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Lights On-Off Test
a.k.a. Small field central fusion test
- This test is useful in the setting of diplopia in the presence of a dragged fovea causing diplopia giving central-peripheral rivalry
- Use a single white letter on a black monitor about 20/70 in size
- Must have a very dark room and no light bleeding through an LCD monitor
- The patient sees diplopia when fixating on the letter with the lights on
- With the lights off, the diplopia resolves
