Abstract
Purpose: :
To estimate responses to multiple flashes from an m-sequence of the flash ERG, and demonstrate a technique that provides information equivalent to multiple tests from a single brief record.
Methods: :
The flash ERG was recorded with normal subjects using an m-sequence stimulus under scotopic and photopic conditions. The flash intensities used were 0.002 cd•s/m2 and 6 cd•s/m2 respectively. The corresponding base intervals of the m-sequence stimulation were 125 ms and 10 ms. From the response to an m-sequence cycle we derived the complete binary kernel series. We retained only the terms that exceed the noise level, and transformed them into the single flash response for the scotopic condition and into a series of double flash responses for the photopic condition with an increasing inter-stimulus interval. We estimated the contribution of the second flash in each double flash response by subtracting the contribution of the first flash as a single flash response. The amplitude of the remaining signal was plotted against the inter-stimulus interval as a recovery curve after adaptation to the initial test flash.
Results: :
In both scotopic and photopic conditions, the time course of response recovery rate was linear followed by saturation. In the photopic condition, complete recovery to the isolated single flash response was reached after approximately 35 ms. Under the scotopic condition, complete recovery was reached after 600 ms.
Conclusions: :
This new method reveals information regarding the retinal response dynamics that was formerly not accessible with means feasible in a clinical setting, because multiple tests were required with different inter-stimulus intervals. The clinical importance of these adaptation recovery plots is yet to be determined.
Keywords: electroretinography: non-clinical • electroretinography: clinical • retina