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Purpose: Multifocal pupillographic objective perimetry (mfPOP) is being developed as an alternative to subjective threshold perimetry for the management of visual and neurological disorders. Here, we evaluate, in normal subjects, differences in signal quality between the original mfPOP method of spatially sparse Continuous stimulus presentation and the new Clustered Volleys (CVs) method. We hypothesized that the CVs method would lead to increased signal-to-noise ratios (SNRs) over the original method due to the stabilization of gain within the pupillary system., Methods: Data were collected from six separate studies where otherwise-identical pairs of mfPOP tests using either the original Continuous stimulus presentation method or the new CVs method were undertaken; 440 6-minute tests from 96 normal subjects of varying ages were included. Per-region SNRs were compared between the two methods., Results: Mean SNRs for the CVs mfPOP variants were between 35% and 57% larger than the original Continuous mfPOP variants (P < 0.001 in five of six studies). Similarly, the goodness-of-fit measure (r2) demonstrated large and significant fold increases of between 2.3× and 3.4× over the original method (all P < 0.001). Significant improvements in SNRs were present in all of the 88 test regions (44/eye), ranging between 8.4% and 93.7%; mean SNRs were significantly larger in 98% of test subjects., Conclusions: The CVs mfPOP stimulus presentation method produced substantial increases in signal quality over the original method. This is likely due to the stabilization of pupillary gain during stimulus presentation., Translational Relevance: These improvements increase diagnostic accuracy and have enabled shorter, 80-second mfPOP tests to be developed.

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.

Multifocal pupillographic objective perimetry (mfPOP) shows regions of slight hypersensitivity away from retinal regions damaged by diabetes or age-related macular degeneration (AMD). This study examines if such results also appear in multifocal visual evoked potentials (mfVEPs) recorded on the same day in the same patients. The pupil control system receives input from the extra-striate cortex, so we also examined evidence for such input. We recruited subjects with early type 2 diabetes (T2D) with no retinopathy, and patients with unilateral exudative AMD. Population average responses of the diabetes patients, and the normal fellow eyes of AMD patients, showed multiple regions of significant hypersensitivity (p < 0.05) on both mfPOP and mfVEPs. For mfVEPs the occipital electrodes showed fewer hypersensitive regions than the surrounding electrodes. More advanced AMD showed regions of suppression becoming centrally concentrated in the exudative AMD areas. Thus, mfVEP electrodes biased towards extra-striate cortical responses (surround electrodes) appeared to show similar hypersensitive visual field locations to mfPOP in early stage diabetic and AMD damage. Our findings suggest that hypersensitive regions may be a potential biomarker for future development of AMD or non-proliferative diabetic retinopathy, and may be more informative than visual acuity which remains largely undisturbed during early disease.

Purpose: This study investigated multifocal pupillographic objective perimetry (mfPOP) stimuli that target the intrinsic photosensitivity of melanopsin retinal ganglion cells. The diagnostic potential for glaucoma is compared between stimuli biased toward either cone input to these cells or their melanopsin response., Methods: Nineteen glaucoma patients and 24 normal subjects were tested using mfPOP stimulus protocols with either 33-ms yellow or 750-ms blue stimuli. Subjects' color discrimination was assessed using the Farnsworth 100-hue test. Pupillary responses were measured, and mixed-effects regression was used to quantify results. Diagnostic accuracy was assessed using receiver operating characteristic (ROC) analysis., Results: The mean reduction in moderate to severe glaucoma pupil responses using blue mfPOP stimuli was larger but more variable than that of the shorter yellow stimuli (blue: -1.32 dB [t(40) = -2.29; P = 0.027]; yellow: -0.93 dB [t(40) = -3.13; P = 0.003]). Color discrimination decreased significantly with age and glaucoma, with type III blue-yellow anomalies dominating. ROC analysis revealed similar diagnostic accuracies (AUC for eyes classified as moderate to severe; blue: 81.7%, yellow: 83.7). Slightly higher sensitivity and specificity were obtained using blue stimuli in mild disease (AUCs blue: 71.1, cf. yellow: 67.7), although this difference was not significant., Conclusions: In moderate to severe glaucoma, diagnostic accuracy of yellow and blue was similar, but blue stimuli showed limited ability to resolve scotomas. Blue mfPOP stimuli, however, may have advantages over yellow in detecting early glaucoma.

