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BLOG: Using ERG to be proactive as opposed to reactive in glaucoma
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The concept of “structure vs. function” is commonly discussed in glaucoma. The thinking behind it revolves around the fact that structural changes, including in the optic nerve, occur before functional ones, such as in the visual field. In this setting, it is preferred to note changes in structure early in order to avoid visually impactful losses in function. But is this truly the ideal situation? The response is “no” because even in the best of cases, there is permanent loss of tissue. Our current approach is, therefore, reactive in nature. This thought process makes the management of glaucoma difficult as providers and their patients must simply try to minimize their losses.
If we could create the ideal treatment environment, what would it look like? The best scenario is one in which no permanent damage occurs while using the least amount of intervention possible. By applying just the right amount of treatment, whether it is drops, laser or surgery, physicians minimize the risks associated with these options while maximizing the benefits. This gives the best benefit-to-risk profile, which is routinely discussed when selecting glaucoma therapy.
One method to achieve this ideal is to recognize tissue that is at risk, provide timely care and prevent permanent damage. In the treatment of glaucoma, the critical anatomy includes retinal ganglion cells (RGCs). It is these cells that are lost when glaucoma progresses, which ultimately leads to visual field loss. Electrophysiology can provide this information needed about RGCs. However, the difficulty with monitoring RGCs in the past has been the cost and time needed to evaluate them. This led to such instrumentation typically being housed only at major institutions.
The ability to perform such testing can now be done in the office through technology from Diopsys. Among the platforms that can be provided for clinicians, high-contrast pattern electroretinography (PERG) is possible to identify stressed RGCs before cell death occurs. This provides an opportunity to proactively provide timely intervention in the form of IOP reduction to rescue these at-risk cells. No longer must we wait to see green to red change on OCT, alteration of the optic nerve or decline in visual field. The strategy in how we evaluate and treat early glaucoma improves with the incorporation of this technology. As a side note, other capabilities of the Diopsys system include concentric stimulus fields that can be used in the evaluation of retinal pathology and visual evoked potentials for neurological diseases.
The advantages of this testing include:
1. PERG can be obtained much more efficiently as technical innovations have decreased the time and complexity required to perform the testing.
2. The electrode does not need be on the eye but rather uses one placed on the lower eyelid near the lid margin.
3. Interpretations can be rapid and straightforward similar to OCT using parameters of Magnitude, MagnitudeD and Mag/MagD, which incorporates a comparative database.
4. Timely information about the health of RGCs is obtained before permanent structural or functional change.
The dramatic changes in glaucoma care, such as those seen with new medication and delivery along with MIGS, have shifted our game in how to treat our patients. It is time for us to change our philosophy from defensive-minded to effectively offensive. The incorporation of PERG arms providers with the necessary tools to make these changes.
Disclosure: Teymoorian reports no relevant financial disclosures.