Final answer:
The typical optical zone diameter in an Ortho-K lens is around 6 mm, designed to cover the average pupil size in various lighting conditions, although the exact diameter can vary based on individual needs.
Step-by-step explanation:
The question pertains to the typical optical zone diameter in an Orthokeratology (Ortho-K) lens. Ortho-K lenses are specially designed contact lenses that temporarily reshape the cornea to reduce or correct myopia (nearsightedness). The diameter of the optical zone in Ortho-K lenses is an important factor because it must adequately cover the pupil to correct vision properly during both day and night.
The average human pupil size can vary from around 2 mm in bright light to approximately 7 mm in the dark. Therefore, Ortho-K lenses typically have an optical zone diameter of about 6 mm to ensure that the pupil is covered in most lighting conditions. However, the exact diameter can vary depending on individual patient needs and the lens design prescribed by the optometrist.