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The Girl With Unexplained Visual Loss
Ana* is an eight-year-old girl of Palestinian descent who was diagnosed several years ago with uveitis after experiencing pain in her right eye and blurry vision. She received treatment and was in good health until a year before we first saw her. At that time, she began having headaches and mouth sores. The headaches had prompted several emergency room visits, but the results of all tests had been normal. She had no other complaints, and her previous medical history was unremarkable, as was her family medical history. At this point, she was referred to our service.
We Get a Look
When we met Ana, she was thin but appeared healthy and was in no evident distress. Her BCVA was 20/25 in the right eye and 20/40 in the left. Her external examination, ocular alignment, motility, IOP, anterior segment and dilated fundus exam were normal.
We found no signs of past or present intraocular inflammation, although it was noted that Ana had aphthous ulcers on the roof of her mouth and on her tongue. Given her Middle Eastern descent, the previous diagnosis of uveitis and her oral ulcers, we recommended a rheumatologic workup for Behçet disease.
However, the rheumatologist regarded Ana’s oral lesions as “not typical of Behçet disease.” The relevant laboratory results were all normal, and an MRI scan of Ana’s brain showed no pathology. Ana was sent home.
A Series of Return Visits
A few weeks later, Ana returned to our office, complaining of pain in her left eye. At this visit, Ana’s VA was 20/20 bilaterally. Again, the comprehensive eye exam was unremarkable. Once again, we sent her home.
Two months later, Ana returned, complaining of decreased vision, ocular discomfort and photophobia. Again, the eye exam was normal, but her VA was 20/70 bilaterally. She did not identify any of the six Hardy-Rand-Rittler pseudoisochromatic color plates, including the test plate. Her pupils were equal, round and reactive, with no afferent pupillary defect.
We performed a fluorescein angiogram to rule out retinal vasculitis or hypoperfusion. In particular, we were concerned about the possibility of bilateral ischemic optic neuropathy in the setting of cerebral vasculitis associated with Behçet disease. However, the FA results were normal (Figs. 1 and 2).
Ana was admitted to the hospital and reevaluated by the rheumatologist. She received IV Solu-Medrol, at a dosage of 2 mg/kg, for three days. The workup, which included brain imaging, was negative. Moreover, while she was hospitalized, Ana noted a slight improvement in her vision. When we examined Ana, her VA at near was now 20/40 bilaterally; however, she still had decreased color vision.
The day after Ana was discharged from the hospital, she complained again of decreased vision. When we saw her again, her VA was 20/125 in the right eye and 20/80 in the left (20/30 and 20/40, respectively, at near). Apart from the VA measurements, this exam was unremarkable. Her color vision was normal—she could trace, but not name, the shapes on the color plates—and she had normal stereoacuity (40 seconds of arc).
At this point, we wondered whether Ana’s visual complaints had a nonorganic basis. We performed a “power refraction” (an elaborate procedure leading the patient to believe that complex corrective lenses are being used), and Ana’s VA improved to 20/20 with a –0.25 D spherical lens bilaterally.
We asked Ana’s mother about social stressors, psychological difficulties or family problems. She told us that she had separated from Ana’s father just before the onset of Ana’s complaints. Based on our findings and this information, we reassured Ana and her mother that Ana’s visual loss was not due to organic problems and that we expected her vision to return to normal. We asked them to return if any new issues came up. Since then, Ana has been doing well and has not had any additional complaints.
Behçet disease is a systemic inflammatory vascular disease characterized by recurrent oral and genital ulcers, skin lesions, arthritis and uveitis. The highest incidence is found in the Middle East and Asia. The primary ophthalmic manifestation is recurrent posterior uveitis; iridocyclitis, retinal/choroidal vasculitis, optic neuritis and retinal vascular occlusions also occur.1
Other manifestations of Behçet disease include musculoskeletal, vascular, gastrointestinal, renal, cardiopulmonary and neurologic symptoms. In one series, 17 of 22 patients had neurologic involvement, including sensory disturbances. 2 Visual symptoms were frequently reported as the initial presentation in neuro-ophthalmic cases.
Although cases of optic neuropathy in patients with Behçet disease have been described, few of them were retrobulbar. Retrobulbar optic neuropathy is a severe complication of Behçet disease. In this setting, ocular structures appear normal, but blindness can develop if the condition is left untreated. Retrobulbar optic neuropathy is thought to be a result of optic nerve ischemia, manifesting with decreased vision and often a central scotoma. Early treatment with immunosuppressants is crucial.3 Retrobulbar optic neuropathy should always be considered in patients with Behçet disease (or any other vasculitis) who present with an acute decrease in vision.
Solving the Mystery
The term functional visual loss (FVL) refers to subnormal vision without evidence of underlying pathology. The main categories of FVL include somatoform disorders, factitious disorders and malingering.
Evaluation of visual loss should begin with differentiating monocular from binocular visual loss, followed by eliciting whether the visual loss is primarily central or peripheral. Inconsistencies in the clinical findings or in the patient’s responses usually alert the astute physician that the visual loss may not be organic in nature. Techniques are then tailored to evaluate for FVL, depending on the patient’s complaints.
Many techniques are available, including the optokinetic nystagmus drum and the mirror test. The presence of stereoacuity will suggest at least some vision in both eyes (and some degree of binocularity); it is important to obtain visual fields to better characterize the patient’s deficits and to assess for consistency; and a power refraction can lure the patient into volunteering a better VA than had been obtained previously.4
Some patients with FVL have underlying psychiatric disease. In a study of 140 patients, 39 percent of adults and 18 percent of children with FVL had a psychiatric history.5 Another study of 71 children with FVL found that 27 percent had psychiatric disturbances, while 31 percent had significant home or school stress. Interestingly, 23 percent wanted glasses.6
FVL is not a diagnosis of exclusion; the physician has to prove that the patient’s vision is better than he or she claims. Therefore, visual loss should not be labeled as functional until this proof has been obtained.