Red Flashes Research Articles

Brain mechanism of acupuncture for children with anisometropic amblyopia: a resting functional magnetic resonance imaging study based on voxel-mirrored homotopic connectivity.

To explore the brain mechanism of acupuncture for children with anisometropic amblyopia using the voxel-mirror homotopic connectivity (VMHC) analysis method of resting functional magnetic resonance imaging (rs-fMRI) technology based on clinical effectiveness. Eighty children with anisometropic monocular amblyopia were randomly divided into two groups: control (40 cases, 1 case of shedding) and acupuncture (40 cases, 1 case of shedding) groups. The control group was treated with glasses, red flash, grating, and visual stimulations, with each procedure conducted for 5min per time. Based on routine treatment, the acupuncture group underwent acupuncture of "regulating qi and unblocking meridians to bright eyes", Jingming (BL1), Cuanzhu (BL2), Guangming (GB37), Fengchi (GB20) acupoints were taken on both sides, with the needle kept for 30min each time. Both groups were treated once every other day, three times per week, for a total of 4wk. After the treatment, the overall curative effect of the two groups and the latency and amplitude changes of P100 wave of pattern visual-evoked potential were counted. At the same time, nine children with left eye amblyopia were randomly selected from the two groups and were scanned with rs-fMRI before and after treatment. The differences in the brain regions between the two groups were compared and analyzed with VMHC. Chi-square test showed a notable difference in the total efficiency rate between the acupuncture (94.87%) and control groups (79.49%). Regarding the P100 wave latency and amplitude, the acupuncture group had significantly shorter latency and higher amplitude of P100 wave than the control group. Moreover, the VMHC values of the bilateral temporal lobe, superior temporal gyrus, and middle temporal gyrus were notably increased in the acupuncture group after treatment. Acupuncture combined with conventional treatment can significantly improve the corrected visual acuity and optic nerve conduction in children with anisometropic amblyopia. Compared with the conventional treatment, the regulation of acupuncture on the functional activities of the relevant brain areas in the anterior cerebellum may be an effective acupuncture mechanism for anisometropic amblyopia.

Update on the range of visual electrophysiology tests and heir application with clinical examples

The International Society for clinical electrophysiology of vision (ISCEV) publishes open‐access standards and guidelines for routine electrophysiological tests of the visual system in order to optimize diagnostic value, to promote consistency and to allow meaningful inter‐laboratory comparisons. The ISCEV also publishes extended protocols with the aim of promoting convergence of methods that are not yet standardized, for tests that are widely used but often performed as an addition to the minimum ISCEV standard procedures (see www.ISCEV.org for all publications).This talk will outline the main ISCEV standard methods including the full‐field electroretinogram (ERG), pattern ERG (PERG) and multifocal ERG (mfERG). Several extended full‐field ERG protocols will also be highlighted, including the dark‐adapted (DA) red flash ERG, photopic On–Off ERG and S‐cone ERG. The use of these methods in the clinic will be illustrated in cases of inherited and acquired retinal disorders, to show how the extended protocols complement standard techniques, to aid diagnosis and patient management and to probe and detail retinal function phenotypes.The Standard full‐field ERG is recorded under dark‐adapted (DA) and light‐adapted (LA) conditions and provides a measure of generalized rod and cone system function at the level of the outer and inner retina, with minimal contribution from the macula. The mfERG assesses cone system function across the posterior pole and the PERG assesses macular and macular retinal ganglion cell function.The DA red flash ERG is an extended protocol that provides a measure of generalized dark‐adapted retinal function, with the advantage of having both a cone system x‐wave and a rod system b‐wave within the same waveform. This enables the relative involvement of rod and cone systems to be assessed simultaneously and can help determine the origins of severely attenuated standard DA strong flash ERGs. The DA red flash ERG is also useful for assessing cone system function in photophobic patients, and in patients with variable ability to comply with longer ERG protocols. The photopic On–Off ERG is a response to an extended light stimulus (duration 150 or 200 ms) and is used to assess generalized cone system function of both the On and Off retinal pathways, useful when there is a locus of dysfunction that is post‐phototransduction or post‐receptoral, when On and Off retinal systems may be similarly, selectively or specifically affected e.g., in different forms of congenital stationary night blindness (CSNB) or in forms of toxic retinopathy. The S‐cone ERG (short‐wavelength or “blue” flash ERG) is used to probe the function of the S‐cone retinal pathway, and can aid diagnosis and characterization in a variety of retinal dystrophies and disorders e.g., distinguishing between achromatopsia and S‐cone monochromacy.

