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Fulltext Photopic and scotopic multifocal pupillographic responses in age-related macular degeneration

Rosli Y, Bedford SM, James AC, Maddess T

Vision Res, 2012 Sep 15;69:42-8.
PMID: 22898702 DOI: 10.1016/j.visres.2012.07.019

We compared photopic and scotopic multifocal pupillographic stimuli in age-related macular degeneration (AMD). Both eyes of 18 normal and 14 AMD subjects were tested with four stimulus variants presented at photopic and 126 times lower luminances. The multifocal stimuli presented 24 test regions/eye to the central 60°. The stimulus variants had two different check sizes, and when presented either flickered (15 Hz) for 266 ms, or were steady for 133 ms. Mean differences from normal of 5 to 7 dB were observed in the central visual field for both photopic and scotopic stimuli (all p < 0.00002). The best areas under receiver operating characteristic plots for exudative AMD in the photopic and scotopic conditions were 92.9 ± 8.0 and 90.3 ± 5.7% respectively, and in less severely affected eyes 83.8 ± 9.7% and 76.9 ± 8.2%. Damage recorded at photopic levels was possibly more diffusely distributed across the visual field. Sensitivity and specificity was similar at photopic and scotopic levels.
Low-spatial-frequency channels and the spatial frequency-doubling illusion

Rosli Y, Bedford SM, Maddess T

Invest Ophthalmol Vis Sci, 2009 Apr;50(4):1956-63.
PMID: 18469194 DOI: 10.1167/iovs.08-1810

This study examined the number and nature of spatiotemporal channels in the region where the frequency-doubling (FD) illusion would be expected to occur at eight locations spanning the central 30 degrees of the visual field.
Multifocal frequency-doubling pattern visual evoked responses to dichoptic stimulation

Rosli Y, Maddess T, Dawel A, James AC

Clin Neurophysiol, 2009 Dec;120(12):2100-2108.
PMID: 19846337 DOI: 10.1016/j.clinph.2009.09.006

OBJECTIVE: To examine the feasibility of a multifocal visual evoked potential (mfVEP) binocularly, using a variant of the multifocal frequency-doubling (FD) pattern-electroretinogram (MFP).
METHODS: Stimuli were presented in both monocular and dichoptic conditions at eight visual field locations/eye. The incommensurate stimulus frequencies ranged from 15.45 to 21.51 Hz. Five stimulus conditions differing in spatial frequency and orientation were examined for three viewing conditions. The resulting 15 stimulus conditions were examined in 16 normal subjects who repeated all conditions twice.
RESULTS: Several significant independent effects were identified. Response amplitudes were reduced for dichoptic viewing (by 0.85 times, p<4 x 10(-11)); offset by increases in responses for between eye differences of one octave of spatial frequency: lower (1.15 times, 0.1 cpd); higher (1.29 times, 0.4 cpd), both p<1.8 x 10(-7). Crossed orientations produced significant effects upon response phase (p=0.023) but not amplitude (p=0.062).
CONCLUSIONS: The results indicated that dichoptic evoked potentials using multifocal frequency-doubling illusion stimuli are practical. The use of crossed orientation, or differing spatial frequencies, in the two eyes reduced binocular interactions.
SIGNIFICANCE: The results indicate a method wherein several spatial or temporal and frequencies per visual field region can be tested in reasonable time using a multifocal VEP using spatial frequency-doubling stimuli.
Fulltext Localization of Neuronal Gain Control in the Pupillary Response

Carle CF, James AC, Rosli Y, Maddess T

Front Neurol, 2019;10:203.
PMID: 30930833 DOI: 10.3389/fneur.2019.00203

Multifocal pupillographic objective perimetry (mfPOP) is being developed as an alternative to standard visual perimetry. In mfPOP, pupil responses to sparse multifocal luminance stimuli are extracted from the overall composite response. These individual test-region responses are subject to gain-control which is dependent on the temporal and spatial density of stimuli. This study aimed to localize this gain within the pupil pathway. Pupil constriction amplitudes of 8 subjects (41.5 ±12.7 y, 4 male) were measured using a series of 14 mfPOP stimulus variants. The temporal density of stimulus signal at the levels of retina, pretectal olivary nuclei (PON), and Edinger-Westphal nuclei (EWN) were controlled using a combination of manipulation of the mean interval between stimulus presentations (3 or 6 stimuli/s/hemiretina) and the restriction of stimuli to specific subsets of the 24 visual field test-regions per eye (left or right eye, left or right hemifield, or nasal or temporal hemifield). No significant difference was observed between mfPOP variants with differing signal density at the retina or PON but matched density at the other levels. In contrast, where signal density differed at the EWN but was the same at the retinal and PON levels e.g., between 3 stim/s homonymous hemifield and all test-region variants, significant reductions in constriction amplitudes were observed [t(30) = -2.07 to -2.50, all p < 0.05]. Similar, although more variable, relationships were seen using nasal, and temporal hemifield stimuli. Results suggest that the majority of gain-control in the subcortical pupillary pathway occurs at the level of the EWN.
Insights for mfVEPs from perimetry using large spatial frequency-doubling and near frequency-doubling stimuli in glaucoma

