Boston XO (Hexafocon A), Boston XO2 (Hexafocon B)

The Boston XO and Boston XO2 lenses are explicitly designed for daily wear as part of corneal reshaping therapy, not overnight wear. This means they are meant to be worn during the day for vision correction and removed at night. The lenses are intended for professional fitting in controlled clinical settings, where specific fitting techniques and protocols must be followed to ensure safe and effective use, as outlined in the accompanying professional guides.

The Boston XO and XO2 lenses are supplied as non-sterile devices, meaning they are not pre-sterilized for direct patient use. This requires clinicians to follow strict hygiene protocols, including proper cleaning, disinfection, and storage procedures before fitting them to a patient. Since they are single-use, each lens must be handled in a sterile environment to prevent contamination before application.

The key difference between the Boston XO and Boston XO2 lies in their composition: the XO2 variant includes an ultraviolet absorber (either Uvinul D-49 or MHB), which provides added protection against UV exposure during wear. Clinicians may choose the XO2 if UV protection is a priority for their patient, particularly in settings where prolonged sun exposure is common, while the XO may be preferred for its simpler formulation.

The lenses are supplied as single-use devices, meaning each lens is intended for one patient application only. This design reduces the risk of cross-contamination and infection, but it also requires clinicians to maintain an adequate inventory of different sizes and models to accommodate varying patient needs. Since they are non-sterile, proper storage conditions must be maintained to preserve their integrity until use.

The Boston XO and XO2 lenses have undergone FDA 510(k) clearance (K171404) and comply with EU MDR requirements, confirming their authorization for use in both the U.S. and European markets. Their classification as Class II medical devices under FDA regulations (21 CFR 886.5916) indicates they are subject to stricter controls than lower-risk devices but do not require the same level of oversight as Class III. This regulatory route ensures they meet safety and performance standards for professional fitting in clinical settings.