Novel electrophysiological instrument for rapid and objective assessment of magnocellular deficits associated with glaucoma

Vance Zemon, James C. Tsai, Max Forbes, Lama A. Al-Aswad, Chi Ming Chen, James Gordon, Vivienne C. Greenstein, George Hu, Evy C. Strugstad, Elona Dhrami-Gavazi, Lawrence F. Jindra

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Purpose: To introduce a rapid and objective electrophysiological technique that can assess visual function in the magnocellular pathway, which is thought to be affected in early-stage glaucoma. Methods: Low-contrast bright or dark isolated-checks were luminance-modulated against a static background at 10 Hz in order to drive preferentially the magnocellular ON or OFF pathway. Visual evoked potentials were recorded during 1-s epochs of stimulation and responses at the stimulus frequency were measured. Artifact rejection features ensured that eight valid runs were obtained per eye. Signal-to-noise ratios (SNR) were derived based on a multivariate statistic. In order to demonstrate its functionality, a small group of patients with glaucoma (N = 18, Snellen acuity of 20/30 or better) and control observers (N = 16) were tested. A participant failed the test if either eye yielded an SNR ≤ 1. Receiver-operating-characteristic curve analysis was used to estimate the accuracy of group classification. Results: The instrument was found to elicit reliable responses from control observers. For the 15% bright condition, all control observers yielded significant isolated-check VEPs (icVEPs), whereas the majority of patients failed to do so, indicating significant losses in central visual function. This condition produced the highest classification accuracy (94%), followed by the 10% dark condition (91%). Conclusions: Both ON and OFF divisions of the magnocellular pathway can be assessed rapidly through the application of the icVEP technique. This measure of central visual function may be of value in the detection of glaucomatous deficits and may complement tests of peripheral function.

Original languageEnglish
Pages (from-to)233-243
Number of pages11
JournalDocumenta Ophthalmologica
Issue number3
StatePublished - Nov 2008
Externally publishedYes


  • Glaucoma
  • Magnocellular pathway
  • ON and OFF pathways
  • Visual evoked potentials


Dive into the research topics of 'Novel electrophysiological instrument for rapid and objective assessment of magnocellular deficits associated with glaucoma'. Together they form a unique fingerprint.

Cite this