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Frontiers in Molecular Neuroscience 2023Vertebrate rods and cones operate over a wide range of ambient illumination, which is provided by light adaptation mechanisms regulating the sensitivity and speed of the...
Vertebrate rods and cones operate over a wide range of ambient illumination, which is provided by light adaptation mechanisms regulating the sensitivity and speed of the phototransduction cascade. Three calcium-sensitive feedback loops are well established in both rods and cones: acceleration of the quenching of a light-activated visual pigment and cGMP synthesis by guanylate cyclase, and increased affinity of ion channels for cGMP. Accumulating evidence suggests that the molecular mechanisms of light adaptation are more complex. While investigating these putative mechanisms, we discovered a novel phenomenon, observing that the recovery of light sensitivity in rods after turning off non-saturating adaptive light can take tens of seconds. Moreover, after a formal return of the membrane current to the dark level, cell sensitivity to the stimuli remains decreased for a further 1-2 min. We termed this phenomenon of prolonged photoreceptor desensitization 'adaptation memory' (of previous illumination) and the current study is focused on its detailed investigation in rods and an attempt to find the same phenomenon in cones. In rods, we have explored the dependencies of this phenomenon on adapting conditions, specifically, the intensity and duration of adapting illumination. Additionally, we report that fish and frog red-sensitive cones possess similar features of adaptation memory, such as a drop in sensitivity just after the steps of bright light and slow sensitivity recovery. However, we have found that the rate of this process and its nature are not the same as in rods. Our results indicate that the nature of the temporary drop in the sensitivity in rods and cones after adapting steps of light is different. In the rods, adaptation memory could be attributed to the existence of long-lasting modifications of the components of the phototransduction cascade after adapting illumination. In cones, the observed form of the adaptation memory seems to be due to the sensitivity drop caused by a decrease in the availability of the visual pigment, that is, by bleaching.
PubMed: 37168678
DOI: 10.3389/fnmol.2023.1135088 -
Ophthalmology and Therapy Mar 2021Dark adaptation (DA) has been proposed as a possible functional biomarker for age-related macular degeneration (AMD). In this systematic review we aim to evaluate... (Review)
Review
INTRODUCTION
Dark adaptation (DA) has been proposed as a possible functional biomarker for age-related macular degeneration (AMD). In this systematic review we aim to evaluate current methodology used to assess DA in people with AMD, the evidence of precision in detecting the onset and progression of AMD, and the relationship between DA and other functional and structural measures.
METHODS
MEDLINE, EMBASE, CINAHL, AMED, PsycINFO, PsycARTICLES were searched for studies published between January 2006 and January 2020 that assessed DA in people with AMD. Details of eligible studies including study design, characteristics of study population and outcomes were recorded. All included studies underwent quality appraisal using approved critical appraisal tools. This systematic review follows PRISMA guidelines (PROSPERO registration number: CRD42019129486).
RESULTS
Forty-eight studies were eligible for inclusion, reporting a variety of instruments and protocols to assess different DA parameters. Twenty of these studies used the AdaptDx (MacuLogix, Hummelstown, PA, USA) instrument and assessed rod-intercept time (RIT). Most of these reported that RIT was delayed in people with AMD and this delay worsened with AMD severity. Four studies, involving 533 participants, reported estimates of diagnostic performance of AdaptDx to separate people with AMD from visually healthy controls. DA has been compared to other measures of visual function, patient-reported outcome measures (PROMs) and structural measures. Ten studies specifically considered evidence that the presence of certain structural abnormalities was associated with impaired DA in AMD.
CONCLUSIONS
This systematic review indicates overwhelming evidence of reasonable quality for an association between impaired DA and AMD. Data on the repeatability and reproducibility of DA measurement are sparse. There is evidence that structural abnormalities such as reticular drusen are associated with prolongation of DA time. Fewer studies have explored an association between DA and other measures of visual function or PROMs. We found no studies that had compared DA with performance-based measures.
