Luminance and colour variant pupil perimetry in glaucoma

The structure-function relationship between multifocal pupil perimetry and retinal nerve fibre layer in glaucoma

BACKGROUND

Multifocal pupillographic objective perimetry (mfPOP) is a novel method for assessing functional change in diseases like glaucoma. Previous research has suggested that, in contrast to the pretectally-mediated melanopsin response of intrinsically photosensitive retinal ganglion cells, mfPOP responses to transient onset stimuli involve the extrastriate cortex, and thus the main visual pathway. We therefore investigate the correlation between peripapillary retinal nerve fibre layer (pRNFL) thickness and glaucomatous visual field changes detected using mfPOP. Parallel analyses are undertaken using white on white standard automated perimetry (SAP) for comparison.

METHODS

Twenty-five glaucoma patients and 24 normal subjects were tested using SAP, 3 mfPOP variants, and optical coherence tomography (OCT). Arcuate clusters of the SAP and mfPOP deviations were weighted according to their contribution to published arcuate divisions of the retinal nerve fibre layer. Structure-function correlation coefficients (r) were computed between pRNFL clock-hour sector thickness measurements, and the local visual field sensitivities from both SAP and mfPOP.

RESULTS

The strongest correlation was observed in the superior-superotemporal disc sector in patients with worst eye SAP MD < -12 dB: r = 0.93 for the mfPOP LumBal test (p < 0.001). Correlations across all disc-sectors were strongest in these same patients in both SAP and mfPOP: SAP r = 0.54, mfPOP LumBal r = 0.55 (p < 0.001). In patients with SAP MD ≥ -6 dB in both eyes, SAP correlations across all sectors were higher than mfPOP; mfPOP correlations however, were higher than SAP in more advanced disease, and in normal subjects.

CONCLUSIONS

For both methods the largest correlations with pRNFL thickness corresponded to the inferior nasal field of more severely damaged eyes. Head-to-head comparison of mfPOP and SAP showed similar structure-function relationships. This agrees with our recent reports that mfPOP primarily stimulates the cortical drive to the pupils.

Discriminating early-stage diabetic retinopathy with subjective and objective perimetry

Introduction

To prevent progression of early-stage diabetic retinopathy, we need functional tests that can distinguish multiple levels of neural damage before classical vasculopathy. To that end, we compared multifocal pupillographic objective perimetry (mfPOP), and two types of subjective automated perimetry (SAP), in persons with type 2 diabetes (PwT2D) with either no retinopathy (noDR) or mild to-moderate non-proliferative retinopathy (mmDR).

Methods

Both eyes were assessed by two mfPOP test methods that present stimuli within either the central ±15° (OFA15) or ±30° (OFA30), each producing per-region sensitivities and response delays. The SAP tests were 24-2 Short Wavelength Automated Perimetry and 24-2 Matrix perimetry.

Results

Five of eight mfPOP global indices were significantly different between noDR and mmDR eyes, but none of the equivalent measures differed for SAP. Per-region mfPOP identified significant hypersensitivity and longer delays in the peripheral visual field, verifying earlier findings. Diagnostic power for discrimination of noDR vs. mmDR, and normal controls vs. PwT2D, was much higher for mfPOP than SAP. The mfPOP per-region delays provided the best discrimination. The presence of localized rather than global changes in delay ruled out iris neuropathy as a major factor.

Discussion

mfPOP response delays may provide new surrogate endpoints for studies of interventions for early-stage diabetic eye damage.

Early diabetic eye damage: Comparing detection methods using diagnostic power

It is now clear that retinal neuropathy precedes classical microvascular retinopathy in diabetes. Therefore, tests that underpin useful new endpoints must provide high diagnostic power well before the onset of moderate diabetic retinopathy. Hence, we compare detection methods of early diabetic eye damage. We reviewed data from a range of functional and structural studies of early diabetic eye disease and computed standardized effect size as a measure of diagnostic power, allowing the studies to be compared quantitatively. We then derived minimum performance criteria for tests to provide useful clinical endpoints. This included the criteria that tests should be rapid and easy so that children with type 1 diabetes can be followed into adulthood with the same tests. We also defined attributes that lend test data to further improve performance using Machine/Deep Learning. Data from a new form of objective perimetry suggested that the criteria are achievable.

Effects of Stimulus Luminance, Stimulus Color and Intra-Stimulus Color Contrast on Visual Field Mapping in Neurologically Impaired Adults Using Flicker Pupil Perimetry

Purpose

We improve pupillary responses and diagnostic performance of flicker pupil perimetry through alterations in global and local color contrast and luminance contrast in adult patients suffering from visual field defects due to cerebral visual impairment (CVI).