Purpose: Retinal light sensitivity loss has been shown to occur prior to other signs of retinopathy and may predict the sight-threatening sequelae. A rapid, objective perimetric test could augment diabetes care. We investigated the clinical use of multifocal pupillographic objective perimetry (mfPOP) to identify patients with and without diabetic retinopathy., Methods: Retinopathy severity was determined using the Early Treatment of Diabetic Retinopathy Study (ETDRS) standard for fundus photography. Pupillary responses were measured from both eyes of 25 adults with none to moderate diabetic retinopathy and 24 age-matched controls, using three mfPOP stimulus variants. Multifocal pupillographic objective perimetry stimulus variants tested 44 regions per eye arranged in a five-ring dartboard layout presented within either the central 30° or 60° of fixation. Receiver operator characteristic (ROC) curves were produced from contraction amplitudes and time to peak responses., Results: Regression analysis revealed that mean amplitude deviations were larger with severity of early retinopathy. On average, the longest delays were measured in patients with no retinopathy. The brightest wide-field stimuli produced the highest area under the ROC curve for differentiating eyes with no retinopathy from nonproliferative diabetic retinopathy (NPDR) and from healthy eyes (100 ± 0.0%, mean ± SE). The asymmetry in local delay deviations between eyes tended to produce higher sensitivity and specificity than amplitude deviations., Conclusions: Asymmetry in local response delays measured by mfPOP may provide useful information regarding the severity of diabetic retinopathy and may have clinical use as a rapid, noninvasive method for identifying functional loss even in the absence of NPDR.

Background: This study investigated the diagnostic utility for glaucoma of multifocal pupillographic objective perimetry stimuli targeting different components of the pupillary response: cortically derived colour responses and subcortical luminance responses., Design: Observational cross-sectional study undertaken at the Australian National University., Participants: Thirty-five eyes of 24 glaucoma subjects and 46 eyes of 23 normal subjects., Methods: Subjects were tested with three multifocal pupillographic objective perimetry stimulus variants. The luminance-only variant (YYbal) utilized yellow stimuli on a yellow background; mixed colour and luminance protocols utilized green stimuli on a red background (RGbal, RG). Stimuli of 33 ms duration were presented at mean intervals of 4 s/region., Main Outcome Measures: Pupil constriction amplitude and time to peak. Area under the receiver operating characteristic curve was the main measure of sensitivity and specificity for glaucoma., Results: Colour and luminance protocols were more accurate at differentiating glaucoma subjects from normal subjects than the luminance-only protocol, and produced the largest reductions in amplitudes. This type of protocol also produced the highest overall sensitivity and specificity for glaucoma (receiver operating characteristic % area under the curve: severe, 100%; moderate, 94.4%; mild, 71.0%). Pattern deviations tended to produce higher area under the receiver operating characteristic curves in eyes classified as mild. Significant differences in the means of the six worst amplitude deviations were observed between normal and severe glaucoma subjects only., Conclusions: Stimuli targeting both cortical pupillary colour response and subcortical pupillary luminance response components produced higher diagnostic accuracy than stimuli targeting subcortical pupillary luminance responses alone. Inclusion of constriction latencies further improved accuracy., (© 2014 Royal Australian and New Zealand College of Ophthalmologists.)

