how to determine eye dominance

Here’s a simple dominant eye test to determine which eye is your preferred eye:

Extend your arms out in front of you and create a triangular opening between your thumbs and forefingers by placing your hands together at a 45-degree angle (see animation).
With both eyes open, center this triangular opening on a distant object — such as a wall clock or door knob.
Close your left eye.
If the object stays centered, your right eye (the one that's open) is your dominant eye. If the object is no longer framed by your hands, your left eye is your dominant eye.

Here’s another easy dominant eye test:

Extend one arm out, holding the thumb of that hand in an upright position. (Or you could use your index finger instead of your thumb.)
Keeping both eyes open and focused on a distant object, superimpose your thumb on that object. (Don't worry if it looks like your thumb partially disappears — that's normal.)
Alternately close one eye at a time.
The eye that keeps your thumb directly in front of the object while the other eye is closed is your dominant eye.

Both of these dominant eye tests are categorized as “sighting” tests, since they involve aligning a visual target with a makeshift sighting device (mimicking the “sight” on the barrel of a rifle).