Harada-Ito procedure
Encyclopedia
The Harada-Ito procedure is an eye muscle operation designed to improve the excyclotorsion
experienced by some patients with cranial nerve IV palsy. In this procedure, the superior oblique tendon is split, and the anterior fibers -- the fibers most responsible for incyclotorsion
-- are moved anteriorly and laterally. This selectively stretches and tightens these fibers, enhancing the incyclotorsion power of the superior oblique.
The most common indication for the Harada-Ito procedure is bilateral acquired cranial nerve IV palsy following closed head trauma (particularly automobile accidents). In this clinical situation the vertical imbalance is often less symptomatically bothersome to the patient than the induced excyclotorsion. Affected patients have a particularly annoying type of double vision (diplopia
), wherein the images are twisted (excyclotorted).
Patients with cranial nerve IV palsy whose complaints are not specifically limited to torsional diplopia, but instead also have significant vertical diplopia, are not good candidates for a Harada-Ito procedure. Instead, a recession of the inferior oblique muscle, or another strabismus
operation may be indicated.
Excyclotorsion
Excyclotorsion is a term applied to the outward, torsional movement of the eye, mediated by the inferior oblique muscle of the eye. The inferior oblique muscle is innervated by cranial nerve III .- Pathophysiology :...
experienced by some patients with cranial nerve IV palsy. In this procedure, the superior oblique tendon is split, and the anterior fibers -- the fibers most responsible for incyclotorsion
Incyclotorsion
- Physiology :Incyclotorsion is a term applied to the inward, torsional movement of the eye, mediated by the superior oblique muscle of the eye...
-- are moved anteriorly and laterally. This selectively stretches and tightens these fibers, enhancing the incyclotorsion power of the superior oblique.
The most common indication for the Harada-Ito procedure is bilateral acquired cranial nerve IV palsy following closed head trauma (particularly automobile accidents). In this clinical situation the vertical imbalance is often less symptomatically bothersome to the patient than the induced excyclotorsion. Affected patients have a particularly annoying type of double vision (diplopia
Diplopia
Diplopia, commonly known as double vision, is the simultaneous perception of two images of a single object that may be displaced horizontally, vertically, or diagonally in relation to each other...
), wherein the images are twisted (excyclotorted).
Patients with cranial nerve IV palsy whose complaints are not specifically limited to torsional diplopia, but instead also have significant vertical diplopia, are not good candidates for a Harada-Ito procedure. Instead, a recession of the inferior oblique muscle, or another strabismus
Strabismus
Strabismus is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely...
operation may be indicated.