Which factor can impact TFBUT results?

• A. The color of the eye.
• B. The time of day only.
• C. The patient's diet.
• D. Volume and Concentration Issues: can impact results.

Answer: (D)

The key idea is that TFBUT is a measurement of tear film stability that can be biased by how the dye is administered. The amount (volume) and strength (concentration) of fluorescein you place on the eye can change the tear film’s properties and how well you can visualize breakup. If you use too much dye or a high concentration, it can irritate the surface or provoke reflex tearing and alter blinking, potentially shortening or otherwise distorting the measured breakup time. If you use too little dye or a very dilute solution, visualization can be poor, making it hard to detect the first sign of breakup and leading to an inaccurate (often longer) reading. Because these procedural factors directly bias the test outcome, volume and concentration issues reliably impact TFBUT results. Other factors like eye color, time of day, or diet don’t have a meaningful direct effect on the tear film breakup time in standard testing.