White Light Stimulus Research Articles

Regional variations distinguish auditory from visual evoked potentials in healthy 4 week old piglets

Objective. Evoked potentials (EP), measured using electroencephalographic (EEG) recordings provide an opportunity to monitor cognitive dysfunctions after neurological diseases or traumatic brain injury (TBI). The 4 week old piglet is an established model of paediatric TBI; therefore, healthy piglets were studied to establish feasibility of obtaining responses to auditory and visual stimuli. A secondary aim was to input the EEG data into a piglet computational model to localize the brain sources related to processing. We tested the hypotheses: (1) visual, auditory-standard, and auditory-target stimuli elicit responses, (2) there is an effect of stimulus type, day tested, and electrode region on EPs from EEG, (3) there is an effect of stimulus type, day tested, and brain region on localized sources from a computational model. Approach. Eleven 4 week old female piglets were fitted with a 32-electrode net and presented with a simple white light stimulus and an auditory oddball click train (70 standard; 30 target tones). Main results. N1 and P2 amplitudes were consistently observed for all stimulus types. Significant interaction effects between brain region and stimulus for EP and current density demonstrate that cognitive responses are specific to each modality with auditory localizing to the temporal region and visual to the occipital regions. There was a day effect where larger responses were found on the first day than day 2 and 3 and may be due to the novelty of the stimulus on the first day. Visual stimuli had larger P1 amplitudes and earlier latencies (P1, N1) than auditory which coincides with current density results at 50 ms where larger activations were observed for visual. At 85 ms, auditory had significantly larger current densities coincident with larger and longer N1 amplitudes and latencies than visual. Significance. Auditory and visual processing were successfully and consistently obtained in a porcine model and can be evaluated as a diagnostic assessment for TBI.

Photoswitchable lanthanide-doped core-multishell nanoparticles for tunable triple-mode information encryption and dynamic anti-counterfeiting patterns

Photoresponsive luminescent materials with high-capacity information storage and multilevel anti-counterfeiting capability are attracting much interest in many fields including information encryption and anti-counterfeiting. Herein, a class of novel photoswitchable upconversion luminescent nanoparticles (PUCNPs) with core-multishell structure that shows switchable dual-colored emission is described. The PUCNPs is successively built up from lanthanide-doped NaYF4 nanoparticles and a photochromic spiropyrane (SP) monomer by grafting of poly(glycidyl methacrylate-co-SPMA) on the nanoparticles via surface reversible addition-fragmentation chain transfer (RAFT) polymerization. The as-prepared PUCNPs with triple-mode optical features displayed green upconversion luminescence under a 980 nm laser, red downconervsion fluorescence and purple color under a 365 nm UV light irradiation and turning off, respectively. Furthermore, they enable dynamic reversible changes in color between colorless and purple states with 365 nm UV and white light stimuli. Their potential in complex information encryption and dynamic anti-counterfeiting patterns is described and its great potential in data storage, and rewritable optical materials is foreseen.

Pupillary Light Reflex Metrics Differ in Adolescents with Acute Concussion VS. Persistent Post-Concussion Symptoms

