Most patients with vertical deviations demonstrate some lateral incomitance. However, in vertical deviations not associated with apparent oblique muscle dysfunction, the difference between the deviations in right gaze and left gaze is usually less than 10Δ.
Monocular Elevation Deficiency
Monocular elevation deficiency (previously termed double-elevator palsy) involves a limitation of upward gaze with a hypotropia that is similar in adduction and abduction. There are 3 forms of this motility pattern, each with a different cause: restriction of the inferior rectus muscle; deficient innervation of elevator muscles (paresis of 1 or both elevator muscles or a monocular supranuclear gaze disorder); a combination of restriction and elevator muscle deficit.
All 3 forms of monocular elevation deficiency are characterized by hypotropia of the involved eye with limited elevation, a chin-up head position with binocular fusion in downgaze, and ptosis or pseudoptosis (Fig 11-6). True ptosis is present in 50% of affected patients. These are features of third nerve palsy, as well. Therefore, if any other feature of third nerve palsy is present, that condition should be suspected rather than monocular elevation deficiency.
The clinical features of each form of monocular elevation deficiency are as follows:
Figure 11-6 Monocular elevation deficiency of the left eye. Top row, No voluntary elevation of the left eye above horizontal. Second row, Hypotropia of the left eye across the horizontal fields of gaze. Third row, Depression of the left eye is unaffected. Bottom row, left, Ptosis (true and pseudo-) of the left upper eyelid during fixation with the right eye (in the top 3 rows, the left upper eyelid is elevated manually). Bottom row, center, Persistence of ptosis and marked secondary overelevation of the right eye during fixation with the left eye. Bottom row, right, Bell phenomenon, with the left eye elevating above the horizontal on forced eyelid closure.
In support of this classification, studies using magnetic resonance imaging have shown either focal thickening of the inferior rectus muscle, supporting a restrictive etiology, or normal ocular motor nerves, suggesting a central unilateral disorder of upgaze.
Indications for treatment include a large vertical deviation in primary position, with or without ptosis, and an abnormal chin-up head position. If restriction originating inferiorly is present, the inferior rectus muscle should be recessed. If there is no restriction, the medial and lateral rectus muscles can be transposed toward the superior rectus muscle (Knapp procedure). Alternatively, the surgeon can recess the ipsilateral inferior rectus and either recess the contralateral superior rectus muscle or resect the ipsilateral superior rectus muscle. Ptosis surgery should be deferred until the vertical deviation has been corrected and the pseudoptosis component eliminated.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.