Clinical electrophysiology of the retinal pigment epithelium

Abstract

There is no ideal electrophysiological test for retinal pigment epithelial (RPE) function. The light-induced responses (EOG, c-wave, fast oscillation) that require photoreception are not pure RPE signals, and even the widely-used EOG has not been associated with any specific physiological disturbance of the RPE or retina. The discovery of non-photic RPE responses (hyperosmolarity, acetazolamide and bicarbonate) has enhanced the possibility of finding tissue-specific RPE tests, but these responses have yet to be correlated with specific RPE functional activity or pathology. We may face a dilemma in our search for RPE tests, insofar as electrophysiology measures membrane changes, but RPE membrane activity is related only indirectly to many functions of the RPE cell. These concerns notwithstanding, RPE electrophysiology can be a valuable clinical tool if one accounts for the physiological limitations and assets of the procedures.

Alcohol- and Light-induced Electro-oculographic Responses: Variability and Clinical Utility

“…In addition, intra-individual variations in Li-EOG from normal subjects are also wide [25][26][27], thereby making it difficult to use for assessing changes in a single patient (unless a series of recordings were to be done). It may be time to re-evaluate the clinical utility of Li-EOG, not only relative to its few disease correlations beyond Best dystrophy [6] (e.g. ADVIRC [34], which is another bestrophin disease, and the staging of AZOOR [35]), but to its inter-and intra-individual variability.…”

“…Several stimulating agents have been used, including hyperosmolar fluids, acetazolamide and sodium bicarbonate. However, these non-photic responses, much as the light EOG response, have shown clinical variability and no specific correlation with most diseases involving the RPE [6].…”

“…However, while there are striking EOG abnormalities in Best's vitelliform dystrophy [5], EOG responses in other disorders of the RPE have been markedly variable [6]. This includes inconclusive results in age-related macular degeneration (ARMD) [7][8][9][10] as well as normal responses in central serous chorioretinopathy (CSC) [11][12][13] and rubella retinopathy [14].…”

Light-Evoked Responses of the Retinal Pigment Epithelium: Changes Accompanying Photoreceptor Loss in the Mouse

“…However, it has been reported that disorders that include severe RPE abnormalities (such as rubella retinopathy and diffuse drusen) are not associated with changes in RPE electrophysiology, as evidenced by normal or mildly affected electrooculogram and nonphotic responses (Gupta and Marmor 1994;Marmor 1991). Each dc-ERG component reflects the activity of ion channels that undoubtedly play many roles in maintaining retinal homeostasis.…”

Exploration de la fonction visuelle sensorielle chez l'animal : Deuxième partie : ERG chez l'animal

“…Chez les espèces nocturnes, l'état d'adaptation à l'obscurité sera obtenu au bout de plusieurs heures (BEHN et al, 2003). En ce qui concerne l'état d'adaptation à la lumière chez l'homme et les espèces animales diurnes, il est considéré comme stable au bout de deux heures, si la rétine a préalablement été exposée un temps très long à l'obscurité (MARMOR, 1991). Néanmoins, en pratique, on peut considérer que si l'éclairement rétinien est constant et uniforme pendant 10-15 minutes, il est possible d'obtenir un état d'adaptation photopique stable (GOURAS et MACKAY, 1989).…”