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-56- Binocular Vision & Inferior Oblique Muscle Palsy with ‘Paradoxical’ V-Pattern Strabismus FIRST Quarter of 2011 Strabology Quarterly© E. Khawam, MD and D. Fahed, MD Volume 26 (No.1) A Medical Scientific e-Periodical Pages 51-60 b. Head Turn: commonly seen, to the shoulder of the opposite side placing the eye in the field of the lesser vertical deviation, away from the vertical field of fixation of the IO muscle, placing the affected eye in abduction. c. Abnormal Chin Posture: less commonly encountered than head tilt. In esodeviation with an A-pattern to the deviation, the patient may assume a chin-up posture to avoid the esodeviation in upgaze. In A-exotropia, the patient may assume a chin-down posture to avoid exodeviation in down-gaze. 7. Forced Head Tilt Test (Bielschowsky’s Sign): The head must be tilted to the opposite shoulder in order to cause maximal vertical deviation. With tilting to the opposite shoulder, both extorters of the eye in the opposite side are stimulated. Since the IO muscle is paretic, its elevating action cannot offset the depressing action of the IR muscle, resulting in increasing hypotropia of the affected eye. 8. Raising-Eye Phenomenon of the Fellow Eye in Abduction: The mechanism of this phenomenon is as follows: in adduction of the affected eye, excessive innervational input is sent to the paretic IO muscle in order to balance that eye vertically. Therefore, a corresponding, equal, excessive innervation goes to its yoke SR muscle via Hering’s Law. This increased innervational input to the SR of the contralateral eye in abduction causes upshot or rising of that eye. 9. Duction versus Version: In palsy of an extraocular muscle, the action of that muscle improves on duction compared to its action on version. A characteristic that does not pertain to mechanical restrictions. CASE REPORT This is a 67-year-old woman referred to us because of diplopia and right hypotropia of 3-years duration (Figure 3 A, Below and 3 B, Next Page). Figure 3 A (Khawam & Fahed): Our patient in 8 of the 9 cardinal gaze positions. Figure 3 B (Khawam & Fahed): Our patient in Bielschowsky Head Tilt Test.
-57- Binocular Vision & Inferior Oblique Muscle Palsy with ‘Paradoxical’ V-Pattern Strabismus FIRST Quarter of 2011 Strabology Quarterly© E. Khawam, MD and D. Fahed, MD Volume 26 (No.1) A Medical Scientific e-Periodical Pages 51-60 Retinoscopy revealed +1.50 Diopters and +1.00 Diopter of refractive error in the right and left eyes respectively. Visual acuity with her correction was 20/80 OU. Cover testing in the primary position with correction disclosed 16 prism diopters (PD) of right hypotropia (HoT) with 3 PD of exotropia (XT) at distance, and 12 PD of right HoT with 3 PD XT at near. Cover testing in upgaze revealed 25 PD of right HoT with 16 PD of XT, and in downgaze 10 PD of right HoT. In left gaze, cover test showed 30 PD of right HoT and 7 PD of XT, decreasing in right gaze to 6 PD of right HoT. Above, in Figure 3 B, on head tilt test, to the right shoulder, (left frame) there was 12 PD of right HoT. On head tilt to the left shoulder, (right frame) the right HoT increased to 30 PD. On versions, patient showed a -3 underaction of the right IO muscle, a very pronounced overaction of the right SO muscle, the right eye shooting down on levoversion (Figure3, top, this page). When monocular ductions were performed, the right eye improved substantially its elevation in adduction. When the patient looked down on adduction, in the field of action of the right SO muscle, the left IR muscle appeared underacting by virtue of Hering’s Law of equal (lesser) innervation (Inhibitional Palsy of Chavasse). Indeed, the underaction of the left IR muscle was only seen when the right eye (Figure 4, below, left frame) fixes in adduction and depression, but disappears on duction, (right frame). Double Maddox rod testing revealed 6 degrees of incyclotropia. Figure 4 (Khawam & Fahed, stretched): Left, our patient showing underaction of the left inferior rectus muscle in version, but, right, not on duction , on gaze down-and-left.
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