Early screening opportunities for glaucoma
As glaucoma progresses, it can cause optic neuropathy, making it the leading cause of irreversible blindness worldwide. Since the disease is progressive, early detection is crucial for minimizing vision loss and preserving quality of life.
One of the challenges with glaucoma is that visual field defects often go unnoticed until a significant portion (25% to 35%) of the retinal ganglion cells have already been lost. By the time vision issues become apparent, considerable and irreversible damage may have occurred. This is why early testing is critical.
Visual electrophysiology for glaucoma
To detect glaucoma before vision loss becomes permanent, electrophysiology tests, specifically Pattern Electroretinogram (PERG) and Photopic Negative Response (PhNR), are essential. Both of these tests are recognized by the International Society for Clinical Electrophysiology of Vision (ISCEV) as effective tools for assessing retinal ganglion cell (RGC) function:
Pattern Electroretinogram (PERG): This test has been used for nearly 40 years to assess RGC function and is highly effective in identifying early-stage glaucoma. It requires near-optimal vision correction to ensure accurate results.
Photopic Negative Response (PhNR): With over 20 years of clinical use, PhNR measures not only RGC function but also the functionality of cones and bipolar cells in the retina. The red flash on a blue background protocol for PhNR has been refined over the years to enhance its diagnostic capabilities.
References
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Prencipe M, Perossini T, Brancoli G, Perossini M. The photopic negative response (PhNR): measurement approaches and utility in glaucoma. Int Ophthalmol. 2020 Dec;40(12):3565-3576. doi: 10.1007/s10792-020-01515-0. Epub 2020 Jul 31. PMID: 32737731; PMCID: PMC7669808.