Effect of shorter dark adaptation on ISCEV standard DA 0.01 and DA 3 skin ERGs in healthy adults

A New Approach to Staging Diabetic Eye Disease: Staging of Diabetic Retinal Neurodegeneration and Diabetic Macular Edema

Topic

The goal of this review was to summarize the current level of evidence on biomarkers to quantify diabetic retinal neurodegeneration (DRN) and diabetic macular edema (DME).

Clinical relevance

With advances in retinal diagnostics, we have more data on patients with diabetes than ever before. However, the staging system for diabetic retinal disease is still based only on color fundus photographs and we do not have clear guidelines on how to incorporate data from the relatively newer modalities into clinical practice.

Methods

In this review, we use a Delphi process with experts to identify the most promising modalities to identify DRN and DME. These included microperimetry, full-field flash electroretinogram, spectral-domain OCT, adaptive optics, and OCT angiography. We then used a previously published method of determining the evidence level to complete detailed evidence grids for each modality.

Results

Our results showed that among the modalities evaluated, the level of evidence to quantify DRN and DME was highest for OCT (level 1) and lowest for adaptive optics (level 4).

Conclusion

For most of the modalities evaluated, prospective studies are needed to elucidate their role in the management and outcomes of diabetic retinal diseases.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Enhancing Electroretinogram Classification with Multi-Wavelet Analysis and Visual Transformer

The electroretinogram (ERG) is a clinical test that records the retina's electrical response to light. Analysis of the ERG signal offers a promising way to study different retinal diseases and disorders. Machine learning-based methods are expected to play a pivotal role in achieving the goals of retinal diagnostics and treatment control. This study aims to improve the classification accuracy of the previous work using the combination of three optimal mother wavelet functions. We apply Continuous Wavelet Transform (CWT) on a dataset of mixed pediatric and adult ERG signals and show the possibility of simultaneous analysis of the signals. The modern Visual Transformer-based architectures are tested on a time-frequency representation of the signals. The method provides 88% classification accuracy for Maximum 2.0 ERG, 85% for Scotopic 2.0, and 91% for Photopic 2.0 protocols, which on average improves the result by 7.6% compared to previous work.

Human retinal dark adaptation tracked in vivo with the electroretinogram: insights into processes underlying recovery of cone- and rod-mediated vision

The substantial time taken for regaining visual sensitivity (dark adaptation) following bleaching exposures has been investigated for over a century. Psychophysical studies yielded the classic biphasic curve representing recovery of cone-driven and rod-driven vision. The electroretinogram (ERG) permits direct assessment of recovery at the level of the retina (photoreceptors, bipolar cells), with the first report over 70 years ago. Over the last two decades, ERG studies of dark adaptation have generated insights into underlying physiological processes. After large bleaches, rod photoreceptor circulating current, estimated from the rod-isolated bright-flash ERG a-wave, takes 30 min to recover, indicating that products of bleaching, thought to be free opsin (unbound to 11-cis-retinal), continue to activate phototransduction, shutting off rod circulating current. In contrast, cone current, assessed with cone-driven bright-flash ERG a-waves, recovers within 100 ms following similar exposures, suggesting that free opsin is less able to shut off cone current. The cone-driven dim-flash a-wave can be used to track recovery of cone photopigment, showing regeneration is 'rate-limited' rather than first order. Recoveries of the dim-flash ERG b-wave are consistent also with rate-limited rod photopigment regeneration (where free opsin, desensitising the visual system as an 'equivalent background', is removed by rate-limited delivery of 11-cis-retinal). These findings agree with psychophysical and retinal densitometry studies, although there are unexplained points of divergence. Post-bleach ERG recovery has been explored in age-related macular degeneration and in trials of visual cycle inhibitors for retinal diseases. ERG tracking of dark adaptation may prove useful in future clinical contexts.

An alternative electroretinography protocol for children: a study of diagnostic agreement and accuracy relative to ISCEV standard electroretinograms

PURPOSE

To assess the diagnostic accuracy and agreement between a paediatric electroretinography protocol used at Great Ormond Street Hospital (GOSH-ERG) and the 'gold standard' international protocol (ISCEV-ERG) in health and disease.