Background: Multifocal pupillographic objective perimetry was compared using 24 and 44 regions per visual field., Design: Experimental design in a university setting., Participants: Twenty-seven normal control and 36 age-matched glaucoma patients., Methods: The four test variants differed in the mean interval between stimuli: 4, 1 or 0.25 s; and the number of visual field regions tested within the central 60 degrees: 24 or 44. All subjects had their diagnostic status confirmed by optical coherence tomography, two forms of perimetry and slit-lamp biomicroscopy. Both eyes were measured concurrently in 2.73 ± 0.45 min/eye (mean ± standard deviation), and tests were repeated about 2 weeks apart., Main Outcome Measures: The main outcome measures were: (i) mean change in light sensitivity due glaucoma; and (ii) areas under Receiver Operator Characteristic plots for detecting glaucoma., Results: For all four variants, consensual responses, female gender and age produced small but significant sensitivity differences, and sensitivity declined with age by ≤-0.27 dB/decade (all P < 0.0003). The best diagnostic accuracy (area under curve 93.2 ± 3.89%) was produced by the one-presentation/s 44-region protocol. Across the four protocols, the effect of repeat testing was small (all methods ≤0.15 dB)., Conclusions: Presentation rate had little effect, but increasing the tested density from 24 to 44 regions/field improved diagnostic power. Given that multifocal pupillographic objective perimetry also provides information on response delay and afferent versus efferent defects at every visual field region, it may be a useful adjunct to perimetry., (© 2012 The Authors. Clinical and Experimental Ophthalmology © 2012 Royal Australian and New Zealand College of Ophthalmologists.)

Purpose: We are developing multifocal pupillographic objective perimetry (mfPOP) to assess localized changes in function within visual pathways. In this study, we investigate novel mfPOP stimuli designed to target neural components from either or both the sub-cortical pupillary luminance response and the cortically driven color response., Methods: Pupillary responses of 12 subjects were recorded to eight mfPOP stimulus variants (protocols). Forty-eight visual field test-regions (24/eye) were stimulated concurrently with uncorrelated sequences of either high or low luminance-contrast, luminance- plus color-contrast, or equiluminant color-exchange stimuli. Stimulus pulses were of 50 ms duration and were presented at mean intervals of 4 seconds/region. Test durations were 4 or 8 minutes; therefore, estimated responses were derived from 60 or 120 stimulus presentations to each test region., Results: Pupillary response amplitudes were more influenced by luminance-contrast than the color-contrast of stimuli; response delays, however, were more closely linked to the proportion of color- versus luminance-contrast in each protocol. Significant differences (P < 0.05) in amplitudes but not delays were present between all three high luminance-contrast protocols and a low luminance-contrast luminance protocol, regardless of color content. The reverse pattern was observed between the equiluminant color exchange protocol and this same low luminance-contrast luminance protocol. Only the low luminance-contrast plus color exchange protocol differed significantly from the low luminance-contrast luminance protocol in both measures., Conclusions: Two protocols, utilizing low and high luminance-contrast plus color exchange, were identified as likely to incorporate both cortical and subcortical response components, and were deemed potential candidates for further investigation in clinical studies.

Purpose: We compared the diagnostic power of 10 stimulus variants that assessed the visual fields of both eyes by recording pupillary responses to multifocal stimuli. The 10 variants comprised 6 initial tests, and 4 subsequent variants whose design was informed by the initial results., Methods: Two study groups containing 16 normal and 22 primary open angle glaucoma subjects, and 15 normal and 20 primary open angle glaucoma subjects had their diagnostic status verified by a slit-lamp investigation, applanation tonometry, 3 forms of perimetry, and Stratus OCT. Stereoscopically arranged displays presented multifocal stimulus arrays having 24 stimulus regions/eye within the central 60 degrees. Pupil responses were recorded by video cameras under infrared illumination. The 10 stimulus conditions varied in presentation rate, duration, stimulus luminance, and flicker rate. Stimuli were 4 minutes in duration, presented in 8 segments of 30 seconds. Up to 15% of the data of a segment could be lost owing to blinks and fixation losses without repeating the segment., Results: Each recording gave 96 direct and consensual responses/subject. The best performing stimulus method gave a sensitivity of 1.0 ± 0.0 (mean ± SE) for moderate and severe glaucomatous fields combined at a false positive rate of 0.05. Median signal to noise ratios for peak response amplitude expressed as t-statistics exceeded 4 for several variants., Conclusions: Stimulus delivery rates of about 1 presentation/region/s and test luminance around 150 cd/m performed best diagnostically. Unlike automated perimetry, the mfPOP method provides information on response delays and afferent and efferent defects at each region of the visual field.

