TBUT by Biomicroscopy
blinks
BLACK SPOT, CORNEA
After fluorescein instillation, subjects were asked to blink naturally to spread the fluorescein over the surface of the cornea. Using the cobalt blue filter and a wide beam on the biomicroscope the cornea was examined to establish that the fluorescein was spread evenly. Once the fluorescein between blinks appeared evenly spread, the subject was asked to open the eyes, maintain primary gaze, and not to blink. The interval between opening the eye and the appearance of the first dark or black spot or region over the cornea was recorded in seconds for Tearfilm Break-up Time. After determination of the TBUT, the same procedure was performed on the contralateral eye.