(1) An elevation of the adducted eye in the absence of a significant hypertropia in primary position is commonly referred to as an upshoot in adduction.  It is fallacious to believe that every apparent overaction in the field of action of the inferior oblique muscle is, in fact, an overaction of that muscle.  Failure to recognize that a variety of different conditions may produce a similar clinical picture may lead to the wrong diagnosis and the wrong therapy.

(2) The first step in analyzing the problem is to observe and then to measure whether the elevation is limited to adduction or exists in other gaze positions as well.  Special attention should be paid to any other overacting or, perhaps, underacting muscles as the patient maintains fixation with either eye in the diagnostic positions of gaze.

(3) Upshoot, downshoot, or both on attempted adduction may be a feature of Duane syndrome type I and, more commonly, of types of II and III (see 2.50, 2.51 and 2.52).

(4) This upshoot in adduction is caused by a primary or secondary overaction of the inferior oblique muscle.  This muscle is unopposed by its paretic antagonist.  The difference in vertical deviation on tilting the head to the right and left shoulder (Bielschowsky test, see 2.14) is measured with the prism cover test.  During the measurement the base of the vertical prism must be held before the eye, parallel to the inferior orbital rim.

(5) The Bielschowsky test is positive for a right superior oblique palsy when the right hypertropia increases with the head tilted to the right shoulder.

(6) In primary overaction of the inferior oblique muscle, the function of the superior oblique is usually normal.  This condition is often bilateral and accompanied by a V pattern esotropia in downward gaze.  Unlike in bilateral superior oblique paralysis, the Bielschowsky test is negative.

(7) Because the secondary deviation is always greater than the primary deviation, the left eye must be the paretic eye (see 1.08).

(8) The Bielschowsky head tilt test may be helpful in identifying paretic vertical rectus muscles (see 2.14).

(9) See 2.37.

(10) In dissociated vertical deviation (DVD) (see 2.16), elevation of the involved eye occurs from primary position, abduction, and adduction.  Although this elevation is usually more pronounced in abduction, it may be present to an equal degree in adduction.

(11) Unlike in secondary inferior oblique overaction where underaction of the antagonist of the yoke muscle (LSR) is the rule, that muscle acts normally when a patient with DVD fixates with the involved eye in elevation and abduction.

(12) See 2.16.