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B. Falsini, A. Fadda, A. Di Renzo, D. Marangoni, V. Parisi, G. Stifano, E. Balestrazzi, C. E. Riva; Short-Term Enhancement of Light-Adapted Electroretinogram During Sustained Flicker Stimulation in Normal Subjects: Implications for Neurovascular Coupling. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5812.
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Flicker stimulation induces changes in retinal activity and metabolism that are coupled with an increase in blood flow. This neurovascular coupling underlies a retinal autoregulation process, linking neural activity to its energy source. Based on this model, the authors evaluated whether light-adapted electroretinogram (ERG) undergoes in normal subjects short-term, autoregulatory changes during sustained flicker stimulation (SFS)
In 14 normal volunteers, ERGs were recorded from the macular region (18°) in response to an 8 Hz sine-wave flicker stimulus, continuously presented over 6 minutes after 20 minutes of light adaptation to an equiluminant unmodulated field. One stimulus temporal period (125 ms) was sampled and averaged in packets (n = 20) of 60 sweeps each (about 16 seconds). Amplitudes and phases of the response 1st and 2nd harmonics (1F and 2F, respectively) were measured and plotted as a function of recording time.
Forty-eight (± 16) seconds after the SFS onset, ERG 2F showed, on average, an increase in amplitude (about 25% from baseline, p < 0.05), followed by a plateau at 160-240 seconds and a progressive decrease to baseline level at 240-320 seconds of SFS. The 1F showed a similar trend, although not significant. Response phase of both components was stable throughout SFS.
Light-adapted ERG shows in normal subjects a short-term enhancement during SFS, suggesting autoregulatory changes linked to flicker-induced hyperemic response. This may have implications for detecting retinal diseases (e.g. diabetic retinopathy, glaucoma) with a supposedly disrupted neurovascular coupling.
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