Please look at the light and tell me what you see
Patient: I see two lights that are side by side
Assistant: Now I am going to move the lights closer together. Tell me if you still see two lights or if they merge into one.
Patient: As you move the lights closer, they are now merging into one light.
Assistant: Thank you. That demonstrates you do not have diplopia in primary position. Now I am going to move the light up, down, left, and right. Please tell me if you see one light or two lights as I move it to different positions.
This tests for diplopia in different gazes which helps localize the site of the problem causing diplopia