Pattern electroretinogram plus visual evoked potential: A decisive test in patients suspected of malingering

Abstract

Along the processing chain in the visual pathway the pattern electroretinogram (PERG) is a better indicator of the peripheral function than the visual evoked potential (VEP). Therefore the PERG and the VEP will be impaired equally by disturbances before the ganglion cell layer (e.g., blurred image or retinal disease) and differently by further centrally located diseases (e.g., tumor compression of the optic nerve). Thus in patients complaining of reduced visual acuity who show disturbed VEP but a normal PERG, malingering can be definitely ruled out. Representative combinations of PERG and VEP findings are described.

Functional Visual Loss

“…Voluntary alteration or obliteration of evoked potentials is not uncommon and may be inapparent even to a trained observer [25, 27]. A similar situation exists with pattern and multifocal electroretinograms: a normal and symmetric response argues against the presence of severe organic disease and an abnormal test is inconclusive [28, 29, 30]. The flash electroretinogram measures the function of predominantly the outer retinal layers of cells involved in vision.…”

Assessment of patients with suspected non-organic visual loss using pattern appearance visual evoked potentials

“…Under such circumstances, observing the P100 component during acquisition, which tends to sharpen in an alert, concentrating patient will reveal a tendency to broaden with apparent latency increase when concentration is poor. In addition, simultaneous recording of the PVEP and PERG can be used, since a normal PERG recording will confirm the patient to be focusing on the stimulus [33].…”

Pattern-reversal visual evoked potentials as a diagnostic tool for ocular malingering

“…For example, a patient might not focus on the center of the screen or might close his/her eyes too frequently. However, these artifacts were controlled through a careful observation of patient behavior during testing, as described in another report (19) . In some cases, mainly those of patients who reported a lack of light perception, the use of flash VEPs might be considered to avoid the requirement for constant and steady eye fixation.…”