A Prospective, Randomized, Double-blinded, Controlled, Split-face, Non-inferiority Clinical Investigation Comparing the Safety and Performance of RefillHA Solid With Hydryalix Ultra Deep Lidocaine for the Correction of Moderate-to-severe Nasolabial Folds.

Inclusion Criteria: * Men or women of any race, 18 years of age or older. * The presence of moderate to severe bilateral NLFs each with WSRS score of 3 or 4. * NLFs of the same WSRS grade on the left and right sides of the face. * Willing and able to read, understand and sign the informed consent. * Willing to adhere to the protocol and to comply with the requirements of the entire investigation (ability to attend all the planned investigation visits according to the time limits included and report events and concomitant medication for the entire duration of investigation). * Agree not to undergo other treatments or cosmetic procedures in the treatment area during the study, such as botulinum toxin, hyaluronic acid injections, facial laser treatments, fat injections, any other permanent or semi-permanent facial dermal fillers. * Female subjects of childbearing potential must have a negative urine pregnancy test and must adopt an appropriate method of contraception for the entire duration of investigation. Exclusion Criteria: * Pregnant (as determined by a urine pregnancy test at the screening visit) or lactating women. * Prior treatment (i.e., other permanent or biodegradable injectable fillers or surgical correction such as a face-lift, etc.) within 3 months prior to entry into the study or planned to undergo such treatment during the study. * Previous treatment with permanent implants (e.g., silicone) in the area to be treated. * Subjects who are currently or recently tr…