Background: A potential objective measure that may assist in identifying vision disorders after concussion is the pupillary light reflex (PLR), which is under autonomic control and contributes to normal convergence and accommodative function which is altered after concussion. This study sought to compare pupillometry measures in adolescents with concussion initially presenting for care in the early acute time frame (≤ 2 weeks post-concussion) to those presenting in the later acute time frame (4 ± 1 weeks). Hypothesis: To determine whether PLR metrics are similar or different between athletes with concussion presenting earlier (≤ 2 weeks post-concussion) for care vs. those presenting later for care (4 ± 1 weeks). Methods: Athletes, ages 12-18 years, with a diagnosis of sport-related concussion (n = 110) were recruited. 89 concussed subjects had their PLR assessment performed at an early acute time point ≤ 2 weeks after concussion, while 21 concussed subjects had their first assessment at a later acute time point (4 week±1 week). Pupillary dynamics were measured in response to a brief, step-input, white light stimulus (154 ms duration; 180 micro watts power) via a Neuroptics PLR-3000 hand-held, infrared, automated, monocular pupillometer (Neuroptics, Irvine, CA). The means of the PLR metrics were compared between groups with one-way Student’s t test. Bonferroni correction was applied. Results: The baseline pupil diameter (mean ± SD) was significantly larger (p<0.05) for the subjects seen later 4 ± 1 week (5.09 mm ± 0.63) as compared to the cohort of subjects who presented earlier within 2 weeks after injury (4.72 ± 0.79mm). Average constriction velocity ACV for the later-presenting cohort (3.35±0.45 mm/s) was significantly faster compared to the early-presenting cohort (3.04±0.59 mm/s). Similarly, maximum constriction velocity for the groups were significantly different (early 4.82±0.90 versus late 5.31±0.70 mm/s), even after Bonferroni correction (p<0.05), with alpha of 0.025. All the other pupillometric parameters were not different from each other. Conclusion: When comparing adolescents with concussion presenting early in the acute phase ≤ 2 weeks after concussion to those presenting later in the acute timeframe to care 4±1 weeks, those presenting later demonstrate enhancement of certain PLR metrics, namely larger baseline pupil diameter and faster average constriction velocity (ACV) and maximum constriction velocity (MCV). Differences in these PLR metrics in those presenting later in the acute timeframe may represent findings in those who are more likely to have persisting post-concussion symptoms, potentially shedding light on pathophysiological underpinnings of lingering symptoms.

Fast Optical‐Thermal Responsive Intelligent Glass Realized by Hydrated Poly(N‐Isopropylacrylamide) Film

AbstractGlass is widely applied in fields of architecture, automobiles, optics and instruments due to its light transmission, wind resistance, sound and heat insulation. However, the light transmittance of traditional glass cannot change after the glass is formed, which limits the practicability of glass. In this study, an intelligent glass that can quickly and freely switch between transparency and opacity based on an optical‐thermal responsive hydrated poly(N‐isopropylacrylamide) film triggered by white light, infrared light, and direct thermal stimuli is developed. The fastest response time is ≈21 s under white light or 5 s by hand touch. A fatigue test of 250 cycles showed no obvious performance degradation. The transmittance of the intelligent glass changed reversibly between 88.5%–93.2% (transparent) and 25.5%–41.6% (opaque). The optical‐thermal response of the intelligent glass is attributed to the reversible phase transition of the hydrated poly(N‐isopropylacrylamide) film. This intelligent glass not only has obvious advantages in energy savings and emission reduction but also may be very useful for privacy protection, for example, in car windows, house windows, and office windows.

Natural DNA assisted white light generation and stimuli responsive colour tuning

The unique structure of a natural nucleic acid, calf thymus DNA, which can provide an appropriate scaffold for an efficient cascaded energy transfer among organic chromophores, has been used for the generation of bright and pure white light on UV light excitation. Two most commonly used DNA stains, 4′,6-diamidino-2-phenylindole (DAPI) and ethidium bromide (EB) have been used as a part of the donor-acceptor pairs. We have judiciously selected 10-anthracene-10-yl-3-methylbenzothiazol-3-ium chloride (AnMBTZ), an ultrafast molecular rotor, to act as a bridge between DNA bound DAPI and EB for the cascaded flow of energy. The unique molecular rotor properties of AnMBTZ and its exceptional binding ability with natural DNA help to form a distinct tri-chromophoric system in DNA template which can produce bright and pure white light on UV excitation. Detailed flow of energy from photoexcited DAPI to EB via AnMBTZ has been explored using steady state and time-resolved emission spectroscopy. Further, unique binding nature of AnMBTZ with DNA molecules has been used to modulate the colour of the emission from the present tri-chromophoric system by external stimuli, like salt and temperature. Such unique stimuli responsive multi-chromophoric system in a bio-template has great potential for different lightening applications.