Methods

Two experiments were conducted on patients with CVI (Experiment 1: 19 subjects, age M and SD 57.9 ± 14.0; Experiment 2: 16 subjects, age M and SD 57.3 ± 14.7) suffering from absolute homonymous visual field (VF) defects. We altered global color contrast (stimuli consisted of white, yellow, cyan and yellow-equiluminant-to-cyan colored wedges) in Experiment 1, and we manipulated luminance and local color contrast with bright and dark yellow and multicolor wedges in a 2-by-2 design in Experiment 2. Stimuli consecutively flickered across 44 stimulus locations within the inner 60 degrees of the VF and were offset to a contrasting (opponency colored) dark background. Pupil perimetry results were compared to standard automated perimetry (SAP) to assess diagnostic accuracy.

Results

A bright stimulus with global color contrast using yellow (p= 0.009) or white (p= 0.006) evoked strongest pupillary responses as opposed to stimuli containing local color contrast and lower brightness. Diagnostic accuracy, however, was similar across global color contrast conditions in Experiment 1 (p= 0.27) and decreased when local color contrast and less luminance contrast was introduced in Experiment 2 (p= 0.02). The bright yellow condition resulted in highest performance (AUC M = 0.85 ± 0.10, Mdn = 0.85).

Conclusion

Pupillary responses and pupil perimetry's diagnostic accuracy both benefit from high luminance contrast and global but not local color contrast.

Rapid, non-contact multifocal visual assessment in multiple sclerosis

OBJECTIVE

Previous work on temporally sparse multifocal methods suggests that the results are correlated with disability and progression in people with multiple sclerosis (PwMS). Here, we assess the diagnostic power of three cortically mediated sparse multifocal pupillographic objective perimetry (mfPOP) methods that quantified response-delay and light-sensitivity at up to 44 regions of both visual fields concurrently.

METHODS

One high-spatial-resolution mfPOP method, P129, and two rapid medium-resolution methods, W12 and W20, were tested on 44 PwMS and controls. W12 and W20 took 82 s to test both visual fields concurrently, providing response delay and sensitivity at each field location, while P129 took 7 min. Diagnostic power was assessed using areas under the receiver operating characteristic (AUROC) curves and effect-size (Hedges' g). Linear models examined significance. Concurrent testing of both eyes permitted assessment of between-eye asymmetries.

RESULTS

Per-region response delays and asymmetries achieved AUROCs of 86.6% ± 4.72% (mean ± SE) in relapsing-remitting MS, and 96.5% ± 2.30% in progressive MS. Performance increased with increasing disability scores, with even moderate EDSS 2 to 4.5 PwMS producing AUROCs of 82.1 to 89.8%, Hedge's g values up to 2.06, and p = 4.0e - 13. All tests performed well regardless of any history of optic neuritis. W12 and W20 performed as well or better than P129.

CONCLUSION

Overall, the 82-s tests (W12 and W20) performed better than P129. The results suggest that mfPOP assesses a correlate of disease severity rather than a history of inflammation, and that it may be useful in the clinical management of PwMS.

Objective perimetry and progression of multiple sclerosis

Introduction

We re-examined the per-region response amplitudes and delays obtained from multifocal pupillographic objective perimetry (mfPOP) after 10 years in 44 persons living with multiple sclerosis (PwMS), both to examine which parts of the visual field had progressed in terms of response properties and to examine if the baseline data could predict the overall progression of disease.

Methods

Expanded Disability Status Scale (EDSS) scores were assessed in 2009 and 2019. Both eyes of each participant were concurrently tested at 44 locations/eye on both occasions. Several measures of clinical progression were examined, using logistic regression to determine the odds of progression.

Results

At the second examination the 44 PwMS (31 females) were aged 61.0 ± 12.2 y. Mean EDSS had not changed significantly (3.69 ± 1.23 in 2009, 3.81 ± 2.00 in 2019). mfPOP delay increased progressively from inferior to superior regions of the visual fields while amplitudes demonstrated a temporal to nasal gradient. The mean of the 3 most delayed visual field regions was correlated with progression of MS by 2019 (p = 0.023). Logistic regression indicated a significant association between delay and odds of progression (p = 0.045): an individual with 3 regions at least 1 SD (40 ms) slower than the mean in 2009 had 2.05× (±SE: 1.43× to 2.95×) the odds of progression by 2019. A 1 SD shorter delay was associated with 2.05× lower odds of progression. Amplitude changes were not predictive of progression.

