Automatic Fluorescein Break Up Time Detection in Dry Eyes (or Demonstrating the difficulty of estimating the BUT)

AIM: To automatically measure the fluorescein break up time (FBUT) without the intervention of a clinician and to define a new standard called Digital Break Up Time (DBUT), which is the automated version of the FBUT. METHODS: 22 patients with varying degrees of dryness have been examined. A small amount of fluorescein (the size of a DET strip) is instilled in the patient's eye and is instructed to keep his eyes open as long as possible. Using the Eye-Scan fluorescein tear film module, we record a video from blink to blink. These videos are used as input to our new method to automatically detect dryness signs including the. The method consists of a multi-step algorithm, which first locates the iris in each image, then aligns the images in the video and finally analyzes the aligned sequence in order to find the DBUT. We define the DBUT as the first video frame after a blink when an area of a minimum size is completely devoid of fluorescein. We instructed two qualified clinicians to first go over the videos once as recorded and write the FBUT and then go over again as many times as needed and correct the FBUT if needed. Results: Comparing our DBUT to the corrected FBUT provided by the two clinicians, we received an accuracy of 2.4 +/- 1.8s and 3.7 +/- 4.2s. The inter observer accuracy was 3.5 +/- 2.7s. Considering the high inter observer differences, our results are well inside the acceptable range. The intra observer differences of the clinicians were (between their own measurements): 1.3 +/- 2.0s and 1.4 +/- 1.7s. The major inter and intra observer differences show that it is a hard task for the clinician to produce a correct FBUT and the need for the standardized DBUT exists. Conclusion: We showed that our method is capable of accurately detecting the FBUT for dry eye patients and the need for a unifying computerized standard for the FBUT detection.

Results

In the following example, 5 snaphsots are taken from a video. Next to each image, the timing after the blink is written. Which image do you think corresponds the best to the BUT?
The four images in the corners correspond to 4 different break-up-times provided by four different clinicians. The image in the middle corresponds to the image after 10 seconds, showing that the intensity of the breaks still increases.