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DavidKeating - 20 Oct 2008
13. a-wave analysis
Module 13 - a-wave analysis To be completed by (Mitch Brigell) 1. Scope
| For dark-adapted conditions, defects in outer segments dynamics |
2. Identification
| 2.1. Number | 13 |
| 2.2. Version number | 1.0 |
| 2.3. Date of approval | |
3. Protocol use(s)
Detection of diffuse dysfunction in the rod photoreceptors; Assessment of rod phototransduction dynamics; Screen for retinal toxicity of scotopic system; |
4. Patient population
Rod-cone degeneration Patients exposed to substances that might have retinal toxic effects |
5. Technical issues
| 4.1. Equipment and facilities | Equipment must have the capability of producing bright flashes needed for this protocol. Analysis algorithm must be implemented |
| 4.2. Staff expertise and responsibilities | No specific definition, see ISCEV Standard (2008 update) and Protocols general aspects. |
| 4.3. Procedure | No specific definition, see ISCEV Standard (2008 update) and Protocols general aspects. |
| 4.4. Patient Information | No specific definition, see ISCEV Standard (2008 update) and Protocols general aspects. |
6. Response evaluation (with example)
A model must be fit to the leading edges (in the time interval between 10% and 80% of peak amplitude as illustrated in the figure) of the dark-adapted a-wave.
P3(I,t) = {1 - exp[-I. S. (t - td)
2]} ·
Rmp3
for t>td (1)
where the amplitude names P3, named after Granit's receptoral component, is a function of flash energy I and time t after the occurrence of a brief flash. S is a sensitivity parameter that scales I(flash energy);
Rm is the maximum amplitude; and td is a brief delay.
7. Reporting and storage Waveforms,
Rm and S parameters must be reported.
8. Calibration
No specific definition, see ISCEV Standard (2008 update) and Protocols general aspects.
9. Protocol Specifications Description | 1. Dark adapted 1 cd .s/m2 | 2. Dark adapted 3 cd .s/m2 | 3. Dark adapted 10 cd .s/m2 | 4. Dark adapted 30 cd .s/m2 | 5. Dark adapted 100 cd .s/m2 |
| Acquisition | | | | | |
| Sample Frequency | 1000 (Hz) | 1000 (Hz) | 1000 (Hz) | 1000 (Hz) | 1000 (Hz) |
| Sweep pre-trigger time | 20 (ms) | 20 (ms) | 20 (ms) | 20 (ms) | 20 (ms) |
| Sweep post-trigger time | 100 (ms) | 100 (ms) | 100 (ms) | 100 (ms) | 100 (ms) |
| Sweeps per result | 2 | 2 | 2 | 2 | 2 |
| Interstimulus interval | 60 (s) | 60 (s) | 60 (s) | 60 (s) | 60 (s) |
| Drift removal | Off | Off | Off | Off | Off |
| Manual rejection of sweeps | Off | Off | Off | Off | Off |
| DC off-set removal | On: 20 (ms) | On: 20 (ms) | On: 20 (ms) | On: 20 (ms) | On: 20 (ms) |
| Stimulus | | | | | |
| Pulse duration (d) | 1 ms | 1 ms | 1 ms | 1 ms | 1 ms |
| Stimulus luminance | 1 cd .s/m2 | 3 cd .s/m2 | 10 cd .s/m2 | 30 cd .s/m2 | 100 cd .s/m2 |
| Stimulus color | White 6500K | White 6500K | White 6500K | White 6500K | White 6500K |
| Background luminance | 0 cd/m2 | 0 cd/m2 | 0 cd/m2 | 0 cd/m2 | 0 cd/m2 |
| Background color | White 6500K | White 6500K | White 6500K | White 6500K | White 6500K |
| Channels (1 and 2) | | | | | |
| Filter low frequency cutoff | 0.3 (Hz) | 0.3 (Hz) | 0.3 (Hz) | 0.3 (Hz) | 0.3 (Hz) |
| Filter high frequency cutoff | 300 (Hz) | 300 (Hz) | 300 (Hz) | 300 (Hz) | 300 (Hz) |
| Y-axis scaling | 50 (uV) | 50 (uV) | 50 (uV) | 50 (uV) | 50 (uV) |
- a_wave.jpg:
jpg 
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