ERG shrinks by 10% when reducing dark adaptation time to 10 min, but only for weak flashes.PURPOSE
 To compare dark-adapted (DA) ERG between 10, 15 and 20 min of dark adaptation (DA).


 In a counterbalanced random block design, 40 healthy adult subjects were dark-adapted for 10, 15 or 20 min before we recorded ERGs to nine flash strengths from 0.001 to 10.0 cd s/m2 (dilated pupils) with a DTL-like electrode.  Apart from choosing a wider range of stimulus strengths, and adding shorter DA times, the recordings fully complied with the ISCEV ERG Standard, namely using corneal electrodes, mydriasis and a standard DA sequence.


 For the b-wave amplitude, effects of reduced DA time are stronger for weaker flashes: Reducing DA from 20 to 10 min had no measurable effect on the DA 3 ERG, but reduced the DA 0.01 b-wave significantly (p < 0.0001) to 87 ± 2% (mean ± SEM).  The DA 0.001 b-wave (not part of the ISCEV ERG Standard) was more affected (down to 72 ± 4%).  Reducing dark adaptation time from 20 to 10 min in normal participants has no effect on the ISCEV DA 3 and DA 10 ERG.  The reduction in DA 0.01 ERGs to 87 ± 2% agrees with Hamilton and Graham (Doc Ophthalmol 133:11-19, 2016. https://doi.org/10.1007/s10633-016-9554-x ) who found 90 ± 2% and with Asakawa et al. (Doc Ophthalmol 139:33-44, 2019. https://doi.org/10.1007/s10633-019-09693-8 ) who found 83%. 
ERG
The DA 0.001 b-wave (not part of the ISCEV ERG Standard) was more affected (down to 72 ± 4%). 
ISCEV ERG Standard
In a counterbalanced random block design, 40 healthy adult subjects were dark-adapted for 10, 15 or 20 min before we recorded ERGs to nine flash strengths from 0.001 to 10.0 cd s/m2 (dilated pupils) with a DTL-like electrode. 
DTL-like electrode