 Four-year-old male who approximately three weeks ago began having horizontal binocular dyplopia Which was gradually worsening and therefore came for evaluation of this So we're going to have you look straight ahead as you will notice here the patient does have an exotropia And in doing a cover test keep looking straight ahead I did our red dot here And you'll see look straight ahead at the red dot straight ahead at the red dot So an alternating exotropia Okay, again follow Follow the red dot here everywhere it goes Just without holding your head steady Okay, you'll notice that as we move across the right eye will not go past the midline But the left eye follows and here's moving across again the left eye goes slightly past the midline, but will not abduct completely This is a very typical inter nuclear ophthalmoplesia You'll also notice as we move out that the abducting eye or the eye turning out will occasionally show some abduction misdiagnosis All the red dot everywhere it goes. You see a few beats of abduction misdiagnosis Follow the red dot vertical movements Are grossly normal other than the fact that the without full adduction He's unable to Get the eyes into all vertical positions. Now. We're going to have you look back and forth look right at my finger and now at the red dot The finger and the red dot you'll notice as he looks back and forth that there is a lag of Adduction look at the finger now at the red dot finger red dot Finger You'll notice as we do that that that left eye lags over and the right eye goes over quickly But the left eye lags over slowly look at the red dot now at the finger Red dot and finger red dot Right here look at the finger Red dot and finger Very good Once again following the red dot you'll notice the lack of adduction far past the midline with either eye Very good. We'll watch as he converges look right at the red dot again Okay Best you can look right at the red dot try to bring it in and focus on that red dot So he gets some element of convergence there look right at the red dot You can see he's able to Slightly bring it in Start again here Focus as best you can on the red dot There you see every so often he can momentarily gain or close to gain fusion the reason for that being that the convergence mechanisms are not damaged as much as the Horizontal gaze mechanisms, which is from the intra nuclear