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DavidKeating - 20 Oct 2008
Module 34 - Photopic Negative Response
To be completed by (Frishman)
1. Scope
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For light adapted conditions
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2. Identification
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2.1. Number
| 34 |
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2.2. Version number
| 1.0 |
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2.3. Date of approval
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3. Protocol use(s)
Assessment Cone-driven photopic negative responses
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4. Patient population
Patients with glaucoma and other diseases that affect inner retinal functions, and/or cause optic neuropathy
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5. Technical issues
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4.1. Equipment and facilities
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See ISCEV Standard (2008 update) and Protocols general aspects. An LED-based ganzfeld or focal stimulator that produces chromatic test stimuli and background levels is preferable, but not essential
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4.2. Staff expertise and responsibilities
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No specific definition, unless focal stimuli are used - see ISCEV Standard (2008 update) and Protocols general aspects.
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4.3. Procedure
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No specific definition, see ISCEV Standard (2008 update) and Protocols general aspects.
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4.4. Patient Information
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No specific definition, see ISCEV Standard (2008 update) and Protocols general aspects.
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6. Response evaluation (with example) Amplitude and latency of b-wave and
PhNR 7. Reporting and storage Curves and amplitudes. 8. Calibration No specific definition, see ISCEV Standard (2008 update) and Protocols general aspects. 9. Protocol Specifications
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Description
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Averages per step
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Adaptation time
| At least 10 min, as for any light adapted flash ERG |
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Acquisition
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Sample frequency
| At least 1 KHz |
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Sweep pre-trigger time
| 20 ms |
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Sweep post-trigger time
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Sweeps per result
| At least 10 |
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Interstimulus interval
| One second |
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Drift removal
| yes |
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Manual rejection of sweeps
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DC off-set removal
| Zero at the beginning of each sweep |
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Stimulus
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Brief flash full field ERG (but see ref 6 for focal stimulation)
Narrow band spectral stimuli are best that preferentially stimuli one cone type. L-cone stimulation is most practical with commercially available LED based stimuli
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Pulse frequency
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Pulse duration (d)
| Brief flash, less than 5 msec |
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Stimulus luminance
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Red: 4 steps of doubling strength up to 2.5 to 3.0 cd.s.m^2
White: stronger stimuli are needed than for red stmuli - at least 3.0 cd.s.m^2
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Stimulus color
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Red is preferable: narrow band LED with Lmax: 630 to 660 nm
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Background luminance
| 100 scotopic cd.m^2 |
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Background color
| Blue is preferable is stimulus is red: narrow band, LED with Lmax 450 to 470 nm |
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Channels (1 and 2)
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Filter low frequency cutoff
| 0.1 Hz if possible, no greater than 1 Hz |
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Filter high frequencycutoff
| 300 Hz |
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Y-axis scaling
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10. Relevant References
- 1. Rangaswamy NV, Shirato S, Kaneko, M, Digby, B, Robson JG, Frishman LJ. Effects of spectral characteristics of ganzfeld stimuli on the photopic negative response (PhNR) of the ERG. Invest Ophthalmol Vis Sci. 2007;48:4818-4828.
- 2. Viswanathan S, Frishman LJ, Robson JG, Walters, JW. The photopic negative response of the flash electroretinogram in primary open angle glaucoma. Invest Ophthalmol Vis Sci. 2001; 42:514-522.
- 3. Sustar M, Cvenkel B, Brecelj J. The effect of broadband and monochromatic stimuli on the photopic negative response of the electroretinogram in normal subjects and in open-angle glaucoma patients. Doc Ophthalmol. 2009; 118: 167-177.
- 4. Machida S , Gotoh Y, Toba Y, Ohtaki A, Kaneko M, Kurosaka D. Correlation between photopic negative response and retinal nerve fiber layer thickness and o ptic disc topog raphy in glaucomatous eyes. Invest Ophthalmol Vis Sci. 2008 ; 49: 2201-2207.
- 5. (Focal PhNR): Machida S, Toba Y, Ohtaki A, Gotoh Y, Kaneko M, Kurosaka D. Photopic negative response of focal electoretinograms in glaucomatous eyes. Invest Ophthalmol Vis Sci. 2008;49: 5636-5644.
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