Which factor is crucial when assessing tear film stability during lens fitting?

When evaluating tear film stability during contact lens fitting, the use of fluorescein dye is essential as it allows for a visual assessment of the tear film and the overall health of the ocular surface. Fluorescein dye, when applied to the eye, highlights the tear film and can help identify areas of dryness, irregularities, or insufficient tear distribution. This is particularly useful in pinpointing any issues that may affect the comfort and fit of the contact lenses.

By examining how the fluorescein disperses over the cornea and whether there are any areas where it pools or does not spread evenly, practitioners can gauge the stability of the tear film. A stable tear film is critical for optimal contact lens performance, as it affects both comfort and vision.

While factors such as age, the color of the lens, and time of day can influence comfort and vision-related issues, they do not provide direct measurement or assessment of tear film stability. Therefore, fluorescein dye remains a crucial and practical tool in this specific aspect of contact lens fitting.