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Description
Paper
Summary
- compare 17 stimuli layout (C20 program) against 9 stimuli layout (R9)
- aim to examine the best stimuli for glaucoma
- lower and higher temporal frequency tests probed the same neural mechanism,
- no advantage of spatial frequency-doubling stimuli for mfVEPs
Learnings
- frequency-doubling based perimetry, generate the spatial frequency-doubling (FD) illusion. FD stimuli were hypothesised to preferentially stimulate the nonlinear Y-like cell population which, in having a very low coverage factor, are a good target for glaucoma diagnosis
- advantage of these radially scaled stimulus arrays is that, due to cortical magnification, their visual-evoked potential responses do not change over 3 or more octaves of viewing distance, meaning the same stimuli can be used to objectively test macular and peripheral fields
- frequency-doubling technology (FDT) and Matrix perimeters have been a relatively successful addition to our tools for managing glaucoma, with reports of earlier detection [1], and better correlation with nerve fibre loss [2]. recent studies suggest that FD-based perimetry does not perform very differently to other standard methods [3, 4]
- For the purposes of the mfVEPs, the stimulus frequencies were incommensurate, and so none of the stimuli, their harmonics or their intermodulation frequencies overlapped in the discrete Fourier transform of the VEP record. To insure this, the stimuli had exactly: 144, 148, 153, 159, 166, 176, 190, 202 or 210 cycles in the 20.18 s of each VEP recording. Thus, the frequency resolution, df, was 1/20.18 Hz and therefore, the stimulus frequencies ran from 7.14 and 10.4 Hz.