Purpose: To investigate the efficacy of multifocal pupillographic objective perimetry (mfPOP) to quantify the effects of intravitreal ranibizumab injection for choroidal neovascularization (CNV) secondary to exudative age-related macular degeneration (AMD)., Methods: mfPOP visual fields from 20 patients with unilateral exudative AMD treated with intravitreal ranibizumab were measured before and after 3 months of treatment and were compared with that in 30 normal subjects. Two stimulus types consisting of ensembles of 24 or 44 independent stimuli per eye had a mean presentation interval at each region of 1 second. Pupil responses were recorded with video cameras under infrared illumination. Multiple linear models were fitted to contraction amplitudes and delay to peak responses, to determine the independent effects of exudative AMD before and after ranibizumab therapy., Results: After 3 months of treatment, mean additional response delays compared to normal subjects for the 24-region stimulus improved significantly (P < 5 × 10⁻⁹) from a mean of 18.82 ± 3.0 ms at baseline to 7.45 ± 3.15 ms. The mean effect of exudative AMD at baseline decreased constriction amplitude by -1.11 ± 0.24 dB (P < 0.00001) with little improvement after ranibizumab therapy. Small pretreatment elevations of extrafoveal sensitivity correlated with improvements in central retinal thickness (CRT) after treatment (P < 0.0005)., Conclusions: Improvements in mfPOP contraction amplitudes and time to peak responses were measured in eyes treated with intravitreal ranibizumab; however, response delays appeared to be the most indicative of functional improvement. Confirmation of hypersensitivity in the extrafoveal field in a larger group may support this finding as a prognostic marker for good treatment outcomes.

Purpose: We investigated issues that could impair the capacity of multifocal pupilliographic perimetry to detect visual field damage. Differential blue light absorbance causes between-subject variance so we compared stimuli with differing blue content. We also quantified declining response gain at higher stimulus intensities (saturation), which can reduce sensitivity to changes in the visual field., Methods: Independent stimuli were delivered to 44 regions of both eyes whereas pupil responses were recorded under infrared illumination. Luminance-response functions were measured at 88 locations for white, yellow, and red stimuli at luminances ranging from 36 to 288 cd/m2. Response saturation was quantified by fitting power functions: Response =α Luminance, z<1 indicating declining response gain. Experiments were conducted on 2 groups containing 16 and 18 different normal subjects. The second experiment was designed to confirm the results of the first and to include red stimuli., Results: Response saturation occurred in all visual field regions: the mean exponents ranged from 0.57 ± 0.01 to 0.74 ± 0.02 (mean ± SE), that is up to 30 SE away from an exponent of 1 (no saturation). The stimulus-response functions appeared to be determined by luminance rather than color. Signal to noise ratios and regional visual field sensitivities were similar for all stimulus colors., Conclusions: Response saturation was a feature of all visual field locations. Stimuli with reduced blue light content produced the same signal to noise ratios as white stimuli. Given that these stimuli would not be affected by variable lens brunescence, they might be preferable for perimetry.

