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Anthony Matthew Norcia, Alexandra Yakovleva, Jeffrey L Goldberg; Contrast decrement vs increment responsiveness in glaucoma. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2448. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Recent data from mouse models of glaucoma has suggested that OFF-pathway processes are damaged before those of the ON-pathway. Here we used Steady-State Visual Evoked Potentials (SSVEPs) to determine whether ON- vs OFF-pathway biased stimuli lead to differential response patterns in human glaucoma.
Visually normal participants (51 eyes) with visual acuity correctable to 20/20 or better in each eye participated. SSVEP data from 56 eyes with varying degrees of glaucomatous visual field loss were also recorded. SSVEPs were measured in response to contrast decrements and increments to bias the responses to OFF vs ON pathways, respectively. The visual stimulus comprised a matrix of small flickering hexagonal elements (probes) superimposed on top of larger, static hexagons (pedestals) whose size was scaled according to the cortical magnification factor. The size of the central pedestal was 40 arc min, with the probes being 20% of the size of the pedestal. Sawtooth temporal waveforms with a fast decrement phase (OFF-biased) or a fast increment phase (ON-biased) were presented at a temporal frequency of 2.75 Hz. 128-channel EEG data was collected over a 0.3 to 50 Hz bandwidth. Response waveforms were extracted using a spatial filtering procedure (Dmochowski et al., NeuroImage, 2015) and waveform differences were assessed by permutation tests.
OFF-favoring sawtooth stimuli elicited evoked responses that were larger and faster than ON-biased stimuli in the normal vision participants and in patients with mean deviation scores >-5dB on Humphrey perimetry. Patients with mean deviation scores <-6 dB had nearly equal increment and decremental responses.
Consistent with data from mouse models of glaucoma, decremental sawtooth SSVEPs better distinguish visual responses in patients with different severities of glaucomatous field loss than do incremental responses.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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