Significance

mfPOP may provide a rapid, convenient method of monitoring and predicting MS progression.

Multifocal pupillographic objective perimetry for assessment of early diabetic retinopathy and generalised diabetes-related tissue injury in persons with type 1 diabetes

Background

To examine the potential utility of five multifocal pupillographic objective perimetry (mfPOP) protocols, in the assessment of early diabetic retinopathy (DR) and generalised diabetes-related tissue injury in subjects with type 1 diabetes (T1D).

Methods

Twenty-five T1D subjects (age 41.8 ± 12.1 (SD) years, 13 male) with either no DR (n = 13) or non-proliferative DR (n = 12), and 23 age and gender-matched control subjects (age 39.7 ± 12.9 years, 9 male) were examined by mfPOP using five different stimulus methods differing in visual field eccentricity (central 30° and 60°), and colour (blue, yellow or green test-stimuli presented on, respectively, a blue, yellow or red background), each assessing 44 test-locations per eye. In the T1D subjects, we assessed 16 metabolic status and diabetes complications variables. These were summarised as three principal component analysis (PCA) factors. DR severity was assessed using Early Treatment of Diabetic Retinopathy Study (ETDRS) scores. Area under the curve (AUC) from receiver operator characteristic analyses quantified the diagnostic power of mfPOP response sensitivity and delay deviations for differentiating: (i) T1D subjects from control subjects, (ii) T1D subjects according to three levels of the identified PCA-factors from control subjects, and (iii) TID subjects with from those without non-proliferative DR.

Results

The two largest PCA-factors describing the T1D subjects were associated with metabolic variables (e.g. body mass index, HbA1c), and tissue-injury variables (e.g. serum creatinine, vibration perception). Linear models showed that mfPOP per-region response delays were more strongly associated than sensitivities with the metabolic PCA-factor and ETDRS scores. Combined mfPOP amplitude and delay measures produced AUCs of 90.4 ± 8.9% (mean ± SE) for discriminating T1D subjects with DR from control subjects, and T1D subjects with DR from those without of 85.9 ± 8.8%. The yellow and green stimuli performed better than blue on most measures.

Conclusions/interpretation

In T1D subjects, mfPOP testing was able to identify localised visual field functional abnormalities (retinal/neural reflex) in the absence or presence of mild DR. mfPOP responses were also associated with T1D metabolic status, but less so with early stages of non-ophthalmic diabetes complications.

Handheld chromatic pupillometry can accurately and rapidly reveal functional loss in glaucoma

BACKGROUND/AIMS

Early detection and treatment of glaucoma can delay vision loss. In this study, we evaluate the performance of handheld chromatic pupillometry (HCP) for the objective and rapid detection of functional loss in glaucoma.

METHODS

In this clinic-based, prospective study, we enrolled 149 patients (median (IQR) years: 68.5 (13.6) years) with confirmed glaucoma and 173 healthy controls (55.2 (26.7) years). Changes in pupil size in response to 9 s of exponentially increasing blue (469 nm) and red (640 nm) light-stimuli were assessed monocularly using a custom-built handheld pupillometer. Pupillometric features were extracted from individual traces and compared between groups. Features with the highest classification potential, selected using a gradient boosting machine technique, were incorporated into a generalised linear model for glaucoma classification. Receiver operating characteristic curve analyses (ROC) were used to compare the performance of HCP, optical coherence tomography (OCT) and Humphrey Visual Field (HVF).

RESULTS

Pupillary light responses were altered in glaucoma compared with controls. For glaucoma classification, HCP yielded an area under the ROC curve (AUC) of 0.94 (95% CI 0.91 to 0.96), a sensitivity of 87.9% and specificity of 88.4%. The classification performance of HCP in early-moderate glaucoma (visual field mean deviation (VFMD) > -12 dB; AUC=0.91 (95% CI 0.87 to 0.95)) was similar to HVF (AUC=0.91) and reduced compared with OCT (AUC=0.97; p=0.01). For severe glaucoma (VFMD ≤ -12 dB), HCP had an excellent classification performance (AUC=0.98, 95% CI 0.97 to 1) that was similar to HVF and OCT.

CONCLUSION

HCP allows for an accurate, objective and rapid detection of functional loss in glaucomatous eyes of different severities.