Purpose: To investigate the neural basis of contraction anisocoria and any implications for assessments using pupillary responses, through analysis of topographic variation in amplitudes of direct and consensual pupil responses., Methods: Direct and consensual pupillary contraction amplitudes were analyzed from six studies in which 120 normal subjects were tested with 24 different stimulus variants. The dichoptically presented multifocal stimulus arrays subtended ± 30° of visual field but varied in color (achromatic or yellow), number of test regions (24 to 60/eye), mean regional presentation interval (0.25 to 16 s), and pulse time-course (33 to 150 ms, flickered or steady). The 290 cd/m(2) test-regions were displayed on a 10 cd/m(2) background. Ratios between mean direct and consensual responses were calculated for each region. Results were quantified using multivariate linear analysis., Results: Direct responses within the temporal hemifield were significantly larger than consensual for all stimulus protocols. Across the 24 protocols these differences ranged between 13.8% (t(1415)=3.06, P<0.01) and 27.0% (t(990)=5.72, P<0.0001). Differences in the nasal field were mostly non-significant. Contraction amplitudes varied systematically across the visual field. By contrast, direct/consensual ratios were markedly uniform within each hemifield., Conclusions: The distribution of signal from the pretectal olivary nuclei to each Edinger-Westphal nucleus differs depending on the hemifield being stimulated. A simple model incorporating segregation and summation of afferent signals, and differing saturation of midbrain pathways is proposed. This appears to explain inconsistent observations in the literature and predicates the need for separate assessment of direct and consensual responses at hemifield or better resolution., (Copyright 2011 The Association for Research in Vision and Ophthalmology, Inc.)

Purpose: The recent development of an objective and noninvasive perimetric technique using pupillary responses to sparse multifocal visual stimuli shows promise for the assessment of visual function in glaucoma. This study assesses the sensitivity and specificity of four variants of dichoptic multifocal pupillographic objective perimetry (mfPOP) with a high-resolution, 40-region/field stimulus., Methods: Nineteen normal subjects and 17 with open-angle glaucoma were tested with four 4-minute stimulus protocols, presented in eight segments of 30 seconds each. Achromatic multifocal stimuli comprised 40 test regions per eye arranged in a four-ring dartboard layout subtending 60° of visual field. Background luminance was 10 cd/m² with active stimulus regions displaying steady or flickered stimuli at 290 cd/m². Stimulus durations were between 33 and 150 ms, mean intervals between presentations to each test region ranged from 1 to 16 seconds. Fixation was monitored in real time., Results: Longer mean intervals and durations resulted in better diagnostic performance. Best results were obtained with 150-ms flickered stimuli and a discriminant function that incorporated both amplitude and width of responses: ROC area under the curve 0.86 ± 0.05 (mean ± SE) across all visual field severities, (n = 34) and 1.00 ± 0.00 for moderate and severe fields (n = 10)., Conclusions: mfPOP produces separate information on response delay and afferent and efferent defects at every point in the field. The diagnostic accuracy of the 40-region, 150-ms stimulus is comparable to that of commonly used subjective perimeters and encourages further investigation of this technique.

Multifocal pupillographic objective perimetry (mfPOP) has the advantage of being a non-invasive, objective method for measuring up to 88 visual field responses from both eyes concurrently within 5min. To date mfPOP has been used to assess the peripheral visual field. Here we examine the practicality of mfPOP for testing the macular region of the visual field. This study examines variations in temporal presentation rate, spatial stimulus layout and luminance intensity in a group of normal subjects to determine the optimal parameters for achieving high signal to noise ratios for a macular version of mfPOP. Responses to multifocal stimuli comprising 24 or 44 stimulus regions per eye were measured dichoptically achieving median signal to noise ratios of 2.47 z-score units. Long stimulus presentation intervals combined with 24 region non-overlapping layouts produced the largest contraction amplitudes and shortest response delays., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Purpose: Multifocal pupillographic perimetry was used to examine differences in the visual fields of 23 subjects with early type 2 diabetes (T2D) and 23 age- and sex-matched control subjects., Methods: Independent stimuli were delivered to 44 regions of each eye while pupil responses were recorded with infrared cameras. The stimuli were presented in 8 segments of 30 seconds, and both eyes of each subject were tested twice. The direct and consensual responses provided 88 responses per eye. The diagnostic power of the method was then examined by applying receiver operator analysis to the peak regional contraction amplitudes, time to peaks, and linear combinations of those., Results: Dichoptic multifocal pupillography provided response amplitudes with a median z-score of 2.63 +/- 0.26 (SE). The diagnostic performance (expressed as areas under ROC plots) of the eight subjects (32 fields) who had had T2D for at least 10 years was 0.87 +/- 0.06 (mean +/- SE) for response amplitude deviations from normative data, rising to 0.95 +/- 0.04 when between-eye symmetry was considered. Mean pupil size did not have diagnostic power. Comparison of direct and consensual response fields indicated that the observed localized field defects were afferent., Conclusions: Reasonable diagnostic power was obtained, especially for the 16 eyes that had had T2D for more than 10 years, inferring that even in the near absence of visible diabetic retinopathy, some retinal damage had been sustained. This result, if confirmed in a wider group, suggests the that the method may be clinically useful in screening for early damage to the retina in T2D diabetes.

