Injury in One Eye Followed by a Hyperopic Shift in the Other

Discussion

SO is a rare, bilateral, granulomatous uveitis that occurs after surgical or accidental trauma to one eye.^[1] The injured eye is referred to as the exciting eye and the uninjured eye as the sympathizing eye. Inflammation in the sympathizing eye can develop weeks to years after the trauma. Epidemiologic estimates have shown the incidence after penetrating ocular injury to be 0.2% to 0.5% and after intraocular surgery to be 0.01%.^[2] Even though trauma has been the most common precipitating event, ocular surgery is now considered a more common risk factor, particularly cyclodestructive and/or intraocular surgery.^[3,4]

This patient sustained a significant traumatic injury to the right eye and developed SO 2 months after her open-globe injury. Approximately 65% of SO cases occur 2 weeks to 2 months after the injury, and 90% occur in the first year. Cases of SO occurring as early as 5 days and as long as 66 years after an injury have been reported.^[5,6]

Prompt diagnosis using patient history and initial clinical findings and proper treatment are important for saving vision in patients with SO. The earliest symptoms of SO can include loss of accommodation, photophobia, floaters, and epiphora. The loss of accommodation in our patient was related to the presence of choroidal thickening and subretinal fluid with hyperopic shift. Eyes with SO can also have anterior uveitis with mutton-fat keratic precipitates, posterior synechiae, elevated intraocular pressures, and vitritis. Histopathologic findings in SO are the same in the exciting and sympathetic eyes. An associated exudative retinal detachment is very common.

A key presenting sign in SO is small (60-700 µm in size) yellow-white chorioretinal lesions called Dalen-Fuchs nodules. These lesions create a diffuse, non-necrotizing inflammatory infiltrate in the uveal tract. Histopathologically, there is lymphocytic infiltration with nests of macrophages, granuloma, epithelioid cells, and multinucleated giant cells. The Dalen-Fuchs nodules containing these cells are located between the Bruch's membrane and the retinal pigment epithelium. Typically, the inflammation spares the choriocapillaris and retina.

Although the Dalen-Fuchs nodules have been thought to be pathognomonic for SO, they can be found in sarcoid choroiditis and VKH. Fluorescein angiography might not be needed to diagnose SO, but it can be helpful in confirming the diagnosis when it reveals multiple sites of choroidal leakage that correspond to the Dalen-Fuchs nodules. On fluorescein angiography, the nodules cause early hypofluorescence with late leakage and eventual pooling of dye under the serous retinal detachment, as was seen in our patient.^[7,8]

The etiology of SO is still not completely understood; however, it is believed that injury to the uveal tract instigates an autoimmune inflammatory response directed against ocular self-antigens. The exact autoantigens have not yet been determined, but retinal S-antigen, melanin-associated antigens, and antigens derived from the retinal pigment epithelium and choroid are believed to be involved.

In the past, enucleation of the exciting eye 10 to 14 days after the penetrating injury was frequently recommended to prevent SO. However, this has become more controversial because modern advanced surgical techniques combined with aggressive immunosuppressive therapy can help maintain good vision in both eyes. The treatment of SO is systemic immunosuppression. High-dose systemic corticosteroids are typically the first-line treatment, and doses from 1 to 2 mg/kg per day are tapered over 3 to 4 months. Some initially resistant cases of SO might benefit from intravenous pulse steroid therapy (methylprednisolone 1 g/day for 3 days) and require corticosteroid-sparing agents, as our patient did.

Depending on long-term needs, corticosteroid-sparing agents can include azathioprine, methotrexate, mycophenolate mofetil, and even cyclosporine, chlorambucil, and cyclophosphamide.^[9] Because many of these immunosuppressive agents can have significant systemic adverse effects, frequent monitoring of possible toxic reactions and the collaborative management of the patient with an internist or rheumatologist is recommended. It is not uncommon for systemic immunosuppressive medications to be combined with topical corticosteroids and cycloplegics to prevent anterior uveitis and synechia formation.

Even though SO can lead to vision loss and phthisis bulbi, aggressive immunosuppressive therapy and advanced surgical techniques for ocular injuries have improved our ability to prevent blindness in this debilitating disease. Over the past quarter of a century, the prognosis of SO has dramatically improved, with more than 50% of eyes maintaining 20/50 vision and 75% maintaining better than 20/200 vision. Ocular complications, such as cataract, secondary glaucoma, and maculopathy, can be treated, and most patients with SO can maintain functional visual acuity with appropriate management and follow-up.^[10]

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