The inferior oblique muscle was subjected to surgery as early as 1841, but for myopia! By 1885, inferior oblique weakening for treatment of superior oblique palsy was done. The muscle was exposed through a skin incision and the muscle was cut medial to Lockwood's ligament. This technique persisted into the middle of the twentieth century. After that, more attention was directed to weakening the muscle distal to Lockwood's ligament nearer the insertion. Currently the most effective techniques for inferior oblique weakening include myotomy, myectomy, and recession, placing the new insertion at various positions in the inferior temporal quadrant according to the surgeon's preference. Surgical techniques for inferior oblique weakening also vary in the extent to which the inferior oblique is freed from its union with Lockwood's ligament and in the management of the neuro-vascular bundle.
In order to avoid surgery on the inferior oblique in some cases of overaction, Bielschowsky was said to have lowered the medial rectus. This portended treatment of ‘A’ and ‘V’ pattern with vertical shift of the rectus muscles and possibly the description of the pulleys of the rectus muscles whose anomalous location leads to vertical incomitance.
Recently, inferior oblique anterior transposition has been used for the treatment of inferior oblique ‘overaction’ especially when it is associated with dissociated vertical deviation (DVD). The mechanism of action for this treatment of DVD has been explained by Stager who demonstrated that the robust neurovascular bundle of the inferior oblique is effective in anchoring the transposed inferior oblique insertion. This is the same neurovascular bundle that was cut by Parks during the denervation and extirpation procedure for maximum weakening of the inferior oblique.
Myectomy or large recession of the inferior oblique distal to the muscle’s attachment at Lockwood's ligament makes this attachment equivalent to the new functional insertion (Figure 35). Although not done now, earlier procedures for weakening the inferior oblique, which were carried out nasal to the ligament of Lockwood, meant that the inferior oblique union with Lockwood’s ligament became the functional origin. A procedure described by Stager and Weakley transected the inferior rectus on both sides of Lockwood's ligament relying on a small segment of the middle of the muscle stabilized by Lockwood's and the neurovascular bundle. In cases of ‘extirpation and denervation’ of the inferior oblique, a large myectomy of the distal inferior oblique is combined with transection of the neurovascular bundle.
Figure 35
The inferior oblique behaves as if it had two potential origins and two potential insertions because of its union with Lockwood's ligament as it passes beneath the inferior rectus. In addition, at the mid-section of the inferior oblique is a stout neurovascular bundle, described in detail by Stager and associates, which acts both as a restraining anchor and a source of innervation.
The inferior oblique is unique among the extraocular muscles in that, in many cases, weakening of this muscle, even by extensive surgery, seems to have relatively little effect on movement of the globe or alignment of the eyes. Even after large recession or myectomy, apparent overaction of the inferior oblique can persist. This is probably due to horizontal rectus action from upward pulley displacement of the medial rectus. Also, in the relatively uncommon inferior oblique paresis, strabismus is much less than would occur after paresis of any of the other muscles. Effective weakening of this muscle could be made more difficult because of the unique anatomy. Likewise neurologically, the muscle’s innervation by the inferior branch of cranial nerve III makes isolated paralysis rare. In contrast, the inferior oblique seems to ‘overact’ commonly. But is ‘overaction’ the right term? Some think it is not, suggesting that the preferred term would simply describe appearance not etiology. The term "elevation in adduction," which replaces the Latin "strabismus sursoadductorius," seems to be a valid description of what has been called ‘overaction’ of the inferior
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