PubMed: 33565038
DOI: 10.1007/s40123-020-00323-0 -
Translational Vision Science &... Jul 2023The purpose of this study was to assess test-retest variability and discriminatory power of measures from macular integrity assessment (S-MAIA) and AdaptDx.
Test-Retest Variability and Discriminatory Power of Measurements From Microperimetry and Dark Adaptation Assessment in People With Intermediate Age-Related Macular Degeneration - A MACUSTAR Study Report.
PURPOSE
The purpose of this study was to assess test-retest variability and discriminatory power of measures from macular integrity assessment (S-MAIA) and AdaptDx.
METHODS
This is a cross-sectional study of 167 people with intermediate age-related macular degeneration (iAMD), no AMD (controls; n = 54), early AMD (n = 28), and late AMD (n = 41), recruited across 18 European ophthalmology centers. Repeat measures of mesopic and scotopic S-MAIA average (mean) threshold (MMAT decibels [dB] and SMAT [dB]) and rod intercept time (RIT [mins]) at 2 visits 14 (±7) days apart were recorded. Repeat measures were assessed by Bland-Altman analysis, intra-class correlation coefficients (ICCs) and variability ratios. Secondary analysis assessed the area under the receiver operating characteristic curves (AUC) to determine the ability to distinguish people as having no AMD, early AMD, or iAMD.
RESULTS
Data were available for 128, 131, and 103 iAMD participants for the mesopic and scotopic S-MAIA and AdaptDx, respectively. MMAT and SMAT demonstrate similar test-retest variability in iAMD (95% confidence interval [CI] ICC of 0.79-0.89 and 0.78-0.89, respectively). ICCs were worse in RIT (95% CI ICC = 0.55-0.77). All tests had equivalent AUCs (approximately 70%) distinguishing between subjects with iAMD and controls, whereas early AMD was indistinguishable from iAMD on all measures (AUC = <55%). A learning effect was not seen in these assessments under the operating procedures used.
CONCLUSIONS
MMAT, SMAT, and RIT have adequate test-retest variability and are all moderately good at separating people with iAMD from controls.
TRANSLATIONAL RELEVANCE
Expected levels of test-retest variability and discriminatory power of the AdaptDx and MAIA devices in a clinical study setting must be considered when designing future trials for people with AMD.
Topics: Humans; Dark Adaptation; Visual Field Tests; Cross-Sectional Studies; Macular Degeneration
PubMed: 37477933
DOI: 10.1167/tvst.12.7.19 -
The Journal of Physiology Nov 2022The substantial time taken for regaining visual sensitivity (dark adaptation) following bleaching exposures has been investigated for over a century. Psychophysical... (Review)
Review
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.
Topics: Humans; Dark Adaptation; Retinaldehyde; Retinal Rod Photoreceptor Cells; Photic Stimulation; Electroretinography; Retinal Cone Photoreceptor Cells; Retina; Opsins
PubMed: 35612091
DOI: 10.1113/JP283105 -
Documenta Ophthalmologica. Advances in... Aug 2018The 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...
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) 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) red flash strengths: to stronger flashes it became obscured by the b-wave. For red flashes of 1.5 cd s m, 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; for flash strengths of 1.5 cd s m, 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.
Topics: Adult; Dark Adaptation; Electroretinography; Female; Healthy Volunteers; Humans; Male; Middle Aged; Photic Stimulation; Retinal Cone Photoreceptor Cells; Young Adult
PubMed: 29858967
DOI: 10.1007/s10633-018-9642-1 -
Translational Vision Science &... Jun 2020Functional studies of rods in age-related macular degeneration using the Medmont Dark-Adapted Chromatic Perimeter (DACP) have demonstrated impairments in scotopic...
PURPOSE
Functional studies of rods in age-related macular degeneration using the Medmont Dark-Adapted Chromatic Perimeter (DACP) have demonstrated impairments in scotopic sensitivities and dark adaptation (DA). We investigated the intersession repeatability of scotopic sensitivity and DA parameters including the rod intercept time recorded from the Medmont DACP.