The diagnostic accuracy of photopic negative responses evoked by broadband and chromatic stimuli in a clinically heterogeneous population

PurposeTo compare the diagnostic accuracy of the photopic negative response (PhNR) elicited by red-blue (RB) and white-white (WW) stimuli, for detection of retinal ganglion cell (RGC) dysfunction in a heterogeneous clinical cohort.MethodsAdults referred for electrophysiological investigations were recruited consecutively for this single-centre, prospective, paired diagnostic accuracy study. PhNRs were recorded to red flashes (1.5 cd·s·m−2) on a blue background (10 cd·m−2) and to white flashes on a white background (the latter being the ISCEV standard LA 3 stimulus). PhNR results were compared with a reference test battery assessing RGC/optic nerve structure and function including optical coherence tomography (OCT) retinal nerve fibre layer thickness and mean RGC volume measurements, fundus photography, pattern electroretinography and visual evoked potentials. Primary outcome measures were differences in sensitivity and specificity of the two PhNR methods.ResultsTwo hundred and forty-three participants were initially enrolled, with 200 (median age 54; range 18–95; female 65%) meeting inclusion criteria. Sensitivity was 53% (95% confidence intervals [CI] 39% to 68%) and 62% (95% CI 48% to 76%), for WW and RB PhNRs, respectively. Specificity was 80% (95% CI 74% to 86%) and 78% (95% CI 72% to 85%), respectively. There was a statistically significant difference between sensitivities (p = 0.046) but not specificities (p = 0.08) of the two methods. Receiver operator characteristic (ROC) area under the curve (AUC) values were 0.73 for WW and 0.74 for RB PhNRs.ConclusionPhNRs to red flashes on a blue background may be more sensitive than white-on-white stimuli, but there is no significant difference between specificities. This study highlights the value and potential convenience of using white-on-white stimuli, already used widely for routine ERG assessment.

Utility of Light-Adapted Full-Field Electroretinogram ON and OFF Responses for Detecting Glaucomatous Functional Damage.

To compare parameters of electroretinogram (ERG) responses for their ability to detect functional loss in early stages of nonhuman primate (NHP) experimental glaucoma (EG), including photopic negative responses (PhNR) to a standard brief red flash on a blue background (R/B) and 200-ms-long R/B and white-on-white (W/W) flashes, to W/W flicker stimuli (5-50Hz), and to a dark-adapted intensity series. Light-adapted ERGs were recorded in 12 anesthetized monkeys with unilateral EG. Amplitudes and implicit times of the a-wave, b-wave, and d-wave were measured, as well as amplitudes of PhNRs and oscillatory potentials for flash onset and offset. Flicker ERGs were measured using peak-trough and fundamental frequency analyses. Dark-adapted ERG parameters were modeled by Naka-Rushton relationships. Only PhNR amplitudes were significantly reduced in EG eyes compared to fellow control (FC) eyes. The d-wave implicit time was delayed in EG versus FC eyes only for the W/W long flash, but in all eyes it was 10 to 20 ms slower for R/B versus the W/W condition. Flicker ERGs were <0.5 ms delayed in EG versus FC overall, but amplitudes were affected only at 5Hz. The brief R/B PhNR amplitude had the highest sensitivity to detect EG and strongest correlation to parameters of structural damage. The PhNR to the standard brief R/B stimulus was best for detecting and following early-stage functional loss in NHP EG. These results suggest that there would be no benefit in using longer duration flashes to separate onset and offset responses for clinical management of glaucoma.

