Why is the use of Wratten #12 or Tiffen yellow filter important in evaluating the fluorescence pattern of patients with GP lenses?

The use of Wratten #12 or Tiffen yellow filters is crucial when evaluating the fluorescence pattern of patients wearing gas permeable (GP) lenses because these filters effectively block certain wavelengths of light, particularly short-wave ultraviolet (UV) light. This is significant in the context of evaluating the fluorescence pattern, which can be indicative of how well a lens is fitting and whether it is interacting appropriately with the tear film.

When these filters are used, they eliminate the interference from fluorescence induced by UV light, which can obscure the actual fluorescence that is coming from the dye used during the evaluation process—often fluorescein. By blocking out this distracting fluorescence, the practitioner can gain a clearer view of the actual fluorescein pattern, which is essential for determining lens fit, identifying any potential issues such as apical bearing, and assessing overall ocular health.

This focused view allows for a more accurate assessment of how the lenses sit on the eye, making it an important practice in contact lens fitting and evaluation.