Final answer:
The most common complication associated with ortho-K is infections, and maintaining proper hygiene is crucial to prevent them.
Step-by-step explanation:
The question pertains to the common complications associated with orthokeratology (ortho-K), which is a non-surgical process that uses specially designed contact lenses to temporarily reshape the contour of the cornea to improve vision. Among the choices provided, the correct answer is C. Infections; hygiene. It is critical for patients undergoing ortho-K treatment to maintain excellent hygiene to avoid ocular infections, such as microbial keratitis. This is why healthcare professionals will emphasize the importance of proper lens care and handling, as well as regular monitoring to catch any complications early on.