OPTIC NERVE AVULSION

In an avulsion of the optic nerve, the nerve is torn or partially torn posteriorly from its insertion into the retina at the level of the lamina cribrosa. This disinsertion or retraction of the nerve is due to a mechanical shearing force on the posterior aspect of the globe.

Symptoms

Patients present following head trauma that may be severe or seemingly minor. Visual acuity is often no light perception if the avulsion is complete; visual acuity may be better (20/100 to light perception) if the avulsion

is partial. Patients have no pain associated with the avulsion; although, pain may be present due to external injuries.

Clinical Features

Patients with optic nerve avulsion typically have evidence of external trauma and will frequently have symptoms from an injury to the orbit. The normal optic disc is replaced by a depression or cavity, with surrounding and overlying hemorrhage. The amount of intraocular hemorrhage may be massive. The optic disc cavity is eventually replaced with glial tissue.

Ancillary Testing

Computed tomography may be necessary to rule out an intraorbital or intraocular foreign body. Neuroimaging is, however, unreliable in making the diagnosis of optic nerve avulsion.

Pathology/Pathogenesis

The optic nerve is “tethered” at its posterior entry site into the globe. The mechanism of injury at the level of the lamina cribrosa is likely due to a complete disruption of the ganglion cell axons as they exit the globe. Because the rectus and oblique muscles support the globe and hold it in a relatively static position, a sudden and rapid displacement of the nerve may shear the nerve from the posterior wall of the globe. In addition, a rapid forward pulling of the globe may also cause the nerve to avulse posteriorly. Rapid rotational eye movements have also been implicated as a primary mechanism for optic nerve avulsion.

Treatment/Prognosis

Treatment for optic nerve avulsion is supportive and conservative. The prognosis for vision is extremely poor. Final visual outcome is usually dependent on the initial visual acuity after injury. Surgical intervention is not warranted unless a rupture of the globe is suspected.

Systemic Evaluation

Careful attention to associated orbital, maxillofacial, cranial, and cervical injuries is warranted.

Acute optic nerve avulsion following a finger injury to the orbit. The optic disc is replaced by a large depression with hemorrhage extending throughout the retina and vitreous.

Fundus photograph following partial optic nerve avulsion. There is intraretinal, preretinal, and vitreous hemorrhage. Note the folds radiating from the

optic disc.

Following the acute injury, fibroglial proliferation occurs in and around the optic disc region and may extend into the vitreous cavity.

The vitreous hemorrhage may be diffuse or localized in the region of Cloquet’s canal.

PURTSCHER’S RETINOPATHY

In 1910, Austrian ophthalmologist Otmar Purtscher described a retinopathy of bilateral peripapillary patches of retinal whitening and hemorrhages in patients who suffered massive head trauma. The term Purtscher’s-like retinopathy has been used to describe similar fundus findings in association with other conditions, including pancreatitis, kidney disease, childbirth, cancer, and autoimmune disorders (systemic lupus erythematosus, scleroderma, dermatomyositis).

Symptoms

Patients generally experience rapid, painless, and profound visual loss in both eyes. Occasionally, the symptoms will be quite asymmetric or unilateral. The patients may note Amsler grid changes or central scotoma.

Clinical Features

A bilateral decrease in visual acuity and central visual field that corresponds to the degree of retinal involvement occurs in these patients. An afferent pupillary defect may be present if the condition is unilateral or asymmetric. The acute funduscopic appearance includes large patches of ischemic retinal whitening and intraretinal hemorrhages surrounding the optic disc. Optic nerve head swelling is typically absent. Over several weeks to months, the ischemic whitening fades, and the hemorrhages resolve. Late findings include arteriolar narrowing and nerve fiber layer atrophy in the ischemic area as well as optic nerve pallor.

Ancillary Testing

Visual acuity measurements and visual field testing may be helpful in documenting the extent of retinal involvement. Fluorescein angiography typically demonstrates a lack of capillary blood flow in the regions that correspond to the areas of ischemic retina. Indocyanine green angiography demonstrates areas of choroidal nonperfusion that may persist for months.

Pathology/Pathogenesis

The precise mechanism for Purtscher’s retinopathy remains unknown. Microembolic theories remain the leading candidates for the pathogenesis of these ischemic retinal changes surrounding the optic disc. There is evidence that complement activation leading to leukocyte emboli may occlude the peripapillary retinal capillaries. Unilateral Purtscher-like retinopathy also has been described as a complication of local injury, either facial trauma or retrobulbar anesthesia.

Treatment/Prognosis

Treatment for Purtscher’s retinopathy is supportive and directed at the underlying medical conditions. The ischemic retinal patches and retinal hemorrhages will resolve gradually. Final visual acuity depends on the level of retinal involvement and ranges from normal to severely reduced.

Systemic Evaluation

In the setting of trauma, other injuries should be evaluated and imaged as appropriate. In the absence of obvious trauma, a more thorough systemic evaluation should include testing for acute pancreatitis, disseminated intravascular coagulopathy, autoimmune disorders, pregnancy, renal function, thrombotic thrombocytopenic purpura, and hemolytic-uremic syndrome.

Purtscher’s-like retinopathy in a woman with scleroderma. There are peripapillary superficial white patches, few intraretinal hemorrhages, and a normal optic disc.

Fluorescein angiography of Purtscher’s retinopathy reveals hypofluorescence corresponding to the white patches that results from blockage and capillary nonperfusion.

The fellow eye of the same patient demonstrates numerous superficial white patches concentrated around the optic disc. Note that the white patches obscure the underlying retinal vessels.

Venous phase angiogram demonstrates persistent hypofluorescence corresponding to the nonperfusion and areas of hyperfluorescence from retinal vascular leakage.

This 7-year-old boy had severe Purtscher’s-like retinopathy following a presumed viral-induced dermatomyositis associated with acute renal failure. The fellow eye appeared similar.

Unilateral Purtscher’s-like retinopathy after a motor vehicle accident; the patient experienced chest compression injury and a long bone fracture. The visual loss was permanent.