What does "in situ" mean when assessing contact lenses?

The term "in situ" when used in the context of assessing contact lenses refers to the lens being "in its original place," which, in this case, means on the eye for assessment. Conducting evaluations of contact lenses in situ allows practitioners to observe the lens's fit, movement, and interaction with the tear film and the ocular surface. This assessment is essential for determining lens performance and comfort during wear, as observations made with the lens on the eye can provide valuable insights that cannot be obtained when the lens is removed.

Furthermore, evaluating contact lenses in this specific scenario helps ensure that the lens is functioning as intended and that any potential issues, such as discomfort or deposits, can be identified and addressed properly. In contrast, the other options indicate scenarios where the lens is not on the eye, which would not provide the same level of insight into the lens's performance during actual use.