METHODS
Scotopic thresholds (14 test points) and DA using a 30% photobleach (eight test points) were measured on two separate days from participants 50 years of age or older with a range of age-related macular degeneration severity at loci superior and inferior to the fovea. Repeatability coefficients were calculated for prebleach scotopic sensitivity, and for DA parameters including rod intercept time.
RESULTS
Twelve participants (mean age, 79.7 ± 8.1 years) repeated Medmont DACP testing within 50 days. Repeatability coefficients for prebleach scotopic sensitivity to long wavelength (red, 625 nm) and short wavelength (cyan, 505 nm) were 5.9 dB and 7.2 dB, respectively. The DA curve-derived repeatability coefficients for cone threshold was 3.9 dB, final threshold 5.3 dB, with an R value of 0.075 decades/min, rod intercept time 7.6 minutes, and RITslope 0.54 min/degree.
CONCLUSIONS
This study establishes repeatability coefficients for scotopic thresholds and multiple DA parameters obtained with the Medmont DACP in patients with age-related macular degeneration. These repeatability coefficients will serve as the basis for determining clinically meaningful change in rod function in future clinical trials.
TRANSLATIONAL RELEVANCE
Measures of repeatability parameters of scotopic thresholds and DA are essential to the accurate interpretation of results in future studies and trials using these measures.
Topics: Aged; Aged, 80 and over; Dark Adaptation; Fovea Centralis; Humans; Macular Degeneration; Retinal Cone Photoreceptor Cells
PubMed: 32832236
DOI: 10.1167/tvst.9.7.31 -
Journal of Behavioral Addictions Sep 2019Slot machines are a very popular form of gambling. In this study, we look at two different routes to enjoying slots play. One route involves the degree to which players...
BACKGROUND AND AIMS
Slot machines are a very popular form of gambling. In this study, we look at two different routes to enjoying slots play. One route involves the degree to which players react to rewards. The other route involves what we call dark flow - a pleasurable, but maladaptive state where players become completely engrossed in slots play, providing an escape from the depressing thoughts that characterize their everyday lives.
METHODS
One hundred and twenty-nine high-frequency slots players were tested on slot-machine simulators set up in the lobby of a casino. We measured reward reactivity using post-reinforcement pauses (PRPs) and the force with which players pressed the spin button following different slot-machine outcomes. For each player, we calculated the slopes of PRPs and force as a function of credit gains. We also assessed players' slots game enjoyment and their experience of dark flow, depression, and problem gambling.
RESULTS
Both the PRP and the force measures of reward reactivity were significantly correlated with players' enjoyment of the slots session, but neither measure was correlated with either problem gambling or depression. Ratings of dark flow were strongly correlated with slots enjoyment (which accounted for far more positive affect variance than the reward reactivity measures) and were correlated with both problem gambling scores and depression.
DISCUSSION AND CONCLUSIONS
Our results suggest that of these two routes to enjoying slot-machine play, the dark flow route is especially problematic. We contend that the dark flow state may be enjoyable because it provides escape from the negative thoughts linked to depression.
Topics: Adaptation, Psychological; Adult; Aged; Aged, 80 and over; Anxiety; Depression; Female; Gambling; Humans; Male; Middle Aged; Pleasure; Reinforcement, Psychology; Reward; Stress, Psychological; Time Factors; Young Adult
PubMed: 31460768
DOI: 10.1556/2006.8.2019.38 -
Current Developments in Nutrition Oct 2020The DRI values for vitamin A were last reviewed and defined in 2001. At the time, there was very sparse data that could be used to set the DRI values for pregnancy,... (Review)
Review
The DRI values for vitamin A were last reviewed and defined in 2001. At the time, there was very sparse data that could be used to set the DRI values for pregnancy, lactation, and infancy. In the subsequent 20 y since the last formal review, a number of findings relevant to the adequacy indicator of visual dark adaptation in pregnancy, the usual vitamin A content of breast milk across lactation stages, and vitamin A metabolism in women and children have been published. Furthermore, identification of genetic variables affecting the bioconversion of provitamin A carotenoids to vitamin A have provided an improved explanation for interindividual variability in responses to provitamin A carotenoids. The purpose of this collection of articles, introduced herein, is to review and apply recent findings about vitamin A status, address current gaps in knowledge, and suggest avenues for future research needed to refine the DRI values for pregnancy, lactation, and early life.
