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Posted on Thursday August 27, 2020

Summary of select, peer reviewed published research on glaucoma:

Glaucoma is a group of conditions characterized by cupping of the optic disc with corresponding visual field defects due to retinal ganglion cell (RGC) loss. In some cases, the condition can progress to the point of causing optic neuropathy. It is the most common cause of irreversible blindness worldwide and because it is a progressive condition, early detection is necessary in order to minimize potential vision loss.

One way of detecting glaucoma before permanent vision loss is the use of electrophysiology tests. These tests are particularly important, as research has found that visual field defects do not become noticeable until 25% to 35% of the RGCs have been lost. ISCEV standard tests for detecting RGC function are pattern ERG (PERG) and photopic negative response (PhNR).

Both PERG and PhNR excel at detecting glaucoma in its early stages and have done so for several decades, PERG for almost 40 years and PHNR for 20 years. Diagnosys has worked with the researchers who discovered the PhNR protocol (red flash on a blue background) for well over a decade in order to refine and enhance this test’s capabilities. While both tests measure RGC function, PhNR also measures cones and bipolar cell function. ISCEV guidelines requires near optimal correction for PERG and full dilation for PhNR.



Arden GB, Vaegan, Hogg CR. Clinical and Experimental Evidence that the Pattern Electroretinogram (PERG) is Generated in more Proximal Retinal Layers than the Focal Electroretinogram (FERG). Ann NY Acad Sci 1982; 388:580-601.

Banitt MR, Ventura LM, Feuer WJ, et al. Progressive Loss of Retinal Ganglion Cell Function Precedes Structural Loss by Several Years in Glaucoma Suspects. Invest Ophthalmol Vis Sci. 2013;54:2346–2352.

Berninger TA, Arden GB. The Pattern Electroretinogram. Eye 1988 (2) Suppl S257-S283.

Bode SFN, Jehle T, Bach M. Pattern Electroretinogram in Glaucoma Suspects: New Findings from a Longitudinal Study. Invest Ophthalmol Vis Sci. 2011;52:4300–4306.

Kerrigan-Baumrind LA, Quigley HA, Pease ME, et al. Number of Ganglion Cells in Glaucoma Eyes Compared with Threshold Visual Field Tests in the Same Persons. Invest Ophthalmol Vis Sci. 2000;41:741–748.

Niyadurupola N, Luu CD, Nguyen DQ, et al. Intraocular Pressure Lowering is Associated with an Increase in the Photopic Negative Response (PhNR) Amplitude in Glaucoma and Ocular Hypertensive Eyes. Invest Ophthalmol Vis Sci.2013;54:1913–1919.

North RV, Jones AL, Drasdo N, et al. Electrophysiological Evidence of Early Functional Damage in Glaucoma and Ocular Hypertension. Invest Ophthalmol Vis Sci. 2010;51:1216–1222.

Preiser D, Lagrèze WA, Bach M, et al. Photopic Negative Response versus Pattern Electroretinogram in Early Glaucoma. Invest Ophthalmol Vis Sci. 2013;54:1182–1191.

Robson AG, Nilsson J, Li S, et al. ISCEV Guide to Visual Electrodiagnostic Procedures. Springer 2018;136:1-26. Viswanathan S, Frishman LJ, Robson JG, et al. The Photopic Negative Response of the Flash Electroretinogram in Primary Open Angle Glaucoma. Invest Ophthalmol Vis Sci. 2001;42:514–522.

Weinstein GW, Arden GB, Hitchings RA, et al. The Pattern Electroretinogram (PERG) in Ocular Hypertension and Glaucoma. Arch Ophthalmol 1988;106:923-928.