The Harada–Ito procedure is an

eye muscle The extraocular muscles (extrinsic ocular muscles), are the seven extrinsic muscles of the human eye. Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye and the o ...

operation designed to improve the

excyclotorsion Eye movement includes the voluntary or involuntary movement of the eyes. Eye movements are used by a number of organisms (e.g. primates, rodents, flies, birds, fish, cats, crabs, octopus) to fixate, inspect and track visual objects of interests ...

experienced by some patients with

cranial nerve IV palsy Fourth cranial nerve palsy or trochlear nerve palsy, is a condition affecting cranial nerve 4 (IV), the trochlear nerve, which is one of the cranial nerves. It causes weakness or paralysis of the superior oblique muscle that it innervates. This co ...

. In this procedure, the

superior oblique The superior oblique muscle, or obliquus oculi superior, is a fusiform muscle originating in the upper, medial side of the orbit (i.e. from beside the nose) which abducts, depresses and internally rotates the eye. It is the only extraocular musc ...

tendon is split, and the anterior fibers – the fibers most responsible for

incyclotorsion Eye movement includes the voluntary or involuntary movement of the eyes. Eye movements are used by a number of organisms (e.g. primates, rodents, flies, birds, fish, cats, crabs, octopus) to fixate, inspect and track visual objects of inte ...

– 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 A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of inju ...

(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 is the simultaneous perception of two images of a single object that may be displaced horizontally or vertically in relation to each other. Also called double vision, it is a loss of visual focus under regular conditions, and is often v ...

), 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 The inferior oblique muscle or obliquus oculi inferior is a thin, narrow muscle placed near the anterior margin of the floor of the orbit. The inferior oblique is one of the extraocular muscles, and is attached to the maxillary bone (origin) and ...

muscle, or another

strabismus Strabismus is a vision disorder in which the eyes do not properly align with each other when looking at an object. The eye that is focused on an object can alternate. The condition may be present occasionally or constantly. If present during a ...

operation may be indicated.

References

* Metz H, Lerner H: The adjustable Harada–Ito procedure. Arch Ophthalmol 1981;9

* {{DEFAULTSORT:Harada-Ito procedure Eye surgery

See also

References