Full-field electroretinogram recorded with skin electrodes in 6- to 12-year-old children

PurposeTo determine the full-field electroretinogram (ffERG) parameters, including the light-adapted (LA) 3 ERG and the photopic negative response (PhNR), in 6- to 12-year-old children.MethodsffERG data were obtained from 214 eyes of 214 healthy subjects. The amplitudes and peak time of the ffERG responses were obtained from children divided into 6- to 8-year-old and 9- to 12-year-old groups. Using a skin electrode, electrical signals were measured in response to white stimulating light and white background light (LA 3 ERG). A blue background light and red flashes were then used to elicit the PhNR.ResultsThe a-wave amplitude ranged from 0.40 to 9.20 μV, the b-wave ranged from 4.70 to 30.80 μV, and the PhNR ranged from 1.30 to 39.90 μV. The b-wave peak time (33.20 ms) of 6- to 8-year-old groups was slightly shorter than that of the 9- to 12-year-old groups (33.60 ms, P = 0.01), but no differences in amplitudes or in peak time of other components. There were significant correlations between the amplitudes (a-wave and b-wave: r = 0.43, p < 0.001; a-wave and PhNR: r = 0.25, p < 0.001; b-wave and PhNR: r = 0.45, p < 0.001). There was a moderate correlation between the a-wave and b-wave peak time (r = 0.31, P < 0.001).ConclusionsWe determined the largest dataset of the LA 3 ERG and PhNR parameters in a population of healthy children, aged 6–12 years, which may provide a useful reference value when evaluating children with potential retinal defects.

Long-term blue light rearing does not affect in vivo retinal function in young rhesus monkeys.

Exposure to blue light is thought to be harmful to the retina. The purpose of this study was to determine the effects of long-term exposure to narrowband blue light on retinal function in rhesus monkeys. Young rhesus monkeys were reared under short-wavelength "blue" light (n = 7; 465nm, 183 ± 28lx) on a 12-h light/dark cycle starting at 26 ± 2days of age. Age-matched control monkeys were reared under broadband "white" light (n = 8; 504 ± 168lx). Light- and dark-adapted full-field flash electroretinograms (ERGs) were recorded at 330 ± 9days of age. Photopic stimuli were brief red flashes (0.044-5.68cd.s/m2) on a rod-saturating blue background and the International Society for Clinical Electrophysiology of Vision (ISCEV) standard 3.0 white flash on a 30cd/m2 white background. Monkeys were dark adapted for 20min and scotopic stimuli were ISCEV standard white flashes of 0.01, 3.0, and 10cd.s/m2. A-wave, b-wave, and photopic negative response (PhNR) amplitudes were measured. Light-adapted ERGs in young monkeys were compared to ERGs in adult monkeys reared in white light (n = 10; 4.91 ± 0.88years of age). For red flashes on a blue background, there were no significant differences in a-wave (P = 0.46), b-wave (P = 0.75), and PhNR amplitudes (P = 0.94) between white light and blue light reared monkeys for all stimulus energies. ISCEV standard light- and dark-adapted a- and b-wave amplitudes were not significantly different between groups (P > 0.05 for all). There were no significant differences in a- and b-wave implicit times between groups for all ISCEV standard stimuli (P > 0.05 for all). PhNR amplitudes of young monkeys were significantly smaller compared to adult monkeys for all stimulus energies (P < 0.05 for all). There were no significant differences in a-wave (P = 0.19) and b-wave (P = 0.17) amplitudes between young and adult white light reared monkeys. Long-term exposure to narrowband blue light did not affect photopic or scotopic ERG responses in young monkeys. Findings suggest that exposure to 12h of daily blue light for approximately 10months does not result in altered retinal function.

Alterations of color vision and pupillary light responses in age-related macular degeneration.

Age-related macular degeneration (AMD) is the leading cause of irreversible central vision loss in developed countries and one of the leading causes of blindness. In this work, we evaluated color vision and the pupil light reflex (PLR) to assess visual function in patients with early and neovascular AMD (NVAMD) compared with the control group. We recruited 34 early patients with dry AMD and classified them into two groups following AREDS: 13 patients with NVAMD and 24 healthy controls. Controls and patients with early dry AMD had visual acuity (VA) best or equal to 20/25 (0.098 logMAR). Color vision was assessed in controls and patients with early dry AMD using the Cambridge Color Test (CCT) 2.0 through the Trivector protocol. The PLR was evaluated using a Ganzfeld, controlled by the RETI-port system. The stimuli consisted of 1s blue (470 nm) and red (631 nm) light flashes presented alternately at 2-min intervals. To assess the cone contribution, we used a red flash at 2.4 log cd.m-2, with a blue background at 0.78 log cd.m-2. For rods, we used 470-nm flashes at -3 log cd.m-2, and for the melanopsin function of ipRGCs, we used 470 nm at 2.4 log cd.m-2. Patients with early dry AMD had reduced color discrimination in all three axes: protan (p = 0.0087), deutan (p = 0.0180), and tritan (p = 0.0095) when compared with the control group. The PLR has also been affected in patients with early dry AMD and patients with NVAMD. The amplitude for the melanopsin-driven response was smaller in patients with early dry AMD (p = 0.0485) and NVAMD (p = 0.0035) than in the control group. The melanopsin function was lower in patients with NVAMD (p = 0.0290) than the control group. For the rod-driven response, the latency was lower in the NVAMD group (p = 0.0041) than in the control group. No changes were found in cone-driven responses between the control and AMD groups. Patients with early dry AMD present diffusely acquired color vision alteration detected by CCT. Rods and melanopsin contributions for PLR are affected in NVAMD. The CCT and the PLR may be considered sensitive tests to evaluate and monitor functional changes in patients with AMD.

