Abstract
Purpose: :
To investigate the zeroth order kernel (K0) of multifocal electroretinogram (mfERG). K0 represents the raw data signal to be cross-correlated with the stimulus sequence in the process of extracting mfERGs.
Methods: :
K0s were analyzed in more than 200 recordings of mfERG obtained from healthy eyes and various pathologies using VERIS 5.1.12 (EDI Inc., San Mateo, CA).
Results: :
K0 has a steady waveform fully synchronized with the base rate (BR) of the stimuli. The amplitude of K0 has a drastic inverse-correlation with the BR, e.g. 0.4-2.0 microV with 75 Hz BR can amplify up to 100-fold with 18.75 Hz BR. The amplitude of K0 also depends on the total luminous intensity of the stimulus and the pupil size to a much greater extent than that of the first order kernel (K1) of mfERG does. With the same BR, K0 amplitude generally correlates with K1 amplitude, however eyes with an advanced cataract show smaller K1 in the center with larger K0 probably due to the greater stray light effects in K0.
Conclusions: :
K0 of mfERG develops properties of flicker ERGs in the posterior part of the fundus. While the deficit of the multifocal distribution may limit the clinical utility, K0 is a resource of unique information of mfERG. K0 amplitude relative to K1 can be used as an index of the stray light effects. In case with non-dilated pupil, the retinal illuminance may also be estimated by the amplitude of K0.
Keywords: electroretinography: clinical