156 Evening Light-Induced Circadian Phase Shift in Preschool-Aged Children

Abstract Introduction In adults, exposure to light at night delays the timing of the circadian clock in a dose-dependent manner with intensity. Although children’s melatonin levels are highly suppressed by evening bright light, the sensitivity of young children’s circadian timing to evening light is unknown. This research aimed to establish an illuminance response curve for phase delay in preschool children as a result of exposure to varying light intensities in the hour before bedtime. Methods Healthy children (n=36, 3.0 – 4.9 years, 39% males), participated in a 10-day protocol. For 7 days, children followed a strict parent-selected sleep schedule. On Days 8-10, an in-home dim-light assessment was performed. On Day 8, dim light melatonin onset (DLMO) was measured through saliva samples collected in 20-30-min intervals throughout the evening until 1-h past habitual bedtime. On Day 9, children were exposed to a white light stimulus (semi-randomly assigned from 5lx to 5000lx) for 1-h before their habitual bedtime, and saliva was collected before, during, and after the exposure. On Day 10, children provided saliva samples in the evening for 2.5-h past bedtime for a final DLMO assessment. Phase angle of entrainment (habitual bedtime – DLMObaseline) and circadian phase delay (DLMOfinal – DLMObaseline) were computed. Results Final DLMO (Day 10) shifted between -8 and 123 minutes (M = 56.1 +/- 33.6 min; negative value = phase advance, positive value = phase delay) compared with DLMO at baseline (Day 8). Raw phase shift did not demonstrate a dose-dependent relationship with light intensity. Rather, we observed a robust phase delay across all intensities. Conclusion These data suggest preschoolers’ circadian clocks are immensely sensitive to a large range of light intensities, which may be mechanistically influenced by less mature ophthalmologic features (e.g. clearer lenses, larger pupils). With young children’s ever-growing use of light-emitting devices and evening exposure to artificial lighting, as well as the prevalence of behavioral sleep problems, these findings may inform recommendations for parents on the effects of evening light exposure on sleep timing in early childhood. Support (if any) This research was supported with funds from the Eunice Kennedy Shriver National Institute of Child Health & Human Development (R01-HD087707).

Cataract type and pupillary response to blue and white light stimuli

We evaluated the pupil reaction to blue and white light stimulation in 70 eyes with cataract and in 38 eyes with a selective blue-light filtering intra-ocular lens. The diameter of the pupil before stimulation was set as baseline (BPD) and, after a stimulus duration of 1 s, the post-illumination pupillary response (PIPR) was measured using an electronic pupillometer. The BPD showed no significant difference among three grades of nuclear sclerosis (NS). In contrast, the PIPRs differed significantly among the NS grades eyes including with and without subcapsular cataract (SC) and IOL eyes for white light (p < 0.05, Kruskal–Wallis test), but not for blue light. Subcapsular opacity did not affect the BPD or PIPR in all cataract grades for either light stimulus. The tendency of larger PIPR in the pseudophakic eyes than the cataract eyes for both lights, however significant difference was found only for white light (p < 0.05 for white light, p > 0.05 for blue light). Our study demonstrates retention of the PIPR for blue light, but not for white light in cataract eyes. We also confirmed that the pupillary response in pseudohakic eyes with a selective blue light-filtering intra ocular lens was greater than that in cataractous eyes for white light.

The use Of Pupillary Light Reflex in Concussed Athletes

Background:Despite advancements, concussion diagnosis remains reliant on subjective symptom report and clinical assessments. Visual deficits and autonomic dysfunction have been described following concussion. Testing of the pupillary light reflex (PLR) is a simple, portable, non-invasive, and objective means of quantifying pupillary function.Purpose:The aim of this study was to objectively evaluate pupillary responses to a light stimulus in concussed adolescent athletes and to determine whether clinical assessments correlated with PLR responses after a diagnosed concussion when compared to pre-injury responses.Methods:In this prospective cohort study, PLR and clinical measures [PCSI and/or SCAT symptom scales, near point of convergence (NPC) and accommodation amplitude (AA) of both eyes] were assessed in 93 (45 female), non-concussed adolescent athletes (ages 14-18) during their pre-season. PLR was obtained in response to a brief white light stimulus using a hand-held pupillometer. During each assessment, three monocular trials were performed in each eye alternatively, with subsequent averaged responses for each eye. Seven athletes (ages 14-17) sustained a concussion and had post-injury assessments of PLR and clinical measures completed longitudinally through recovery.Results:All seven concussed athletes completed PLR and clinical assessments at least once post-injury (mean initial day of evaluation = 6 days post injury). Six out of the seven concussed athletes demonstrated an increase in steady state diameter of 24% (median 18%), minimum pupil diameter of 17% (median 11%) and a maximum constriction velocity of 28% (median 33%) following concussion which decreased over the course of recovery, returning to pre-injury or below pre-injury measurements. Six of seven of the concussed athletes completed NPC and AA assessments at both pre-season and post-injury timepoints. In contrast to the PLR findings, both NPC and AA measures were normal at post-injury assessments. Reported symptom scores improved throughout recovery, correlating with PLR response recovery, with both returning to pre-injury measurements.Conclusion:Pupil responsivity was found to be significantly enhanced after concussion compared to pre-injury measurements, waning over time during recovery, following a similar trajectory as symptom burden. NPC and AA, which have autonomic contributions and are clinical measures, were normal pre- and post-injury and did not differentiate the concussed state from the uninjured state in our series. Our preliminary results demonstrate that dynamic PLR responses may detect acute autonomic deficits that are not evident via clinical assessments. Further investigation of its potential utility as sensitive and objective biomarker in concussion diagnosis, management and sports clearance is warranted.

