During slit-lamp evaluation, how can you assess if soft contact lenses fit well when the patient blinks?

When assessing the fit of soft contact lenses during a slit-lamp evaluation, observing the movement of the lenses during a blink is crucial. A movement of 0.5 to 1mm indicates that the lens is functioning properly and is well-centered on the cornea. This range of movement allows for adequate tear exchange under the lens, ensuring comfort and preventing the potential for complications such as lens binding to the cornea.

When the lens moves within this optimal distance, it suggests that it is not too tight or excessively loose. A lens that does not move at all may be too tight, potentially causing discomfort, and can lead to issues like corneal hypoxia or staining. Conversely, if the lens moves more than 1mm, this could signify a loose fit, which could risk dislodgment and negatively impact visual acuity.

In summary, a movement of 0.5 to 1mm is considered ideal in indicating that the soft contact lenses fit well, balancing both patient comfort and lens stability on the eye. This assessment is critical in ensuring the health and comfort of the patient while wearing contact lenses.