Hi @me-supachai, thanks for your query. Unfortunately, the Unity SDK does not include a blink detection algorithm nor is individual eye validity exposed programmatically.
You could in theory create your own custom blink detection algorithm within using a loop counter of around 200ms based on gaze validity, but this may not provide the most accuracy for your needs. Accordingly, if you need access to individual eye validity data, you will need to use the Tobii Stream Engine API for these purposes.
Please also bear in mind that using either the Unity SDK or Stream Engine API for analysis or research requires the purchase of an analytical licence to do so.
You can read more about this @ https://analyticaluse.tobii.com/
If you could kindly describe in more detail your project intentions, we will do our best to help you out! Best Wishes.