Did you know that you also have a form of diplopia all the time but you are not aware of it?

Physiologic diplopia, or “normal double vision”, is a phenomenon in which objects are doubled, either in front of or behind the focused target.

You can see this for yourself with a simple demonstration:

• Select a distant target.
• Extend your arm and place your thumb in between you and the target.
• Look at the distant object, your thumb will be doubled.
• Now change your focus to the thumb and the distant object will be doubled. Normally our brains and we do not notice this doubling. On the sub-conscious level, the brain actually uses the difference in the double vision in front of and behind the target object to help with determining depth perception.

Occasionally, we will have a very astute patient notice this phenomenon and come to the eye clinic for evaluation. First we need to investigate if what they are actually noticing and describing is physiologic diplopia. If so, and if the rest of the eye exam is normal, we can be reassured this is normal.

Double vision is more worrisome when what you are trying to focus on goes double. This could be a sign of strabismus/squint. It is important to have a full evaluation of the eye if you notice double vision to make sure there is nothing wrong.