What if they struggle to see the physiological diplopia?

In some cases, especially with strabismus and/or amblyopia, the patient will not be aware of a second image. 

They can still be shown how to see physiological diplopia, but you have to begin where they are.

Most will have a favorite eye. 

Ask the patient to block (not close) an eye.  Usually, they will block the one they believe is worst.

Ask them to line up the pencil with the doorknob and move the pencil in and out while keeping the pencil and the doorknob in line.

Have them uncover the other eye.  Does it look different—usually no.

If yes and they see physiological diplopia, you can begin to work towards centering the pencil and proceeding with the process in the more usual fashion.

Have them cover the favorite eye and do the same “tromboning” as before.

This may be a bit more difficult as they are probably not used to leading through the least favorite eye. 

What happens when you uncover your other eye?

If they tell you, “Wow, there’s another one.”, That’s great, but doesn’t always happen.

Often, they will move their hand in front of the favorite eye without knowing they have done so.

In those cases, we have to help them become aware of the images in a more static fashion.

Recover the favorite eye and have them hold the pencil aligned when looking through the least favorite eye.

Tell them to freeze—don’t move a muscle except to uncover their other eye.

Some will still try to move the pencil in front of the favorite eye.  You may have to help them by gently holding their pencil hand still. 

Once they can accept that the pencil is aligned with the doorknob through the least favorite eye, they can almost always be aware of another doorknob off to the side. 

Now we go back to slight tromboning movements keeping the least favorite eye aligned while being aware of the “extra” doorknob. 

With practice they can become aware of the extra doorknob and can even shift from side to side keeping the pencil aligned with either doorknob as they wish.

It is then time to go ask the person to put the pencil exactly in between the two doorknobs and watch how the doorknobs change position as the patient follows the pencil.  

Once they can put the pencil between the two doorknobs, it is time to go through the rest of the activity.

Traditional diagrams of visual alignment say that we align our eyes at a given point and will see double if the eyes are not aligned unless the image produced through one of the eyes is suppressed.

We know this is not really true because we don’t see double very often in life.

We see the world in solid 3D—something we need two pictures to accomplish.

Physiological Diplopia occurs when the person is unable to  organize the visual world in the usual fashion or we ask them to organize the world in an unusual fashion. 

It happens in the brain, not in the eyes.

This activity lets us help the patient investigate their own visual process by looking in an unusual way. 

Activity

Have the patient hold up a near target—a pencil will do—while looking across the room at a target such as a doorknob.

What do you notice about the pencil while looking at the doorknob? 

Hopefully, they will see two pencils—If so, ask them where the two pencils are. 

If they see two pencils on either side of the doorknob, ask them what happens if they tilt their head a little bit.

Can you make the two pencil tips level with one another? 

What happens if you move the pencil closer or farther from your face?  Can you find a way to put the pencils you see on each side of the door? 

Now look at the pencil.  How many doorknobs are there? 

We go through much the same kind of sequence as when looking at the doorknob, except now we are looking at the pencil and seeing two doorknobs. 

An important aspect of this activity is play.  Enjoy learning about how vision works.

Note:  This is not an antisuppression activity.  We are teaching a person to organize the field in a new way and to be able to manage how they organize their visual volume.

Home Practice

Every aspect of this can be practiced at home.

Once you identify the level you believe will afford the patient the opportunity to grow and develop best with this activity over the following week, feel free to assign that as home practice and exploration.