Relationship between Macular Vessel Density and Focal Electroretinograms in Early Normal Tension Glaucoma

ABSTRACTPurpose: To evaluate the relationship between the macular vessel density and photopic negative response (PhNR) amplitude of focal electroretinograms (ERGs) in patients with early-stage normal tension glaucoma (NTG).Materials and Methods: This prospective cross-sectional study included a total of 42 subjects with early-stage NTG. Optical coherence tomography angiography was used to measure macular vessel density, and focal ERGs were elicited by a white light stimulus (30 cd/m2) with background light (1.5 cd/m2). The amplitude of the PhNR was measured from the peak of the b-wave to the PhNR trough. Mean visual field sensitivity was measured by the Humphrey Field Analyzer (HFA) program central 10–2. Spearman’s coefficients were used to evaluate the correlation between the macular vessel density, PhNR amplitude, mean deviation (MD) of the HFA 10–2, retinal nerve fiber layer (RNFL) thickness, and ganglion cell complex (GCC) thickness measured by spectral domain-optical coherence tomography.Results: The mean MD of the HFA 10–2 was −2.0 ± 3.2 dB. The PhNR amplitude significantly correlated with the macular vessel density (r = 0.420, P = 0.006), but not with the MD, GCC thickness, or RNFL thickness. The macular vessel density significantly correlated with the MD (r = 0.364, P = 0.018) and RNFL thickness (r = 0.369, P = 0.016), but not with GCC thickness (r = 0.266, P = 0.089).Conclusions: Macular vessel density significantly correlated with PhNR amplitude in patients with early-stage NTG, suggesting that microvascular alterations are associated with functional changes recorded by focal ERG in very early-stage glaucoma.

THE UTILITY OF PUPILLARY LIGHT REFLEX AS AN OBJECTIVE BIOMARKER OF ACUTE CONCUSSION IN THE ADOLESCENT ATHLETE

Background: Visual deficits and autonomic dysfunction have been well recognized following pediatric concussion. Testing of the pupillary light reflex (PLR) is a simple, non-invasive, and objective approach to examine the autonomic nervous system by accessing the brain pathways. The aim of this study was to objectively evaluate adolescent pupillary responses to a light stimulus after a physician-diagnosed concussion and compare them to baseline responses. Methods: In this prospective cohort study, PLR was assessed in 135 adolescent athletes (ages 14-18) during their sport pre-season. All of the athletes were not recovering from a concussion at the time of their baseline assessment. Within this cohort, seven athletes (ages 14-17) sustained a concussion during their sport season and had longitudinal post-injury assessments of PLR through their recovery. The PLR was obtained in response to a brief step-input (0.8 seconds) white light stimulus using a hand-held pupillometer (stimulus recording duration= 5 seconds, light intensity= 150 lux). Pre-set and automated device-generated parameters used for analysis include the minimum and maximum pupil diameter, response amplitude and latency, mean constriction and dilation velocities and the maximum constriction velocity of the eye in response to a light stimulus. During each assessment, three monocular trials were performed in each eye alternatively, and the responses for each eye were subsequently averaged. Results: Six out of the seven concussed adolescents showed response enhancement of about 20% (IQR 11-33%). Enhancement was noted in the steady state diameter with a mean of 24% (median 18%), minimum pupil diameter mean of 17% (median 11%) and maximum constriction velocity mean of 28% (median 33%) following concussion, which decreased during the recovery process (days to weeks post-injury) to pre-injury or below initial pre-injury baseline measurements. Pupillary responsivity was found to be significantly enhanced after concussion compared to baseline measurements, waning over time. Maximum constriction velocity better highlighted the enhancement compared to the baseline pupil diameter. Conclusions/Significance: Pupil responsivity was found to be significantly enhanced after concussion compared to baseline measurements which waned over time during recovery. Assessment of dynamic PLR responses has potential utility as an objective biomarker to aid in concussion diagnosis on the sidelines or in the office, allowing physicians to quantify function (and dysfunction) of the autonomic nervous system under parasympathetic and sympathetic control after concussion.