METHODS

Patient databases between 2010 and 2020 were screened to identify children with an ISCEV-ERG recorded within four years of a GOSH-ERG. Electroretinogram (ERG) component peak times and amplitudes were re-measured, and data were analysed in terms of absolute abnormality and proportional deviation from respective reference ranges. Abnormality was defined by the retinal system affected and by individual ERG a- and b-wave component analysis.

RESULTS

A total of 59 patients were included: 38 patients had retinal disease defined by an abnormal ISCEV-ERG and 21 had normal ISCEV-ERGs. When absolute abnormality was defined by combined retinal systems, the GOSH-ERG showed an excellent overall sensitivity of 95% (accuracy 86%). Individual retinal systems showed good-excellent sensitivity (67%-100%) and specificity (68%-97%). Electroretinogram (ERG) component sensitivities ranged between 60% and 97% and specificities between 79% and 97% dependent upon the protocol step. The proportional relationship appeared mostly linear between protocols. Electroretinogram (ERG) morphology was comparable for both protocols in a range of retinal diseases including those with pathognomonic ERGs.

CONCLUSION

We demonstrate the high diagnostic accuracy of a paediatric ERG protocol (GOSH-ERG) relative to ISCEV standard ERGs. The close proportional deviation and similar waveform morphology indicate ERGs from each protocol are similarly affected in disease. This encourages the use of the GOSH-ERG protocol in the screening, diagnosis and monitoring of retinal disease in children who are unable to comply with the rigorous ISCEV-ERG protocol.

In vivo evaluation of outer retinal function and structure after retrobulbar optic nerve crush by lateral orbitotomy in goats

Large animal model of optic nerve crush (ONC) plays an important role in translating novel therapeutic strategies developed in rodent model to clinical application. Due to the poor accessibility of the optic nerve (ON) in humans and large animals, lateral orbitotomy is needed to expose the retrobulbar ON. This study was to explore the effects of ONC and ON exposure with lateral orbitotomy (sham surgery) on the outer retinal function and structure in goats by using standard flash electroretinogram (FERG) and spectral-domain optical coherence tomography (SD-OCT). We found that ONC led to a transient reduction in FERG amplitudes at 1 week post injury (wpi), which recovered gradually over 2 months afterwards. Sham surgery alone also caused a similar pattern of amplitude reduction in FERG, although not as significantly as ONC did. Transient outer retinal thickening following ONC occurred at 4 wpi (when progressive thinning of the ganglion cell complex began), peaked at 8 wpi, then recovered gradually at 12 wpi. In contrast, outer retinal thickness remained unchanged statistically 3 months after sham surgery. Fundus fluorescein angiography showed that neither ONC nor ON exposure with lateral orbitotomy significantly caused any significant delay or absence of central retinal vascular filling. In summary, ONC with lateral orbitotomy affects outer retinal function and structure transiently.

Evolution of the retinal function by flash-ERG in one child suffering from neuronal ceroid lipofuscinosis CLN2 treated with cerliponase alpha: case report

INTRODUCTION

Neuronal ceroid lipofuscinoses (CLN) are neurodegenerative disorders among the most frequent, inherited as an autosomal recessive trait. Affected patients can present with progressive decline in cognitive and motor functions, seizures, a shortened life span and visual deficiency. CLN2 is one of the rare CLN that benefits from treatment by cerliponase alpha an enzyme replacement therapy. Preliminary results on treated animal models have shown delayed neurological signs and prolonged life span. However, cerliponase alpha did not prevent vision loss or retinal degeneration in those animal models. Cerliponase alpha has currently been delivered to a few CLN2-affected patients. We report the case of one patient suffering from CLN2 treated with intracerebroventricular infusions of cerliponase alpha 300 mg every two weeks. Evolution of his retinal function was assessed by three successive flash-ERG and flash-VEP recordings throughout his treatment over a 4-year period.