Purpose: This preliminary study investigated a means of concurrently assessing the visual field defects of both eyes by recording pupillary responses to multifocal stimuli., Methods: Twenty normal subjects and 26 primary open angle glaucoma patients, age and sex matched, were examined by slit-lamp, Humphrey Field Analyser II achromatic 24-2 perimetry and fundus photography. The patients had moderate to severe fields in at least one eye. Two stereoscopically arranged displays presented an array of 24 stimulus regions per eye extending from fixation to 30 degrees eccentricity. Pupil responses were recorded by video cameras under infrared illumination. Four stimulus conditions were tested: each stimulus region containing either a single or a 2 x 2 array of patches, presented either steadily for 133 ms or flickered at 15 Hz for 266 ms. Mean presentation rate was 1/s/region. The 4-min duration stimuli were presented in 8 segments of 30 s. Segments did not need to be repeated unless more than 15% of a segment record was lost as a result of blinks or fixation losses., Results: The 48 stimuli produced 96 direct and consensual responses per subject. The single patch, non-flickered stimulus condition produced the best diagnostic performance, an area under the curve of 84%. The contraction amplitudes for that stimulus gave a median z-score of 3.2., Conclusions: The method produced diagnostic accuracy approaching that of automated perimetry, but unlike perimetry provides standard errors for every point in each field as well as information on response delay and efferent defects. Only one pupil needs to function to measure both visual fields.

Objective: To determine the sensitivity and specificity of blue-on-yellow multifocal visual evoked potentials (mfVEPs) in early glaucoma., Design: Cross-sectional study., Participants: Fifty patients with a confirmed diagnosis of early glaucoma and 60 normal participants., Methods: Black-and-white mfVEPs and blue-on-yellow mfVEPs were recorded using the Accumap version 2.0 (ObjectiVision Pty. Ltd., Sydney, Australia). All patients also underwent achromatic standard automated perimetry (SAP)., Main Outcome Measures: Multifocal VEP amplitude and latency values in glaucoma patients were analyzed and compared with those of the normal controls., Results: Based on the definition of visual field defect, in the group of glaucomatous eyes with SAP defects, amplitude of blue-on-yellow mfVEP was abnormal in all 64 cases (100% sensitivity), whereas black-and-white mfVEP missed 5 cases (92.2% sensitivity). Generally, larger scotomata were noted on blue-on-yellow mfVEP compared with black-and-white mfVEP for the same eyes. There was high topographic correspondence between SAP and amplitude of blue-on-yellow mfVEP and significant (P<0.0001) correlation between them (correlation coefficient, 0.73). Abnormal amplitude was detected in 3 of 60 eyes of control subjects (95% specificity). There was, however, no correlation between visual field defect and latency delay in glaucoma patients. Although there was a significant difference between averaged latency of control and glaucoma eyes, values considerably overlapped., Conclusions: The blue-on-yellow mfVEP is a sensitive and specific tool for detecting early glaucoma based on amplitude analysis.