One month of hyperglycemia alters spectral responses of the zebrafish photopic electroretinogram.

ABSTRACTProlonged hyperglycemia can alter retinal function, ultimately resulting in blindness. Adult zebrafish adults exposed to alternating conditions of 2% glucose/0% glucose display a 3× increase in blood sugar levels. After 4 weeks of treatment, electroretinograms (ERGs) were recorded from isolated, perfused, in vitro eyecups. Control animals were exposed to alternating 2% mannitol/0% mannitol (osmotic control) or to alternating water (0% glucose/0% glucose; handling control). Two types of ERGs were recorded: (1) native ERGs measured using white-light stimuli and medium without synaptic blockers; and (2) spectral ERGs measured with an AMPA/kainate receptor antagonist, isolating photoreceptor-to-ON-bipolar-cell synapses, and a spectral protocol that separated red (R), green (G), blue (B) and UV cone signals. Retinas were evaluated for changes in layer thickness and for the inflammatory markers GFAP and Nf-κB (RelA or p65). In native ERGs, hyperglycemic b- and d-waves were lower in amplitude than the b- and d-waves of mannitol controls. Alteration of waveshape became severe, with b-waves becoming more transient and ERG responses showing more PIII-like (a-wave) characteristics. For spectral ERGs, waveshape appeared similar in all treatment groups. However, a1- and b2-wave implicit times were significantly longer, and amplitudes were significantly reduced, in response to hyperglycemic treatment, owing to the functional reduction in signals from R, G and B cones. Nf-κB increased significantly in hyperglycemic retinas, but the increase in GFAP was not significant and retinal layer thickness was unaffected. Thus, prolonged hyperglycemia triggers an inflammatory response and functional deficits localized to specific cone types, indicating the rapid onset of neural complications in the zebrafish model of diabetic retinopathy.

A Novel Visual Psychometric Test for Light-Induced Discomfort Using Red and Blue Light Stimuli Under Binocular and Monocular Viewing Conditions

To develop an objective psychophysical method to quantify light-induced visual discomfort, and to measure the effects of viewing condition and stimulus wavelength. Eleven visually normal subjects participated in the study. Their pupils were dilated (2.5% phenylephrine) before the experiment. A Ganzfeld system presented either red (1.5, 19.1, 38.2, 57.3, 76.3, 152.7, 305.3 cd/m2) or blue (1.4, 7.1, 14.3, 28.6, 42.9, 57.1, 71.4 cd/m2) randomized light intensities (1 s each) in four blocks. Constant white-light stimuli (3 cd/m2, 4 s duration) were interleaved with the chromatic trials. Participants reported each stimulus as either "uncomfortably bright" or "not uncomfortably bright." The experiment was done binocularly and monocularly in separate sessions, and the order of color/viewing condition sequence was randomized across participants. The proportion of "uncomfortable" responses was used to generate individual psychometric functions, from which 50% discomfort thresholds were calculated. Light-induced discomfort was higher under blue compared with red light stimulation, both during binocular (t(10) = 3.58, P < 0.01) and monocular viewing (t(10) = 3.15, P = 0.01). There was also a significant difference in discomfort between viewing conditions, with binocular viewing inducing more discomfort than monocular viewing for blue (P < 0.001), but not for red light stimulation. The light-induced discomfort characteristics reported here are consistent with features of the melanopsin-containing intrinsically photosensitive retinal ganglion cell light irradiance pathway, which may mediate photophobia, a prominent feature in many clinical disorders. This is the first psychometric assessment designed around melanopsin spectral properties that can be customized further to assess photophobia in different clinical populations.