RESULTS

Before treatment at the age of 4 years 5 months, patient's retinas were normal (normal fundi and normal flash-ERG). After 29 infusions at the age of 6 years 10 months, a-wave combined response was absent, while cone and flicker responses were normal. After 80 infusions at the age of 8 years 9 months, a-wave cone response was absent with b-wave peak time increased, and no combined response.

COMMENTS

Despite treatment, our patient's retinas showed a progressive abnormal and inhomogeneous function. Rods function was altered first, then the scotopic system and afterward, the cones. This result differs from those recorded in animal models. The relative preservation of cone functioning for a while could not be unequivocally attributed to enzyme replacement therapy as we lack comparison with the evolution of flash-ERGs recorded in untreated subjects.

ERG shrinks by 10% when reducing dark adaptation time to 10 min, but only for weak flashes

PURPOSE

To compare dark-adapted (DA) ERG between 10, 15 and 20 min of dark adaptation (DA).

METHODS

In a counterbalanced random block design, 40 healthy adult subjects were dark-adapted for 10, 15 or 20 min before we recorded ERGs to nine flash strengths from 0.001 to 10.0 cd s/m2 (dilated pupils) with a DTL-like electrode. Before and between sessions, the room was lit. Apart from choosing a wider range of stimulus strengths, and adding shorter DA times, the recordings fully complied with the ISCEV ERG Standard, namely using corneal electrodes, mydriasis and a standard DA sequence.

RESULTS

The a-wave amplitude was not affected by any adaptation condition. For the b-wave amplitude, effects of reduced DA time are stronger for weaker flashes: Reducing DA from 20 to 10 min had no measurable effect on the DA 3 ERG, but reduced the DA 0.01 b-wave significantly (p < 0.0001) to 87 ± 2% (mean ± SEM). The DA 0.001 b-wave (not part of the ISCEV ERG Standard) was more affected (down to 72 ± 4%). There was a small, but significant, increase, only for weak flashes, in a- and b-wave peak times for 20 compared to 10-min dark adaptation time.

CONCLUSION

Reducing dark adaptation time from 20 to 10 min in normal participants has no effect on the ISCEV DA 3 and DA 10 ERG. The reduction in DA 0.01 ERGs to 87 ± 2% agrees with Hamilton and Graham (Doc Ophthalmol 133:11-19, 2016. https://doi.org/10.1007/s10633-016-9554-x ) who found 90 ± 2% and with Asakawa et al. (Doc Ophthalmol 139:33-44, 2019. https://doi.org/10.1007/s10633-019-09693-8 ) who found 83%. Pending verification in pathophysiological states, the current results suggest that one might be able to correct for the 10% amplitude loss when gaining 10 min through shortened DA.

People with current major depression resemble healthy controls on flash Electroretinogram indices associated with impairment in people with stabilized schizophrenia

Flash electroretinography (fERG) has been used to identify anomalies in retinal functioning in several psychiatric disorders. In schizophrenia (SCZ), fERG abnormalities are reliably observed, but findings from studies of major depressive disorder (MDD) have been less consistent. In this study, fERG data were recorded from MDD patients in a current major depressive episode (n = 25), and compared to data from SCZ patients (n = 25) and healthy controls (HC; n = 25), to determine the degree to which fERG anomalies in acute MDD overlap or contrast with those observed in stabilized (though not symptom free) SCZ. The primary variables of interest were a-wave (photoreceptor activity), b-wave (bipolar-Müller cell activity), and photopic negative response (PhNR; ganglion cell activity) amplitudes and implicit times. Across most conditions, there were no significant differences between the MDD and HC groups in a- or b-wave response, but the SCZ group consistently demonstrated reduced amplitudes. Interestingly, MDD patients demonstrated an increase in photopic a-wave implicit time relative to SCZ patients, and a decrease in PhNR implicit time relative to controls. Correlations between BDI-II scores and fERG metrics were not significant for either patient group. Overall, these data indicate that, using an fERG protocol that distinguishes SCZ patients from controls, MDD patients experiencing a current depressive episode closely resemble healthy controls in their fERG responses. Therefore, MDD-related fERG changes may be more subtle than those observed in SCZ and detectable only with larger sample sizes than we employed and/or using a different set of fERG test parameters.

