 This is Jane. Jane is 75 years old and suspected to have glaucoma. Her eye pressure is elevated, but the cause could be high blood pressure. However, getting an accurate diagnosis is critical if Jane wants to avoid vision loss or even blindness. Sadly, getting an accurate diagnosis is not easy. It's a process that can require several rounds of tests before Jane's doctor can recommend a course of action. Unfortunately, Jane also suffers from cataracts, which impair image quality and make a reliable diagnosis difficult. An additional perimetry test for functional deficits produces borderline results, suggesting a possible deficit. But it is unclear whether this deficit is real or whether Jane was tired or distracted during the test. To be sure, an additional test option is the full field flash electroretinogram, or ERG. An ERG uses light to assess the function of photoreceptor, bipolar, and ganglion cells in the eye. In particular, it measures what's known as the photopic negative response. This response is specific to ganglion cells and can reflect the presence and severity of glaucoma. Historically, the test procedure has been lengthy and difficult to perform. That, combined with inconsistent results between tests, has limited the clinical use of ERG. But with the Redeval system, ERG has significantly improved. The Redeval handheld device uses skin electrodes, means no dilation, and provides color-coded test results to comfortably evaluate ERG results. To address test-retest variability, the Redeval team has recently developed a new algorithm that offers as much as five times better test-retest variability to objectively detect and monitor glaucoma patients. With little effort, Jane's Redeval measurements are done, and they suggest some abnormalities. Based on these additional findings, Jane receives a more objective diagnosis, appropriate medication, and a more informed follow-up. On her follow-up visit, Jane undergoes another ERG. Research has shown that over time, ERGs can reveal subtle changes after starting medicine to reduce intraocular eye pressure, even if no other biomarker indicates improvement. Making ERG a part of glaucoma management offers valuable information to the treatment decision process, even when media opacities are present. And with new developments, ERG looks to become an increasingly relevant and useful tool in the challenging process of diagnosing glaucoma.