Pattern visual evoked potential in the diagnosis of functional visual loss1
Section snippets
Subjects and methods
A retrospective study was performed on 138 subjects who were suspected of having FVL and referred to the electrophysiologic laboratory at the Vitreoretinal Foundation for VEP from 1991 to 1999. The records of these subjects, including medical history, clinical examination, visual fields (VFs), fluorescein angiography, ultrasonography, magnetic resonance imaging, computed tomography, x-ray studies, laboratory tests results, VEP, and consultant letters, were reviewed. Subjects were referred to a
Results
In a total of 72 subjects, unilateral visual loss was noted in 25 subjects and bilateral visual loss in 47 subjects. The VAs of both eyes were similar in bilateral visual loss subjects. The initial best-corrected subjective VA ranged from 20/50 to no light perception. The VA was 20/50 in 9 subjects and ≤20/200 in 42 subjects (Fig 1). The P-VEP estimated VA ranged from 20/30 to 20/100 and was 20/30 in 43 subjects, 20/50 in 25 subjects, and 20/100 in 4 subjects. Comparing the subjective VA and
Discussion
When a subject complains of vision loss or VF loss that is inconsistent with the physical, objective examination of the eye and visual system, FVL should be suspected. Ocular hysteria and malingering are two major forms of FVL. Hysterical amblyopia subjects manifest visual loss unconsciously. Some have underlying organic problems with functional overlay. Some show psychiatric or psychosocial problems, yet in most no origin could be disclosed.9, 10, 12, 13, 14 Malingering subjects often have
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Cited by (36)
Functional (Nonorganic) Visual Loss
2018, Liu, Volpe, and Galetta's Neuro-Ophthalmology: Diagnosis and ManagementFunctional neuro-ophthalmology
2011, Handbook of Clinical NeurologyCitation Excerpt :We have seen numerous patients with visual acuity of 10/100–20/400 in one eye and 20/20 in the fellow eye who have had no RAPD by standard clinical testing, but whose visual-evoked responses were bilaterally delayed, indicating a bilateral optic neuropathy. Thus, if there is no indication of functional disease in a patient with unexplained, unilateral visual loss without an obvious RAPD, such a patient should undergo electrophysiological testing, particularly full-field and multifocal electroretinography and pattern reversal and flash-evoked, visual-evoked potentials (Nakamura et al., 2001; Xu et al., 2001; Raghunandan and Buckingham, 2008). It must be remembered that, although electroretinography is an objective test of overall retinal function, visual-evoked responses elicited by pattern reversal may be affected by a variety of factors other than organic disease of the central visual pathways (Towle et al., 1985).
Feigned Visual Loss Misdiagnosed as Occult Traumatic Optic Neuropathy: Diagnostic Guidelines and Medical-legal Issues
2009, Survey of OphthalmologyCitation Excerpt :Unprofessional, offensive characterizations in the expert IME report could possibly provoke litigation against the expert for libel but certainly demonstrate a manifest lack of objectivity and will result in loss of the expert's credibility if and when the expert report is presented at trial. Electrophysiologic tests, such as visual evoked potentials (VEP) and electroretinogram (ERG), respectively, can provide objective diagnostic evidence of loss of optic nerve or retinal function2,14 but are of very limited clinical usefulness in cases of feigned visual loss because they can be voluntarily suppressed.7,13 Thus a normal VEP is confirmation of good optic nerve function, but a flat VEP may be the result of voluntary suppression.
The utility of clinical electrophysiology in a case of nonorganic vision loss
2008, OptometryCitation Excerpt :Chan et al.18 claimed that most scaling methods using pVEP responses for predicting visual acuity perform quite poorly. On the other hand, Xu et al.19 showed that the discrepancy between the predicted acuity based on pVEP responses and the best-performed Snellen acuity was less than 3 lines in 87.5% of subjects with NOVL. Furthermore, even though a normal pVEP response is strongly suggestive of NOVL,2,12,15,20 it does not unequivocally preclude the existence of organic disease.
Pattern Visual Evoked Potentials in the Assessment of Visual Acuity in Malingering
2007, OphthalmologyCitation Excerpt :A tendency of the P100 component to broaden or decrease in amplitude suggests that accommodation or fixation is unsatisfactory. A short break from testing and comforting words can improve test results.10 All PVEP recordings in our study were recorded by an experienced ocular electrophysiology technician.
Visual Evoked Potentials in Pediatrics-Abnormal
2006, Clinical Neurophysiology of Infancy, Childhood, and Adolescence
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The authors have no proprietary interest in any of the materials used in this study.