Pre-stimulus bioelectrical activity in light-adapted ERG under blue versus white background.

To compare the baseline signal between two conditions used to generate the photopic negative response (PhNR) of the full-field electroretinogram (ERG): red flash on a blue background (RoB) and white flash on a white background (LA3). The secondary purpose is to identify how the level of pre-stimulus signal affects obtaining an unambiguous PhNR component. A retrospective chart review was conducted on four cohorts of patients undergoing routine ERG testing. In each group, LA3 was recorded the same way while RoB was generated differently using various luminances of red and blue light. The background bioelectrical activity 30ms before the flash was extracted, and the root mean square (RMS) of the signal was calculated and compared between RoB and LA3 using Wilcoxon test. Pre-stimulus noise was significantly higher under RoB stimulation versus LA3 in all four conditions for both right and left eyes (ratio RoB/LA3 RMS 1.70 and 1.57 respectively, p<0.033). There was also no significant difference between the RMS of either LA3 or RoB across protocols, indicating that the baseline noise across cohorts were comparable. Additionally, pre-stimulus noise was higher in signals where PhNR was not clearly identifiable as an ERG component versus signals with the presence of unambiguous PhNR component under RoB in all four groups for both eyes (p<0.05), whereas the difference under LA3 was less pronounced. Our study suggests that LA3 produces less background bioelectrical activity, likely due to decreased facial muscle activity. As it seems that the pre-stimulus signal level affects PhNR recordability, LA3 may also produce a better-quality signal compared to RoB. Therefore, until conditions for a comparable bioelectrical activity under RoB are established, we believe that LA3 should be considered at least as a supplementary method to evaluate retinal ganglion cell function by ERG.

Little Amal’s New York Journey: The Big Puppet in the Big Apple

Little Amal’s New York Journey: The Big Puppet in the Big Apple

The red flashes of folkmarketing. Coca Cola's strategy with the Bolivian salteña

The red flashes of folkmarketing. Coca Cola's strategy with the Bolivian salteña

Use of extended protocols with nonstandard stimuli to characterize rod and cone contributions to the canine electroretinogram.

In this study, we assessed several extended electroretinographic protocols using nonstandard stimuli. Our aim was to separate and quantify the contributions of different populations of retinal cells to the overall response, both to assess normal function and characterize dogs with inherited retinal disease. We investigated three different protocols for measuring the full-field flash electroretinogram-(1) chromatic dark-adapted red and blue flashes, (2) increasing luminance blue-background, (3) flicker with fixed frequency and increasing luminance, and flicker with increasing frequency at a fixed luminance-to assess rod and cone contributions to electroretinograms recorded in phenotypically normal control dogs and dogs lacking rod function. Temporal separation of the rod- and cone-driven responses is possible in the fully dark-adapted eye using dim red flashes. A- and b-wave amplitudes decrease at different rates with increasing background luminance in control dogs. Flicker responses elicited with extended flicker protocols are well fit with mathematical models in control dogs. Dogs lacking rod function demonstrated larger amplitude dark-adapted compared to light-adapted flicker responses. Using extended protocols of the full-field electroretinogram provides additional characterization of the health and function of different populations of cells in the normal retina and enables quantifiable comparison between phenotypically normal dogs and those with retinal disease.

