“For standing Āsana it is not necessary to close the eyes.
As standing Āsana are usually at the beginning of a practice,
it can sometimes be distracting to close the eyes,
because of all the visual activity proceeding the practice.
Having the eyes open can also stop you becoming unbalanced as you move.
The eyes can be useful for checking alignment within dynamic movements.
You may not observe this with the eyes closed.
However, the attention with the eyes open should be passive and aware.”
– TKV Desikachar 1980