Abstract | PURPOSE: METHODS: Photopic flash ERGs were recorded differentially, with DTL electrodes, between the two eyes of 22 patients with diagnosed optic neuropathy (n = 17, anterior ischemic optic neuropathy [AION]; n = 5, compressive optic neuropathy) and 25 age-matched control subjects and in 17 eyes of 13 monkeys (Macaca mulatta). The stimulus consisted of brief (<5 ms) red (lambda(max) = 660 nm) Ganzfeld flashes (energy range, 0.5-2.0 log td-s) delivered on a rod-saturating blue background of 3.7 log sc td (lambda(max) = 460 nm). An eye of the patient with ischemic changes at the disc was classified as symptomatic if it showed visual field defects with a mean deviation (MD) of P < 2%. Recordings in macaque monkeys were made before and after inner retinal blockade with tetrodotoxin (TTX) (1.2-2.1 microM; n = 7), TTX+N-methyl- d-aspartate ( NMDA; 1.4-6.4 mM; n = 7), and cis-2, 3 piperidine dicarboxylic acid (PDA; 3.3-3.8 mM; n = 3). RESULTS: The PhNR amplitude was significantly reduced in both symptomatic (P = 3.4 x 10(-8)) and asymptomatic (P = 0.036) eyes of patients with AION or compressive optic neuropathy (P = 0.0054) compared with control subjects. The PhNR amplitude in the symptomatic eye showed a moderate correlation with field defects (P < 0.05) similar to previous findings in open-angle glaucoma. The a-wave also was reduced significantly in the symptomatic eye (P = 0.0002) of patients with AION. The i-wave, a positive wave on the trailing edge of the b-wave peaking around 50 ms, became more prominent in eyes in which the PhNR was significantly reduced. In monkeys, the PhNR was eliminated by TTX. The a-wave at the peak and later times was reduced by TTX, further reduced by NMDA, and eliminated after PDA in response to the red stimuli. PDA also eliminated the i-wave. CONCLUSIONS: PhNR amplitude is significantly reduced in eyes with open-angle glaucoma, AION, and compressive optic neuropathy. Experiments in primates indicate that this reduction reflects loss of a spike-driven contribution to the photopic ERG. There also are small spike-driven contributions to the a-wave elicited by full-field red stimuli. The i-wave, which becomes more prominent when the PhNR is reduced, has origins in the off-pathway distal to the ganglion cells.
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Authors | Nalini V Rangaswamy, Laura J Frishman, E Ulysses Dorotheo, Jade S Schiffman, Hasan M Bahrani, Rosa A Tang |
Journal | Investigative ophthalmology & visual science
(Invest Ophthalmol Vis Sci)
Vol. 45
Issue 10
Pg. 3827-37
(Oct 2004)
ISSN: 0146-0404 [Print] United States |
PMID | 15452095
(Publication Type: Comparative Study, Journal Article, Research Support, U.S. Gov't, P.H.S.)
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Chemical References |
- Pipecolic Acids
- Tetrodotoxin
- 2,3-piperidinedicarboxylic acid
- N-Methylaspartate
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Topics |
- Adult
- Aged
- Animals
- Electroretinography
- Female
- Glaucoma, Open-Angle
(physiopathology)
- Humans
- Light
- Macaca mulatta
- Male
- Middle Aged
- N-Methylaspartate
(pharmacology)
- Nerve Compression Syndromes
(physiopathology)
- Optic Nerve Diseases
(physiopathology)
- Optic Neuropathy, Ischemic
(physiopathology)
- Photic Stimulation
- Pipecolic Acids
(pharmacology)
- Retina
(drug effects, physiopathology)
- Tetrodotoxin
(pharmacology)
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