Notes on Contributors

Notes on Contributors

Influence of pre‐adaptation time to background illumination on photopic negative response of the full‐field electroretinogram

AbstractPurposeThe photopic negative response (PhNR) is a negative wave (latency ~70ms) of the full‐field electroretinogram (ERG) which represents ganglion cell activity. The amplitude is most distinctive for a red stimulus on a blue background. In the literature different pre‐adaptation times (range from few seconds to 10min) to the blue background can be found. The aim of the study presented here was to verify whether the pre‐adaptation time to the blue background has an influence on the PhNR wave.MethodsIn total 12 subjects (25.4±2.0years, 4m, 8f) participated in the study. For visual stimulation, a full‐field stimulator with a red flash (wavelength: 625nm, flash strength: 1.5cds/m², duration: ≤ 5ms, inter‐flash interval: 1s) on blue background (wavelength: 455nm, luminance: 10cd/m²) was used. For ERG recording, Ag/AgCl ring‐shaped skin‐electrodes were placed at the lower eyelid, the ipsilateral earlobe, and the forehead. The subjects were light adapted before all measurements. Each ERG measurement consisted of a pre‐adaptation time (15s/1/2/5/10min, randomized order) followed by an ERG measurement, which includes 20 artifact‐free sweeps. The PhNR wave was defined as the minimum after the b‐wave in the latency range from 60 to 80ms and was measured from the baseline (BT) and from the b‐wave peak (PT). For statistical analysis, the Friedman‐test was applied between the pre‐adaptation times for both measured amplitudes and the latency (α=0.05).ResultsThe PhNR could be measured and analyzed from all subjects. The Friedman‐test showed no significant difference between the pre‐adaption times for both amplitudes and the latency (*p ≤ 0.0167; pBT‐amplitude = 0.281, pPT‐amplitude = 0.797, platency = 0.448).ConclusionsWe found no influence of the pre‐adaption time to the blue background on the PhNR amplitude and latency. Therefore, for future work only a short pre‐adaptation time of a few seconds is sufficient for a stable PhNR wave measurement for light adapted subjects.

Impaired Ganglion Cell Function Objectively Assessed by the Photopic Negative Response in Affected and Asymptomatic Members From Brazilian Families With Leber's Hereditary Optic Neuropathy.

Purpose: The photopic negative response (PhNR) is an electrophysiological method that provides retinal ganglion cell function assessment using full-field stimulation that does not require clear optics or refractive correction. The purpose of this study was to assess ganglion cell function by PhNR in affected and asymptomatic carriers from Brazilian families with LHON.Methods: Individuals either under suspicion or previously diagnosed with LHON and their family members were invited to participate in this cross-sectional study. Screening for the most frequent LHON mtDNA mutations was performed. Visual acuity, color discrimination, visual fields, pattern-reversal visual evoked potentials (PRVEP), full-field electroretinography and PhNR were tested. A control group of healthy subjects was included. Full-field ERG PhNR were recorded using red (640 nm) flashes at 1 cd.s/m2, on blue (470 nm) rod saturating background. PhNR amplitude (μV) was measured using baseline-to-trough (BT). Optical coherence tomography scans of both the retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) were measured. PhNR amplitudes among affected, carriers and controls were compared by Kruskal-Wallis test followed by post-hoc Dunn test. The associations between PhNR amplitude and OCT parameters were analyzed by Spearman rank correlation.Results: Participants were 24 LHON affected patients (23 males, mean age=30.5 ± 11.4 yrs) from 19 families with the following genotype: m.11778G>A [N = 15 (62%), 14 males]; m.14484T>C [N = 5 (21%), all males] and m.3460G>A [N = 4 (17%), all males] and 14 carriers [13 females, mean age: 43.2 ± 13.3 yrs; m.11778G>A (N = 11); m.3460G>A (N = 2) and m.14484T>C (N = 1)]. Controls were eight females and seven males (mean age: 32.6 ± 11.5 yrs). PhNR amplitudes were significantly reduced (p = 0.0001) in LHON affected (−5.96 ± 3.37 μV) compared to carriers (−16.53 ± 3.40 μV) and controls (−23.91 ± 4.83; p < 0.0001) and in carriers compared to controls (p = 0.01). A significant negative correlation was found between PhNR amplitude and total macular ganglion cell thickness (r = −0.62, p < 0.05). Severe abnormalities in color discrimination, visual fields and PRVEPs were found in affected and subclinical abnormalities in carriers.Conclusions: In this cohort of Brazilian families with LHON the photopic negative response was severely reduced in affected patients and mildly reduced in asymptomatic carriers suggesting possible subclinical abnormalities in the latter. These findings were similar among pathogenic mutations.