Adaptation time, electroretinography, and pupillography in healthy subjects

PURPOSE

To investigate the relationship between adaptation time and the parameters of electroretinography (ERG) and pupillography in healthy subjects.

METHODS

Forty-six eyes of 23 healthy women (mean age 21.7 years) were enrolled. ERG and pupillography were tested in each of the right and left 23 eyes, respectively. ERG with a skin electrode was used to determine amplitude and implicit time by the records of rod-, flash-, cone-, and flicker-responses with white light (0.01-30 cd s/m²). Infrared pupillography was used to record the pupillary light reflex to 1-s stimulation of red light (100 cd/m²). Cone- and flicker- (rod-, flash- and pupil) responses were recorded after light (dark) adaptation at 1, 5, 10, 15, and 20 min.

RESULTS

Amplitude (µV) was significantly different between 1 min and ≥ 5 or ≥ 10 min after adaptation in b-wave of cone- or rod-response, respectively. Implicit time (ms) differed significantly between 1 min and ≥ 5 min after adaptation with b-wave of cone- and rod-response. There were significant differences between 1 min and ≥ 10 or ≥ 5 min after dark adaptation in parameter of minimum pupil diameter (mm) or constriction rate (%), respectively.

CONCLUSIONS

Cone-driven ERG can be recorded, even in 5 min of light adaptation time without any special light condition, whereas rod-driven ERG and pupillary response results can be obtained in 10 min or longer of dark adaptation time in complete darkness.

Dark-adapted red flash ERGs in healthy adults

Purpose

The x-wave of the dark-adapted (DA) ERG to a red flash reflects DA cone function. This exploratory study of healthy adults aimed to investigate changes in the DA red ERG with flash strength and during dark adaptation to optimise visualisation and therefore quantification of the x-wave.

Methods

The effect of altering red flash strength was investigated in four subjects by recording ERGs after 20 min dark adaptation to red flashes (0.2–2.0 cd s m⁻²) using skin electrodes and natural pupils. The effect of dark adaptation duration was investigated in 16 subjects during 20 min in the dark, by recording DA 1.5 red ERGs at 1, 2, 3, 4, 5, 10, 15 and 20 min.

Results

For a dark adaption period of 20 min, the x-wave was more clearly visualised to weaker (< 0.6 cd s m⁻²) red flash strengths: to stronger flashes it became obscured by the b-wave. For red flashes of 1.5 cd s m⁻², the x-wave was most prominent in ERGs recorded after 1–5 min of dark adaptation: with longer dark adaptation, it was subsumed into the b-wave’s rising edge.

Conclusions

This small study suggests that x-wave visibility in healthy subjects after 20 min dark adaptation is improved by using flashes weaker than around 0.6 cd s m⁻²; for flash strengths of 1.5 cd s m⁻², x-wave visibility is enhanced by recording after only around 5 min of dark adaptation. No evidence was found that interim red flash ERGs affect the dark-adapted state of the normal retina.

The diagnostic usefulness of the negative electroretinogram

The definition of the negative response of the full field electroretinogram is the presence of a b-wave with less amplitude than the a-wave (b/a ratio<1) in the combined response of cones and rods. The presence of this pattern reflects an alteration in the bipolar cells, the Müller cells, or in the transmission of the stimulus from the photoreceptors to the bipolar cells, with preserved photoreceptor function. This finding can be seen bilaterally and symmetrically in different hereditary conditions, such as congenital stationary night blindness, juvenile X-linked retinoschisis, and Duchenne and Becker muscular dystrophies. On the other hand, it can also be found unilaterally (or asymmetrically) in acquired pathologies, such as some types of immuno-mediated retinitis (Birdshot retinochoroiditis), autoimmune retinopathies, cancer/melanoma associated retinopathy, or retinal toxicity. The objective of this review is to summarise the characteristics of the pathologies in which this finding can be observed, in order to highlight its usefulness in the differential diagnosis of retinal conditions.