Abdullah SN, Sanderson GF, Husni MA, Maddess T

Documenta ophthalmologica. Advances in ophthalmology, 2020 08;141(1):45-55.
PMID: 32034583 DOI: 10.1007/s10633-020-09750-7

PURPOSE: To compare two forms of perimetry that use large contrast-modulated grating stimuli in terms of: their relative diagnostic power, their independent diagnostic information about glaucoma and their utility for mfVEPs. We evaluated a contrast-threshold mfVEP in normal controls using the same stimuli as one of the tests.
METHODS: We measured psychophysical contrast thresholds in one eye of 16 control subjects and 19 patients aged 67.8 ± 5.65 and 71.9 ± 7.15, respectively, (mean ± SD). Patients ranged in disease severity from suspects to severe glaucoma. We used the 17-region FDT-perimeter C20-threshold program and a custom 9-region test (R9) with similar visual field coverage. The R9 stimuli scaled their spatial frequencies with eccentricity and were modulated at lower temporal frequencies than C20 and thus did not display a clear spatial frequency-doubling (FD) appearance. Based on the overlapping areas of the stimuli, we transformed the C20 results to 9 measures for direct comparison with R9. We also compared mfVEP-based and psychophysical contrast thresholds in 26 younger (26.6 ± 7.3 y, mean ± SD) and 20 older normal control subjects (66.5 ± 7.3 y) control subjects using the R9 stimuli.
RESULTS: The best intraclass correlations between R9/C20 thresholds were for the central and outer regions: 0.82 ± 0.05 (mean ± SD, p ≤ 0.0001). The areas under receiver operator characteristic plots for C20 and R9 were as high as 0.99 ± 0.012 (mean ± SE). Canonical correlation analysis (CCA) showed significant correlation (r = 0.638, p = 0.029) with 1 dimension of the C20 and R9 data, suggesting that the lower and higher temporal frequency tests probed the same neural mechanism(s). Low signal quality made the contrast-threshold mfVEPs non-viable. The resulting mfVEP thresholds were limited by noise to artificially high contrasts, which unlike the psychophysical versions, were not correlated with age.
CONCLUSION: The lower temporal frequency R9 stimuli had similar diagnostic power to the FDT-C20 stimuli. CCA indicated the both stimuli drove similar neural mechanisms, possibly suggesting no advantage of FD stimuli for mfVEPs. Given that the contrast-threshold mfVEPs were non-viable, we used the present and published results to make recommendations for future mfVEP tests.
Fulltext Retinotopic effects of visual attention revealed by dichoptic multifocal pupillography

Rosli Y, Carle CF, Ho Y, James AC, Kolic M, Rohan EMF, et al.

Sci Rep, 2018 02 14;8(1):2991.
PMID: 29445236 DOI: 10.1038/s41598-018-21196-1

Multifocal pupillographic objective perimetry (mfPOP) has recently been shown to be able to measure cortical function. Here we assessed 44 regions of the central 60 degrees of the visual fields of each eye concurrently in 7 minutes/test. We examined how foveally- and peripherally-directed attention changed response sensitivity and delay across the 44 visual field locations/eye. Four experiments were completed comparing white, yellow and blue stimulus arrays. Experiments 1 to 4 tested 16, 23, 9 and 6 subjects, 49/54 being unique. Experiment 1, Experiments 2 and 3, and Experiment 4 used three variants of the mfPOP method that provided increasingly improved signal quality. Experiments 1 to 3 examined centrally directed attention, and Experiment 4 compared effects of attention directed to different peripheral targets. Attention reduced the sensitivity of the peripheral locations in Experiment 1, but only for the white stimuli not yellow. Experiment 2 confirmed that result. Experiment 3 showed that blue stimuli behaved like white. Peripheral attention showed increased sensitivity around the attentional targets. The results are discussed in terms of the cortical inputs to the pupillary system. The results agree with those from multifocal and other fMRI and VEP studies. mfPOP may be a useful adjunct to those methods.