precisely the laser is centered during surgery will also be examined. Our hypothesis is that CLEAR provides equally good vision results as SMILE, and explore any extra benefits of CLEAR.
>/= 21 years of age and </= 50 years of age.
Cycloplegic spherical equivalent of >-1.00D
Refractive cylinder -2.00 D or less; anisometropia <1.00D
Best spectacle corrected visual acuity (BSCVA) of 6/12 or better in BOTH eyes.
Progressive or unstable myopia and/or astigmatism.
Clinical or corneal topographic evidence of keratoconus.
Patients who want bilateral SMILE procedure
Patients who want extracted corneal lenticule to be stored for future refractive surgery.