Functional Visual Loss and Malingering

S. Trauzettel-Klosinski

Malingering is an intentionally deceptive mimicry of a nonexistent disorder, and augmentation is an intentionally exaggerated account of an existing disorder. Functional visual loss is a subjectively described visual disorder without an objectively observed abnormality. It is an unconscious, often subconscious, simulation of a nonexistent disease. (Synonyms include psychogenic visual loss, conversion, and hysterical visual loss). The related group of psychogenic ocular disorders includes functional disease, psychosomatic disease, and artificial eye diseases. Psychosomatic eye disease is initiated by a psychically triggered (or heavily influenced) organic disease with demonstrable pathological findings, as for example, in some reported cases of glaucoma, uveitis, or central serous retinopathy. Artificial eye diseases arise by self-inflicted trauma (autoaggression) and have demonstrable pathological findings during the eye examination. This type is usually associated with psychoses or so-called specific personality disorders. Simulation and functional visual disturbances are characterized by a tendency to mask themselves. The specific diagnosis is important, however, so that the patient will not be unjustly classified as a simulator on the one hand, and on the other hand, to spare the patient with functional disease any unnecessary and expensive tests, to avoid the development of additional symptoms, and to provide the patient with appropriate help. This chapter covers the clinical presentation, the differential diagnosis, and the specific ophthalmic diagnosis of these disorders. The most important principles are addressed here, although a more complete description and extensive bibliography are provided in Trauzettel-Klosinski (see Trauzettel-Klosinski [1997a, b] under "Further Reading").

Flow diagram. Test sequence for the differential diagnosis of a visual disturbance without a morphological correlate (modified from Trauzettel-Klosinski S [1997] Untersuchungsstrategien bei Simulation und funktionellen Sehstörungen. Klin Monatsbl Augenheilkd 211: 73-83)

Examination Strategies for Functional Visual Loss and Malingering

Although functional visual loss and malingering have very different origins and therefore require very different therapeutic measures, they produce identical clinical appearances and can be unmasked by the same methods. The term "malingering test" is used in the following sections as a generic term for the investigational strategies to be used in cases of feigned visual loss, independent of the disorder's cause.

Differential Diagnosis

It is not usually the patient's behavior, but rather a poorly described visual complaint with no apparent morphological correlate, that first suggests a nonorganic disorder. First, organic ocular and visual disorders that can present without related physical findings must be specifically ruled out of the differential diagnosis (â–  Table 15.1).

Note

The diagnosis of functional or simulated visual loss cannot be made purely as a diagnosis of exclusion. A positive finding is required. Specific malingering tests must be used in the differential diagnosis.

Visual impairment of unknown cause without morphological correlates should cause the examiner to begin a systematic examination process that will clarify the diagnosis (see the accompanying flow diagram and Chap. 2). If poor visual acuity is not improved by use of the best spectacle correction or a pinhole aperture, the problem is not an optical one. If monocular visual loss is not accompanied by an associated relative afferent pupillary defect, there is no optic neuropathy. If there is no amblyopia (stereopsis, no stra bismus, no anisometropia, central fixation), there are no signs of macular disease (fundoscopy, perimetry, fluores-cein angiography, foveal fixation), and there is a normal visual field and color vision is normal, then suspicion of a feigned visual disturbance should initiate a series of malingering tests.

In many instances, suspicion is raised during the initial stages of the examination based on contradictory findings. One can then turn directly to a sequence of malingering tests. Unusual visual field defects should lead to a quick assessment of their reproducibility. In cases of a central scotoma, normal pupillary light reactions, unremarkable visually evoked potentials (VEP), or normal results on flicker testing as described by Aulhorn will effectively rule out a retrobulbar optic neuritis with a high level of certainty, see Trauzettel-Klosinski (1989) and Chap. 8. Concentric visual field constriction with a cylindrical or tubular profile (constant size of field at all distances from the eye), or spi-raling isopters found during kinetic perimetry, strongly suggests a nonorganic disturbance. The same applies to constriction of the visual field coupled with normal elec-troretinography (ERG) responses and no signs of bilateral occipital disease.

Feigned hemianopic visual field defects are occasionally encountered. Suspicion is aroused when no pathology is found on CT or MRI scans (often brought in by the patient from recent prior evaluations), also when homonymous hemianopia is not accompanied by reading problems (see below and Chap. 24). Other differential diagnostic considerations may be suggested when a patient complains of transient visual loss and then yields varying results during repeated examinations. Such patients are sometimes mistakenly categorized as malingerers. For this reason, it is especially important to clarify the nature and the source of the problem, saving the physician time wasted and the patient unjust accusations.

Table 15.1. Visual loss with no apparent morphological correlate: Hidden disease? Functional disorder? Malingering?

Table 15.1. Visual loss with no apparent morphological correlate: Hidden disease? Functional disorder? Malingering?

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