Electrophysiology and glaucoma: current status and future challenges

Abstract

Visual electrophysiology allows non-invasive monitoring of the function of most processing stages along the visual pathway. Here, we consider which of the available methods provides the most information concerning glaucomatous optic nerve disease. The multifocal electroretinogram (ERG), although often employed, is less affected in glaucoma than two direct measurements of retinal ganglion cell function, namely the pattern ERG (PERG) and the photopic negative response (PhNR) of the ERG. For the PERG, longitudinal studies have been reported, suggesting that this method can be used for the early detection of glaucoma; for the PhNR, no longitudinal study is available as yet. The multifocal PERG can spatially resolve ganglion cell function but its glaucomatous reduction is typically panretinal, even with only local field changes and so, its topographic resolution is of no advantage in glaucoma. The multifocal visual evoked potential promises objective perimetry and shows sensitivity and specificity comparable with standard automated perimetry but has not been established as a routine tool to date.

Electroretinography in glaucoma diagnosis

“…Nevertheless, the PERG is the most well established ERG technique for glaucoma diagnosis with a long proven history of efficacy (for thorough reviews of PERG historical background and utility for glaucoma diagnosis, see e.g.,[9, 22, 24–27]). The results of two recently published PERG studies in particular, however, warrant special consideration for their implications.…”

“…However, historically, the full-field flash ERG has not been useful for glaucoma diagnosis since it is dominated by the responses of neurons of the distal retina, namely photoreceptors and bipolar cells (though the OPs are thought to be generated by amacrine cell signal processing within the inner plexiform layer). Generally the full-field flash ERG does not reflect the responses of retinal ganglion cells (RGCs), which are the primary neuron affected by glaucoma [8, 9]. Though it remains a matter of some mild controversy, the evidence that outer retinal (e.g.…”

“…In contrast, the photopic negative response (PhNR) is much easier than the STR to record in a clinical setting and is similarly dependent on intact RGC responses [19–21]. The PhNR has thus proven to be an effective objective clinical diagnostic test for assessment of RGC function in optic neuropathies, including glaucoma (for excellent recent reviews, see Machida [21] and Bach and Poloschek [9]). There are additional types of ERG recordings based on alternative stimulus and recording paradigms rather than full-field flashes, such as the well known pattern reversal ERG (PERG) [22] and multifocal ERG (mfERG) [23], which can also be obtained in a routine clinical setting and offer meaningful objective measurements of RGC function in glaucoma [9].…”

The effects of immune protein CD3ζ development and degeneration of retinal neurons after optic nerve injury

“…The mouse was placed on a warming pad and monitored until it fully recovered from anesthesia. For the first three days after the procedure, systemic analgesics (buprenorphine) and topical antibiotic ointment were applied twice daily and the mouse was closely monitored for possible infection, bleeding, and loss of muscular control [24–26]. The effectiveness of the injury of RGC axons was confirmed by CTB labeling of the optic nerve 1 week after the ONC.…”

Detection of Early Age-Related Macular Degeneration Using Novel Functional Parameters of the Focal Cone Electroretinogram

“…Components of the waveform, such as the “a” and “b” wave have been attributed to specific retinal origins [8], [9]. Measured changes in timing (implicit time) or magnitude (amplitude) of these components reflect underlying changes in retinal function and have been shown to be sensitive across a range of retinal pathologies [10]–[12]. Although the conventional full-field ERG is not sensitive to early AMD [13], [14], focal ERG techniques stimulating only the central region of the retina have been shown to be sensitive to AMD [15]–[23].…”