Although glaucoma treatment can take many forms, including medical and procedural-based approaches, one underlying principle for improving outcomes is that earlier treatment affords greater opportunity to affect better results. Consequently, there is sincere interest in discovering the earliest precursory indicators of glaucoma and ways they can be detected in the clinic.
Our current understanding of glaucoma suggests that changes in and around the retinal ganglion cells surrounding the optic nerve are some of the earliest signs of the disease. While there are several theories as to what may be the initial inciting event, the prevailing thought is that progressive loss in the ganglion cell layer eventually leads to the hallmark optic neuropathy that characterises the glaucomas.
The ability to successfully prevent deterioration of visual function associated with later glaucoma may, therefore, hinge on monitoring the viability of this crucial cell layer at an early stage of the disease.
Modern visual electrophysiology devices, such as Diopsys NOVA (Diopsys), are making this possible in clinical practice through pattern electroretinography (PERG). PERG testing, which measures an electrical signal from the retina ganglion cells in response to a stimulus, may provide clinicians actionable information regarding the viability of the ganglion cell layer.
An irregular PERG test indicates abnormal function in the ganglion cell layer that precedes cell death by months or years. In addition to early detection benefits, PERG testing also indicates response to treatment.
Unlike other standard diagnostic modalities, such as optical coherence tomography (OCT) and perimetry testing, which are useful for measuring disease progression, PERG testing can indicate functional improvements. In other words, while serial OCT and visual fields may tell you when treatment has failed, PERG can serve as an index for when treatment is working. This information is invaluable if the intent is to treat glaucoma disease parameters that do not have apparent clinical correlates.
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