Rod b-wave series

1. Scope and uses

For dark-adapted conditions, covering most indications of screening in Rod pathway alterations. Detection of diffuse dysfunction in the rod pathway; Assessment of rod phototransduction dynamics; Screen for retinal toxicity of scotopic system;

2. Identification

Number 11; Version number 1.0.2.4.

3. Patient population

Genetic rod-cone degenerations Patients exposed to substances that might have retinal toxic effects.

4. Technical issues

Equipment and facilities, Staff expertise and responsibilities, Procedure, Patient Information: No specific definition, see ISCEV Standard (2008 update) and Protocols general aspects.

5. Response evaluation

A model is be fitted for the interrelation between b-wave amplitude and luminance, to determine 4 parameters: Vmax1, k1, Vmax2 and k2.

6. Reporting

Curves, amplitudes, latencies and parameters must be reported.

7. Calibration

No specific definition, see ISCEV Standard (2008 update) and Protocols general aspects.

8. Protocol Specifications

9.1. Common parameters for all steps

Aquisition

1. DC off-set removal On: 20 (ms);
2. Drift removal: Off;
3. Sample frequency: 1000 (Hz);
4. Filter high frequency cutoff: 300 (Hz);
5. Filter low frequency cutoff: 0.3 (Hz);
6. Manual rejection of sweeps: On;
7. Sweep pre-trigger time: 20 (ms);

Stimuli

1. Flash duration: 1 (ms);
2. Stimulus color: White 6500;

9.2. Steps

10. Relevant Reference

Evans LS, Peachey NS, Marchese AL. Comparison of three methods of estimating the parameters of the Naka-Rushton equation.Doc Ophthalmol 1993;84:19-30.

Peachey NS, Alexander KR, Fishman GA. The luminance-response function of the dark-adapted human electroretinogram. Vision Res 1989;29:263-270.

Moskowitz A, Hansen RM, Akula JD, Eklund SE, Fulton AB. Rod and rod-driven function in achromatopsia and blue cone monochromatism. Invest Ophthalmol Vis Sci 2009;50:950-958.

11. Example: model fitting

Back to Rod b-wave series

Comments on Rod b-wave series

-- DavidKeating - 20 Oct 2008

As the scotopic series is specified using photopic luminance there needs also to be a specification of the spectral composition of the light and of the photopic/scotopic ratio to achieve comparable results between laboratories.

John RObson is currently chairing the Committee of ISCEV TEchnical Guidelines (update of the ISCEV calibration guidelines) and has suggested a photopic: scotopic ratio 2.52 based on a colour temperature of 7000°K. Extended protocols should co-ordinate with the work of John's committee.

-- DaphneMcCulloch - 30 Apr 2009

Is there any reason for a "RodBwaveseries" AND a "RodVlogI" module? I think we can exclude one. My suggestion is to keep the "RodVLogI".

-- AndreMessias - 12 May 2009

Of course there is a scotopic B-wave series and a scotopic a-wave series that are the same as what is often called the "Rod V logI" for the b- and a-waves respectively. I prefer 'scotopic' in the name as the responses are initiated by rods but actually generated by the bipolar and other cells. Also, 'V logI' is not understood by non-experts and can be confusing as it refers as to b-wave amplitude ('V') versus the time-integrated luminance of a flash stimulus ('I'). It also encourages the common error of referring to the extended light flash as 'intensity', the photometric term that applies to point sources.

-- DaphneMcCulloch - 12 Jun 2009

I agree that there is a "b-Wave Series" and a "a-Wave Series", but my question was about the existence of a protocol number 11 (Rod b-wave series) AND a protocol number 12 (Rod b-wave VlogI? ) additionally to the number 13 (a-wave analysis). I also agree with you about the name “VLogI”, so we could have a protocol number 11 called Scotopic b-Wave Series, AND a protocol number 13 called Scotopic a-Wave Series, and remove the protocol number 12.

-- AndreMessias - 18 Jun 2009

The model fitting: (1) this seems to be the sum of two Hill functions with the Hill coefficient set to one, right? It fits rather well to my own data. However, (2) the saturation levels V2 is given incorrectly on the axis: when we accept the definition from the formula, then what is depicted on the axis is (V1+V2)

-- MichaelBach - 15 Jul 2009