In non-human primates at least three anatomically and functionally distinct channels convey signals from the retina to the primary visual cortex (V1). Two of these channels, the parvocellular and the koniocellular, are sensitive to chromatic contrasts and form the basis of color vision. In humans, common phylogenetic history with other primates and psychophysical experiments suggest identical retinocortical mechanisms but separate evaluation of the distinct anatomical channels has been difficult because signals are already combined in V1. We studied the spatial distribution of activation to chromatic stimuli along the two opponent chromatic axes in human V1 with multifocal functional magnetic resonance imaging. The signal strength was quantified from three experiments with stimuli up to 20 degrees eccentricity. The hypothesis was that, although the parvo- and koniocellular signals are mixed in V1, distinct distributions of signal strength would be evident. We found that whereas different conditions activated the same areas of cortex, indicating that they have identical magnification factors, the responses to red/green stimulation were stronger close to the fovea whereas the blue/yellow responses were much less diminished with increasing eccentricity. Both chromatic axes showed saturating contrast response functions. Our measure directly from human V1 is in line with earlier psychophysical studies suggesting relatively stronger parvocellular channel representation close to the fovea, and more uniform distribution of the koniocellular and achromatic channels. In addition, our study presents a way to rapidly quantify retinotopic signal transmission in distinct retinocortical pathways of individual subjects.

Visual evoked responses to dichoptically presented multifocal stimuli were recorded for 92 eyes. Two stimulus variants were explored: temporally sparse and rapidly contrast reversing. We used hierarchical decomposition (HD) to represent the multifocal responses in terms of a small number of potentially unique component waveforms that are interrelated in a multivariate linear autoregressive (MLAR) relationship. The HD method exploits temporal correlations over a range of delays in the responses to estimate parallel, feedforward and feedback relationships between the HD components. Three HD components having temporal interrelationships constrained (at P < 0.05) to a moving approximately 20 ms window could describe the multifocal responses well (median r2-values up to 90%). HD components were similar for both stimulus types and the component waveforms were temporally correlated, especially the first and third components. The data set was large enough to estimate separate HD components for each multifocal stimulus region. The component waveforms differed somewhat by region but the MLAR relationships were similar. At short delays parallel processing dominated. At longer delays the proportion of response drives that were attributed to feedback and feedforward relationships grew. Overall HD analysis seems to provide an informed summary of multifocal responses and insights into their sources.

Purpose: To define the pattern-pulse multifocal visual evoked potential (PPMVEP) and determine its characteristics in a sample of normal subjects in terms of amplitude of response attainable, the variation in waveform across visual field, and distribution of potential over the scalp and to compare pattern-pulse with contrast-reversal multifocal stimuli., Methods: VEPs were obtained by concurrently stimulating 60 regions of a cortically scaled dartboard with pulses of pattern contrast. Responses were recorded from normal subjects, by using a 32-channel electroencephalogram recording system, and elementary responses to each region were estimated by multiple regression of each of the response channel signals on stimulus signals. Left-eye, right-eye, and binocular viewing conditions were concurrently tested by dichoptic stimulation. A direct comparison was then made with contrast-reversal stimulation., Results: Response waveform sets for 12 subjects varied in maximum amplitude from 1.8 to 6.8 micro V. A stereotypical distribution of waveforms held in most subjects, depending primarily on the polar angle location of the stimulus within the visual field. In a direct comparison with a contrast-reversal multifocal analysis, the pattern-pulse responses had similar waveforms and scalp topography, but were 15 times larger in amplitude. Root mean square (RMS) signal-to-noise ratio (SNR) was 1.9 times higher with pattern-pulse stimulation, corresponding to a reduction of 73% in recording time to achieve the same SNR., Conclusions: The PPMVEP can simultaneously characterize 60 regions of the visual field for both eyes in less than 7 minutes. A general methodology is illustrated that allows multifocal analysis with flexible choice of stimulus conditions.

