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Answers: 2004 series -  August 31, 2004 Lecture 18 of 50  NEXT»

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This 7-year-old boy had surgery one year ago for comitant esotropia that measured 20 prism diopters.  Both medial rectus muscles were recessed 3.5 mm from the original insertion.  His family reports that his eyes drift upward when he is tired.  They also note that his eyes deviate outward when he looks down.  Vision is 20/20 in each eye.  Refractive error is +1.50 sphere in each eye.  He does not wear glasses.

1.  This patient has an "alphabetic pattern" of vertical incomitance described as:    
 

b -- This is an "A" pattern of vertical incomitance.  An "A" is said to be present when there are 10 prism diopters more exodeviation (less esodeviation) in 30 degrees downgaze compared to 30 degrees upgaze measured in the distance with full correction and accommodation suspended.

2.  In downgaze it would appear that there is overaction of the:  
 

a -- In downgaze there is apparent overaction of the superior oblique muscles.  This does not imply increased generated force, but simply states that the action of these muscles is exaggerated.  This is so in this case because of the effect of the prior medial rectus recession which puts the abducting and extorting action of the superior oblique muscles at an advantage. 

3.  The view of the eyes behind the translucent occluder demonstrates: 
  c -- This is clearly a case of dissociated vertical deviation.  The exact cause of this is not known.  Various theories have attempted to explain it without universal agreement.



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