Electroretinographic study of the magnetic compass in European robins.

Migratory birds are known to be sensitive to external magnetic field (MF). Much indirect evidence suggests that the avian magnetic compass is localized in the retina. Previously, we showed that changes in the MF direction could modulate retinal responses in pigeons. In the present study, we performed similar experiments using the traditional model animal to study the magnetic compass, European robins. The photoresponses of isolated retina were recorded using ex vivo electroretinography (ERG). Blue- and red-light stimuli were applied under an MF with the natural intensity and two MF directions, when the angle between the plane of the retina and the field lines was 0° and 90°, respectively. The results were separately analysed for four quadrants of the retina. A comparison of the amplitudes of the a- and b-waves of the ERG responses to blue stimuli under the two MF directions revealed a small but significant difference in a- but not b-waves, and in only one (nasal) quadrant of the retina. The amplitudes of both the a- and b-waves of the ERG responses to red stimuli did not show significant effects of the MF direction. Thus, changes in the external MF modulate the European robin retinal responses to blue flashes, but not to red flashes. This result is in a good agreement with behavioural data showing the successful orientation of birds in an MF under blue, but not under red illumination.

First record of Common Red Flash, Rapala iarbus from the state of Rajasthan, India

In this paper, we report a first record of Common Red Flash, Rapala iarbus butterfly from the state of Rajasthan. The specimen was observed in the residential area, located at the outskirt of the Bhilwara city, Rajasthan, India.

Investigation of light-induced lacrimation and pupillary responses in episodic migraine.

The purpose of this pilot study was to investigate the light-induced pupillary and lacrimation responses mediated by intrinsically photosensitive retinal ganglion cells (ipRGCs) in migraine. Ten participants with episodic migraine and normal tear production, as well as eleven visually normal controls participated in this study. Following an initial baseline trial (no light flash), participants received seven incremental and alternating red and blue light flashes. Pupillometry recording of the left eye and a 1-min anesthetized Schirmer’s test of the right eye (using 0.5% proparacaine) were performed simultaneously. Intrinsic and extrinsic ipRGC photoactivities did not differ between migraine participants and controls across all intensities and wavelengths. Migraine participants, however, had significantly lower lacrimation than controls following the highest blue intensity. A positive correlation was found between melanopsin-driven post-illumination pupillary responses and lacrimation following blue stimulation in both groups. Our results show that participants with self-reported photophobia have normal ipRGC-driven responses, suggesting that photophobia and pupillary function may be mediated by distinct ipRGC circuits. The positive correlation between melanopsin-driven pupillary responses and light-induced lacrimation suggests the afferent arm of the light-induced lacrimation reflex is melanopsin-mediated and functions normally in migraine. Lastly, the reduced melanopsin-mediated lacrimation at the highest stimulus suggests the efferent arm of the lacrimation reflex is attenuated under certain conditions, which may be a harbinger of dry eye in migraine.

Relationship between stimulus size and different components of the electroretinogram (ERG) elicited by flashed stimuli.

To investigate how light stimulus conditions of varying spatial sizes affect components of the flash and long-flash electroretinogram (ERG) in normal subjects. Three stimulus conditions were generated by a Ganzfeld stimulator: a white flash on white background (WoW), a red flash on a blue background (RoB) and an L+M-cone isolating on-off (long flash) stimulus (Cone Iso). ERGs were recorded from six subjects (5M, 1 F) with DTL electrodes to full-field (FF), 70°, 60°, 50°, 40°, 30° and 20° diameter circular stimuli. Amplitudes and peak times for a-, b-, d- and i-wave, and PhNR were examined. PhNR amplitudes were estimated in two different ways: from baseline (fB) and from preceding b-wave peak (fP). With decreasing stimulus size, amplitudes for all ERG waveform components attenuated and peak times increased, although the effect varied across different components. An exponential fit described the relationship between amplitudes and size of stimulated retinal area well for most components and conditions (R2= 0.75-0.99), except for PhNR(fB) (R2= - 0.16-0.88). For peak times, an exponential decay function also fitted the data well (R2= 0.81-0.97), except in a few cases where the exponential constant was too small and a linear regression function was applied instead (a-wave Cone Iso, b- and i-wave WoW). The exponential constants for RoB amplitudes (b-wave, PhNR(fB), PhNR(fP)) were larger compared to their counterparts under WoW (p < 0.05), while there was no difference between the constants for a-wave amplitudes and peak times and for PhNR peak times. The exponential constants of amplitudes vs. area under WoW and Cone Iso were remarkably similar, while under RoB PhNR(fB) showed larger constants compared to either a- or b-wave (p < 0.05). ERG components change in a predictable way with stimulus size and spectral characteristics of the stimulus under these conditions. This predictability could allow a modified version of these sets of stimuli to be tested for clinical applicability.

