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The photopic negative response of the macaque electroretinogram: reduction by experimental glaucoma.
Invest Ophthalmol Vis Sci. 1999 May; 40(6):1124-36.IO

Abstract

PURPOSE

To investigate the photopic flash electroretinograms (ERGs) of macaque monkeys in which visual field defects developed as a consequence of experimental glaucoma.

METHODS

Unilateral experimental glaucoma was induced in 10 monkeys by argon laser treatment of the trabecular meshwork. Visual field sensitivity was assessed behaviorally by static perimetry. Photopic ERGs were recorded to brief- (< or = 5 msec) and long-duration (200 msec) red ganzfeld flashes on a rod-suppressing blue-adapting background. Electroretinograms were recorded in four other monkeys, after intravitreal injection of tetrodotoxin (TTX; 3.8-8 p.M) to suppress action potentials of retinal ganglion and amacrine cells, and in six normal adult human subjects.

RESULTS

Experimental glaucoma removed a cornea-negative response, the photopic-negative response (PhNR), from the ERG. The PhNR in control eyes was maximal approximately 60 msec after a brief flash, 100 msec after onset, and 115 msec after offset of the long-duration stimulus. The PhNR in experimental eyes was greatly reduced when the mean deviation of the visual field sensitivity was as little as -6 dB. As visual sensitivity declined further, the PhNR was reduced only slightly more. The a- and b-waves were unchanged, even when sensitivity decreased by more than 16 dB. Tetrodotoxin also selectively reduced the PhNR. The PhNR was observed in normal human ERGs.

CONCLUSIONS

The cornea-negative PhNR of the photopic ERG depends on spiking activity and is reduced in experimental glaucoma when visual sensitivity losses are still mild. The PhNR most likely arises from retinal ganglion cells and their axons, but its slow timing raises the possibility that it could be mediated by glia. Regardless of the mechanism of its generation, the PhNR holds promise as an indicator of retinal function in early glaucomatous optic neuropathy.

Authors+Show Affiliations

College of Optometry, University of Houston, Texas 77204-6052, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

10235545

Citation

Viswanathan, S, et al. "The Photopic Negative Response of the Macaque Electroretinogram: Reduction By Experimental Glaucoma." Investigative Ophthalmology & Visual Science, vol. 40, no. 6, 1999, pp. 1124-36.
Viswanathan S, Frishman LJ, Robson JG, et al. The photopic negative response of the macaque electroretinogram: reduction by experimental glaucoma. Invest Ophthalmol Vis Sci. 1999;40(6):1124-36.
Viswanathan, S., Frishman, L. J., Robson, J. G., Harwerth, R. S., & Smith, E. L. (1999). The photopic negative response of the macaque electroretinogram: reduction by experimental glaucoma. Investigative Ophthalmology & Visual Science, 40(6), 1124-36.
Viswanathan S, et al. The Photopic Negative Response of the Macaque Electroretinogram: Reduction By Experimental Glaucoma. Invest Ophthalmol Vis Sci. 1999;40(6):1124-36. PubMed PMID: 10235545.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The photopic negative response of the macaque electroretinogram: reduction by experimental glaucoma. AU - Viswanathan,S, AU - Frishman,L J, AU - Robson,J G, AU - Harwerth,R S, AU - Smith,E L,3rd PY - 1999/5/11/pubmed PY - 2001/3/28/medline PY - 1999/5/11/entrez SP - 1124 EP - 36 JF - Investigative ophthalmology & visual science JO - Invest Ophthalmol Vis Sci VL - 40 IS - 6 N2 - PURPOSE: To investigate the photopic flash electroretinograms (ERGs) of macaque monkeys in which visual field defects developed as a consequence of experimental glaucoma. METHODS: Unilateral experimental glaucoma was induced in 10 monkeys by argon laser treatment of the trabecular meshwork. Visual field sensitivity was assessed behaviorally by static perimetry. Photopic ERGs were recorded to brief- (< or = 5 msec) and long-duration (200 msec) red ganzfeld flashes on a rod-suppressing blue-adapting background. Electroretinograms were recorded in four other monkeys, after intravitreal injection of tetrodotoxin (TTX; 3.8-8 p.M) to suppress action potentials of retinal ganglion and amacrine cells, and in six normal adult human subjects. RESULTS: Experimental glaucoma removed a cornea-negative response, the photopic-negative response (PhNR), from the ERG. The PhNR in control eyes was maximal approximately 60 msec after a brief flash, 100 msec after onset, and 115 msec after offset of the long-duration stimulus. The PhNR in experimental eyes was greatly reduced when the mean deviation of the visual field sensitivity was as little as -6 dB. As visual sensitivity declined further, the PhNR was reduced only slightly more. The a- and b-waves were unchanged, even when sensitivity decreased by more than 16 dB. Tetrodotoxin also selectively reduced the PhNR. The PhNR was observed in normal human ERGs. CONCLUSIONS: The cornea-negative PhNR of the photopic ERG depends on spiking activity and is reduced in experimental glaucoma when visual sensitivity losses are still mild. The PhNR most likely arises from retinal ganglion cells and their axons, but its slow timing raises the possibility that it could be mediated by glia. Regardless of the mechanism of its generation, the PhNR holds promise as an indicator of retinal function in early glaucomatous optic neuropathy. SN - 0146-0404 UR - https://www.unboundmedicine.com/medline/citation/10235545/The_photopic_negative_response_of_the_macaque_electroretinogram:_reduction_by_experimental_glaucoma_ L2 - https://iovs.arvojournals.org/article.aspx?volume=40&amp;issue=6&amp;page=1124 DB - PRIME DP - Unbound Medicine ER -