PubMed: 32999953
DOI: 10.1093/cdn/nzaa096 -
Journal of Vision Mar 2019The cellular origins of slow ERG changes during light adaptation following a dark-adapted state are still unclear. To study light adaptation, six healthy, normal...
The cellular origins of slow ERG changes during light adaptation following a dark-adapted state are still unclear. To study light adaptation, six healthy, normal trichromats were dark-adapted for 30 min prior to full-field ERG recordings to sinusoidal stimuli that isolate responses of the L- or M-cones or that stimulate luminance and chromatic mechanisms at 12 or 36 Hz. Recordings were performed for 16 min with 2-min intervals after onset of a constant background. Generally, the responses were sine-wave-like, and the first harmonic (fundamental) component dominated the Fourier spectrum except for the 12-Hz luminance stimulus in which two components, a sine-wave-like component and a transient component, determined the response profiles, leading to large second harmonic components. The amplitude of the first harmonic component (F) increased as a function of the light-adaptation time except for the 12-Hz luminance stimulus at which the F component decreased as a function of the light-adaptation period. The phase of the first harmonic component changed only slightly (less than 30°) during the light-adaptation period for all stimuli conditions. The L/M ratio in luminance reflecting ERGs decreased with increasing adaptation time. Our present data suggest that the light-adaptation process mainly reflects changes in the luminance pathway. The responses to 12-Hz luminance stimuli are determined by two different luminance driven pathways with different adaptation characteristics.
Topics: Adaptation, Ocular; Adult; Color; Dark Adaptation; Electroretinography; Female; Healthy Volunteers; Humans; Luminescence; Male; Photic Stimulation; Retinal Cone Photoreceptor Cells
PubMed: 30916727
DOI: 10.1167/19.3.12 -
American Journal of Ophthalmology Case... Jun 2021To evaluate the effect of central serous chorioretinopathy (CSCR) on retinal function using dark adaptation in a human subject, and to follow it through resolution of...
PURPOSE
To evaluate the effect of central serous chorioretinopathy (CSCR) on retinal function using dark adaptation in a human subject, and to follow it through resolution of the disease.
PATIENTS
Single patient, 50 years old male patient, with acute CSCR in one eye and resolved old CSCR in the other eye.
OBSERVATIONS
Observational study in patient with CSCR followed through resolution of the subretinal fluid (52 days). Dark adaptation was assessed using the AdaptDx® (Maculogix Inc.) measured by Rod Intercept time (RIT) in minutes. A normal retinal locus of the same eye on the opposite side of the fovea was used as control. Retinal separation (microns) was measured using Spectralis Optical Coherence Tomography (Spectralis®, HRA + OCT, Heidelberg engineering). Change in time to dark adapt, were correlated with retinal separation measured in microns, during the course of CSCR.The Rod Intercept time was delayed in the area of detached retina compared to the normal region (control) on presentation with retinal separation (RS) of 104 μm. The Rod Intercept time returned to normal as the retinal separation from retinal pigment epithelium decreased and eventually resolved.
CONCLUSIONS
This case shows that delay in dark adaptation is proportional to the amount of separation of neurosensory retina from retinal pigment epithelium in CSCR, this may offer a potential of using DA to characterize visual function in CSCR. The association of dark adaptation response with the state of retinal pigment epithelial function and its ability to predict the recurrence of CSCR needs further evaluation.
PubMed: 33997469
DOI: 10.1016/j.ajoc.2021.101098