Purpose: A pattern electroretinogram (PERG) in which stimuli displaying the frequency-doubling (FD) illusion are presented simultaneously to multiple parts of the visual field was evaluated for its ability to diagnose glaucoma. This multiregion FD PERG is referred to in the current study as the MFP., Methods: The nine stimulus regions were temporally modulated at incommensurate frequencies typically producing an FD percept. Two other spatial scales of the stimuli were also investigated. The sensitivity and specificity of MFP were examined using linear and quadratic discriminant methods., Results: Even with the simpler linear discriminant classification, sensitivities and specificities of 100% were obtained in eyes with moderate to severe glaucoma. Of eyes with glaucoma strongly suspected, 67% were classified as being glaucomatous. Stimulus patterns having differing spatial scales produced different PERG visual field dependencies., Conclusions: The differing results for the 16-fold change in spatial scale may reflect the accessing of different mechanisms. The MFP method appears to have significant value for the diagnosis of glaucoma.

Purpose: A pattern electroretinogram (PERG) simultaneously displaying the frequency-doubling (FD) illusion in nine parts of the visual field was compared with two other methods for ability to detect glaucoma. This multiregion FD PERG (MFP) was compared with results from achromatic automated perimetry and psychophysical tests using FD stimuli., Methods: MFP data were compared with that from the Humphrey Field Analyser (HFA; Humphrey, San Leandro, CA) 24-2 program. Contrast thresholds were also determined in different visual field locations for FD stimuli. Thin-plate spline methods were used to derive comparisons from the tests, each of which sampled the visual field differently., Results: Significant correlation with HFA could be obtained, providing seven to nine (of nine) MFP amplitudes were themselves significant. Evidence showed that both the psychophysical tests using FD stimuli and the MFP detect glaucomatous damage not detected by the HFA., Conclusions: The comparisons between HFA perimetry, the MFP, and FD thresholds indicate that both FD-based tests quantify a form of diffuse loss in early glaucoma as well as the scotomas of later glaucoma.

In 13 wallabies (Macropus eugenii, the tammar), microelectrode recordings of the activity of units in the superficial layers of the superior colliculus in response to a flashing light spot were used to make a map of the spatial location of their receptive fields. This article describes the projection of a normal eye to the contralateral colliculus. Ten of the 13 animals had one rotated eye and these projections are analysed in the accompanying paper (James et al., this issue). Units responded briskly to the stimulus at light on and off and had receptive fields about 5 degrees across. The centres of receptive fields from a regular array of recording points on the colliculus were plotted with a perimeter and fitted to a flattened representation of the colliculus according to a spline technique. The visual field of each colliculus extends from 25 degrees ipsilateral to the vertical meridian to 120 degrees temporal contralaterally. The lines of isoazimuth are regularly spaced and parallel and run mediolaterally on the colliculus. The horizon is represented by a line running rostrocaudally and the parallels are more widely spaced near the horizon and become compressed in the superior and inferior fields. The variation of areal magnification factor fits the distribution of density of retinal ganglion cells very well. Anisotropy of the projection means that the increased ganglion cell density of the retinal visual streak is entirely accommodated by magnification in the vertical direction, while the magnification of the azimuthal projection is equal over the whole field. No responses were recorded from the ipsilateral eye even though anatomically there is a direct retinal ipsilateral projection.

At about the time of eye opening, one eye of seven tammar wallaby pouch young was surgically rotated about the optic axis by approximately 90 degrees. In adulthood the projection of the visual field through the rotated eye onto the contralateral superior colliculus was mapped electrophysiologically. Although apparently distorted, the projection could be coherently re-rotated mathematically to a reasonable copy of the normal projection from the opposite eye of the same animal, including details such as regional variations of the magnification factor. The same was true of three adult animals in which the eye rotation was done after anaesthesia immediately before the electrophysiological mapping. In animals in which the visual field seen through one eye, the other being normal, was rotated for the entire period of visual experience, there was no sign of compensation or rearrangement of the topographic map. Retinocollicular synaptic connections appear unmoved by such discordant visual experience.