Comparing Objective Perimetry, Matrix Perimetry, and Regional Retinal Thickness in Mild Diabetic Macular Edema

Purpose

To compare per-region macular sensitivity and delay from objective perimetry with Matrix perimetry and retinal thickness in mild diabetic macular edema (DMO).

Methods

Thirty-three patients with type 2 diabetes (T2D) aged 59.2 ± 10.5 years participated in a longitudinal study. Macular thickness, sensitivities and delays from the objectiveFIELD Analyzer (OFA), and Matrix perimeter sensitivities were mapped onto a common spatial layout to compute per-region correlations between structure/function measures. A generalized linear mixed-effects logistic regression model determined which variables contributed to clinical diagnosis of DMO.

Results

For OFA, the mean sensitivity differences compared with normal in patients with T2D were negative and the mean delay differences positive, indicating lowered sensitivities and prolonged delays, both increasing with diabetes duration. Shorter diabetes duration could produce either localized peripheral hypersensitivities or shorter delays. Functional change could occur when retinal thickness was stable. Peripheral macular thickness correlated with central and peripheral OFA sensitivity and delay, all P < 0.0012 in DMO and a median of P = 0.001 without DMO; this was not true for Matrix sensitivities. The logistic model determined that peripheral thickness, OFA sensitivity (P = 0.043), and time in the study (P = 0.001) contribute independently to the odds of DMO versus no DMO.

Conclusions

Mean sensitivities decreased and mean delays increased with duration of diabetes. Peripheral macular thickness correlated significantly with central and peripheral macular OFA sensitivity and delay. Peripheral macular thickness and functional measures may provide sensitive prognostic data.

Translational Relevance

Functional loss can precede structural change in DMO, so including such functional assessment for deciding on treatment may be beneficial.

The Relationship between Pupillometric Values and Visual Evoked Potential Test Results in Patients with Early Glaucoma

SIGNIFICANCE

Measuring pupil diameter may provide an additional objective method to detect and monitor glaucoma.

PURPOSE

The purposes of this study were to evaluate whether pupillometry can be used in the assessment of glaucomatous damage and to determine whether pupillometer can be used in glaucoma screening.

METHODS

In this retrospective study, patients with early stages of glaucomatous optic neuropathy were tested using visual evoked potential (VEP), standard automated perimetry, and pupillometer. The VEP record was made using two consecutive check sizes (1° and 15') at 1-Hz frequency. Patients with a mean deviation of <-2 and >-6 dB were included in the study. Pupil size measurements were performed under photopic conditions at 60-, 100-, and 130-cd/m luminance levels with the OPD Scan (Nidek, Gamagori, Japan) device.

RESULTS

In all, 24 eyes of 24 patients (14 women and 10 men) with newly diagnosed open-angle glaucoma were included, and 30 eyes of 30 healthy subjects (15 women, 15 men) were used as controls. There was no significant difference between sexes in photopic pupil diameters in either group. Comparing the pupil diameters in different luminance levels, the diameters were significantly larger in the patient group. When age-corrected values in the glaucoma group were compared with an age-matched control group, the differences in P100 latency and amplitudes were statistically significant. There were significant correlations between photopic pupil diameters and timing of VEP waveforms.

CONCLUSIONS

There is a relationship between pupil diameters and VEP results in eyes with early glaucoma.

Recovery dynamics of multifocal pupillographic objective perimetry from tropicamide dilation

PURPOSE

To study the pupillary system by combining mydriasis and multifocal pupillographic objective perimetry (mfPOP). In particular, we explored how the dynamics of recovery differ for concurrently measured direct and consensual sensitivity, response delay, and signal-to-noise ratios (SNRs) for binocular mydriasis.

METHODS

We recruited 26 normal participants, all with brown irides. The dichoptic mfPOP stimuli concurrently assessed 44-region/eye and both pupils. Two pre-dilation tests were followed by pairs of repeated tests at 1, 2, 4, 6, 8, 12, 24, and 48 h following dilation of both pupils with 1% tropicamide. Three subjects were retested with only the right pupil dilated. Linear models determined the independent effects of mydriasis upon the per-region and pupil measures over time.

