5.        Blink Analysis: it uses template matching and statistical tools to process captured frames to detect and measure blinks. To start blink analysis, make sure that the correct eye is selected and click the start camera button.

1.        Switch to Blink Analysis mode. Device uses infrared light for blink analysis so you will not be able to see any illumination coming on. Click on the start camera button to start the test. Select a magnification (default is 1.2) so that the entire eye (from outer to inner canthus) is in the frame.
2.         You can select the duration of the test of blink to be 30 (recommended and default) or 60 seconds. You need to click the Set button adjacent to the time selector drop down to set the time of test to your selected value. Setting the duration of the test while the test is in progress will restart the test and should not be done.

3.         Your mouse will be automatically relocated to the Click to capture closed eye image button. The closed eye image (above figure) acts as a template image for the image processing tools to compare. It also defines a complete blink. If the patient has a constant lagophthalmos you can treat this as a closed eye image. Do not use any mechanical means to close the lids for a closed eye image. Click on the button to capture the closed eye image (the captured image appears above the button). If you are satisfied proceed to click the Start/re-start Blink Analysis button.
4.         It is vitally important for getting accurate data to have the patient’s head firmly fixed against the slit lamp forehead rest band and give the patient a distant target before taking the template image and starting the test. Too much ocular movement can give wrong results and movement of people in the field of view of the patient when performing the test should be avoided. The environment in the room should be calm and not noisy. Ask the patient to blink normally and click the Start/re-start Blink Analysis button.
5.         A live tracking graph will appear above the Start/re-start Blink Analysis button which will help you in understanding whether the test is progressing correctly with good quality data. Each blink produces a peak in the running graph, with an open eye causing the graph to fall back to the baseline. Ocular movements cause minor fluctuations in the baseline and should not be a cause for concern. However, if there are wide ranging ocular movements or if the patient moves away from the device it can cause erroneous or un-processable results. In such cases retake the template image and/or restart the test. A typical graph is shown below

 

6.         An acceptable graph will have mostly equal peaks and a relatively horizontal baseline. As mentioned above, the baseline will never be absolutely straight but should not tilt unduly up or down. If you are not happy with the graph restart the test.
7.         The time elapsed and number of frames captured will appear in bold red letters below the live window and give you an indication about the progress of the test.
8.         At the end of the test, if quality parameters are met, the various test statistics will be displayed and a “baseline-corrected” graph with baseline correction will be displayed (as below)

 

9.         Save the test by clicking the Save button on the main toolbar
10.     The various statistics of blink analysis are:
    1.                        Complete, incomplete (partial) blinks and the blink rate (per minute)
    2.                        Mean and standard deviation of blink durations (defined as open-eye-to-open-eye – not lid contact time) (in milliseconds)
    3.                        Mean and standard deviation of inter-blink intervals (in milliseconds)
    4.                        Lid contact time as a percentage of total test time – this is a measure of the time that the lids were in contact i.e. the eye was closed with larger values indicating a fatigued or dry eye