Рhotopic Negative Response for Testing the Function of Inner Retina: Registration Requirements and Comparison in the Eyes with Natural Pupil Width and in Conditions of Drug Mydriasis

Purpose: To evaluate the possibility of registration of the photopic negative response (PhNR) without pupil dilatation in healthy individuals to determine the dysfunction of neurons of the inner retina.Methods: 12 healthy persons (23 eyes) aged 24 to 40 years were examined. Refraction anomalies did not exceed 0.5 diopters. A PhNR was evaluated in photopic ERGs recorded on a blue background with red flashes of four intensities (0.375, 0.75, 1.5, 3.0 cd·s/m2) using the RETIport/scan21 (Roland Consult). First, ERG was recorded with the natural pupil (3.5 ± 0.2 mm). Then, the recording was repeated after drug mydriasis (average pupil size 8.7 ± 0.1 mm).Results. In eyes with natural pupil width, in comparison with drug mydriasis, PhNR amplitudes in responses to weakest stimuli (0.375 cd·s/m2) were significantly reduced. The effect of pupil size on the PhNR amplitude from a baseline was virtually absent in responses to higher strength flashes. This phenomenon can be associated with an irregular distribution of light over the retina with small pupil size, the effect of which is maximal in responses to weak flashes. For the maximal brightness stimuli (3.0 cd·s/m2), differences were found between groups of non-dilated and dilated pupils in the amplitudes of the b-wave and PhNR from the b-peak, which may reflect a decrease in the number of stimulated photoreceptors during ganzfeld stimulation when the pupil is not dilated.Conclusion. The effect of pupil size on the parameters of the PhNR was most significant in the ERG with minimal flash strength and it decreases in responses to flashes of higher brightness. If it is necessary to record the ERG without drug mydriasis, especially in screening studies, it is recommended to limit the protocol to estimate the PhNR from a baseline in responses to maximal flashes, and use the relative parameter — the amplitude ratio of PhNR/b. Keywords: photopic negative response, electroretinography, pupil width

Morphological, cytological, and pigment analysis of leaf color variants regenerated from long-term subcultured caladium callus

Cultivated caladiums (Caladium × hortulanum Birdsey) are popular ornamental plants. Although somaclonal variation occurs frequently in caladium during tissue culture, little research has been conducted on obtaining and detecting variants from long-term callus cultures. Herein, plants were regenerated from ‘Red Flash’ caladium calluses subcultured for approximately 40 mo, and 116 out of 520 established plants were grouped into 14 somaclonal variation types based on their morphological differences. Nuclear DNA content of six types (SVT1, SVT2, SVT4, SVT5, SVT8, and SVT10) varied from − 1.08% to 0.33% compared with the wild type, and these variants shared a similar chromosome number to the wild caladium (2n = 2x = 30). Three types (SVT3, SVT7, and SVT9) containing 2.82 to 5.42% less nuclear DNA content was the result of losing one or two chromosomes, and one type (SVT6) with significantly lower cellular DNA content was due to losing four chromosomes. Four types (SVT11–SVT14) contained 85.16 to 101.52% more DNA content and the SVT12 and the SVT13 had a double number of chromosomes (2n = 4x = 60), while the SVT11 and SVT14 had four more chromosomes and six less chromosomes as compared with a typical tetraploid, respectively. Correlation analysis suggested that leaf thickness, leaf index, and stomatal characteristics could be used as indicators of plant ploidy in caladium. A wide variation of pigment content was found among the variation types, and the content of chlorophyll, flavonoid, and anthocyanin had a significant positive correlation with the color parameters a* and b*. Leaf color variants created by prolonged in vitro callus cultures might hold great promise for caladium breeding.