RESULTS

Post-dilation, the per-region delays initially decreased by 16.3 ± 6.02 ms (mean ± SE) (p < 0.0001, cf. baseline of 471.1 ± 4.36 ms), then increased to slower than baseline by 17.42 ± 5.57 ms after 4 h (p < 0.002), recovering to baseline at 8 h. By comparison, per-region sensitivities (constriction amplitudes) were still reduced by - 6.20 ± 0.70 μm at 8 h (p < 0.0001, cf. baseline of 21.1 ± 0.55 μm), recovered at 24 h, but rebounded at 48 h (p = 0.005). The SNRs for sensitivities and delays both recovered by 8-12 h. Across all the data, sensitivities reduced by 2.67 ± 0.25 μm/decade of age, and delay increased by 15.4 ± 1.98 ms/decade (both p < 0.00001). Data from 3 of the 26 subjects who repeated the testing for monocular dilation found that consensual response sensitivities were larger than direct for 8 h (p < 0.018).

CONCLUSIONS

The per-region sensitivities were affected for longer than SNRs or delays. Strong early SNRs indicated proportionately lower pupil noise for larger pupil diameters. Following mydriasis with tropicamide 1%, the constriction amplitude measurements with mfPOP should be considered only after 48 h, but time-to-peak can be measured after 8-12 h.

Localization of Neuronal Gain Control in the Pupillary Response

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.

Gaze-Contingent Flicker Pupil Perimetry Detects Scotomas in Patients With Cerebral Visual Impairments or Glaucoma

Background: The pupillary light reflex is weaker for stimuli presented inside as compared to outside absolute scotomas. Pupillograph perimetry could thus be an objective measure of impaired visual processing. However, the diagnostic accuracy in detecting scotomas has remained unclear. We quantitatively investigated the accuracy of a novel form of pupil perimetry.

Methods: The new perimetry method, termed gaze-contingent flicker pupil perimetry, consists of the repetitive on, and off flickering of a bright disk (2 hz; 320 cd/m²; 4° diameter) on a gray background (160 cd/m²) for 4 seconds per stimulus location. The disk evokes continuous pupil oscillations at the same rate as its flicker frequency, and the oscillatory power of the pupil reflects visual sensitivity. We monocularly presented the disk at a total of 80 locations in the central visual field (max. 15°). The location of the flickering disk moved along with gaze to reduce confounds of eye movements (gaze-contingent paradigm). The test lasted ~5 min per eye and was performed on 7 patients with cerebral visual impairment (CVI), 8 patients with primary open angle glaucoma (age >45), and 14 healthy, age/gender-matched controls.

Results: For all patients, pupil oscillation power (FFT based response amplitude to flicker) was significantly weaker when the flickering disk was presented in the impaired as compared to the intact visual field (CVI: 12%, AUC = 0.73; glaucoma: 9%, AUC = 0.63). Differences in power values between impaired and intact visual fields of patients were larger than differences in power values at corresponding locations in the visual fields of the healthy control group (CVI: AUC = 0.95; glaucoma: AUC = 0.87). Pupil sensitivity maps highlighted large field scotomas and indicated the type of visual field defect (VFD) as initially diagnosed with standard automated perimetry (SAP) fairly accurately in CVI patients but less accurately in glaucoma patients.

Conclusions: We provide the first quantitative and objective evidence of flicker pupil perimetry's potential in detecting CVI-and glaucoma-induced VFDs. Gaze-contingent flicker pupil perimetry is a useful form of objective perimetry and results suggest it can be used to assess large VFDs with young CVI patients whom are unable to perform SAP.

Retinotopic effects of visual attention revealed by dichoptic multifocal pupillography

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.

Pupillometric evaluation of the melanopsin containing retinal ganglion cells in mitochondrial and non-mitochondrial optic neuropathies

In recent years, chromatic pupillometry is used in humans to evaluate the activity of melanopsin expressing intrinsic photosensitive retinal ganglion cells (ipRGCs). Blue light is used to stimulate the ipRGCs and red light activates the rod/cone photoreceptors. The late re-dilation phase of pupillary light reflex is primarily driven by the ipRGCs. Optic neuropathies i.e. Leber hereditary optic neuropathy (LHON), autosomal dominant optic atrophy (ADOA), nonarteritic anterior ischemic optic neuropathy (NAION), glaucoma, optic neuritis and idiopathic intracranial hypertension (IIH) are among the diseases, which have been subject to pupillometric studies. The ipRGCs are differentially affected in these various optic neuropathies. In mitochondrial optic neuropathies, the ipRGCs are protected against degeneration, whereas in glaucoma, NAION, optic neuritis and IIH the ipRGCs are damaged. Here, we will review the results of pupillometric, histopathological and animal studies evaluating the ipRGCs in mitochondrial and non-mitochondrial optic neuropathies.

Comparing multifocal pupillographic objective perimetry (mfPOP) and multifocal visual evoked potentials (mfVEP) in retinal diseases

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.