Influence of refractive error on pupillary dynamics in the normal and mild traumatic brain injury (mTBI) populations

PurposeThere have been several studies investigating static, baseline pupil diameter in visually-normal individuals across refractive error. However, none have assessed the dynamic pupillary light reflex (PLR). In the present study, both static and dynamic pupillary parameters of the PLR were assessed in both the visually-normal (VN) and the mild traumatic brain injury (mTBI) populations and compared as a function of refractive error. MethodsThe VN population comprised 40 adults (22–56 years of age), while the mTBI population comprised 32 adults (21–60 years of age) over a range of refractive errors (−9.00D to +1.25D). Seven pupillary parameters (baseline static diameter, latency, amplitude, and peak and average constriction and dilation velocities) were assessed and compared under four white-light stimulus conditions (dim pulse, dim step, bright pulse, and bright step). The Neuroptics, infrared, DP-2000 binocular pupillometer (30Hz sampling rate; 0.05mm resolution) was used in the monocular (right eye) stimulation mode. ResultsFor the majority of pupillary parameters and stimulus conditions, a Gaussian distribution best fit the data, with the apex centered in the low myopic range (−2.3 to −4.9D). Responsivity was reduced to either side of the apex. ConclusionsOver a range of dynamic and static pupillary parameters, the PLR was influenced by refractive error in both populations. In cases of high refractive error, the PLR parameters may need to be compensated for this factor for proper categorization and diagnosis.

Green Light-emitting Diodes Light Stimuli during Incubation Enhances Posthatch Growth without Disrupting Normal Eye Development of Broiler Embryos and Hatchlings.

Monochromatic green light-emitting diodes (LED) light stimuli influences the posthatch growth performance of chicks. This study was undertaken with the following objectives: i) to examine whether the green LED light stimuli induces an overheating effect by determining weight loss rate of fertile eggs during incubation period; ii) to look for the development of eyes and other primary organs at different ages of embryos and newly hatched chicks. Arbor Acres fertile broiler eggs (n = 480) were randomly assigned to 3 incubation groups and exposed to continuous white light, green light, or a dark environment (control) from the first day to 19 d of incubation. The light sourced from LED lamps with the intensity of 30 lx at eggshell level. The results showed that either green or white light stimuli during incubation did not significantly affect the weight loss rate of fertile eggs, hatching time, hatchability, chick embryo, or body weight (BW), the weight percentage of heart, liver, and eyes, as well as obvious systematic abnormalities in eye weight, side-to-side, back-to-front, or corneal diameter from 15 d of embryogenesis to 6 d of posthatch (p>0.05). Compared with the dark condition, green light stimuli during incubation tended to increase feed intake (p = 0.080), improved the BW gain of chicks during 0 to 6 day posthatch (p<0.05), and increased the percentage of pectoral muscle to the BW on 3- and 6-day-old chicks. In addition, embryos or chicks in green light had lower weight percentage of yolk retention on 19 d of embryogenesis and 1 d of posthatch in comparison to those in dark or white group (p<0.05). These results suggest that providing 30 lx green LED light stimuli during incubation has no detrimental effect on the development of eyes, heart and liver of embryos and hatchlings, but does have potential benefits in terms of enhancement of the chick growth during the early posthatch stages. In addition, the fertile broiler eggs stimulated with 30 lx green LED light during incubation does not cause an overheating effect.

Interaction of 12C ions with the mouse retinal response to light

Astronauts in orbit reported phosphenes varying in shape and orientation across the visual field; incidence was correlated with the radiation flux. Patients with skull tumors treated by 12C ions and volunteers whose posterior portion of the eye was exposed to highly ionizing particles in early studies reported comparable percepts. An origin in radiation activating the visual system is suggested. Bursts (∼4ms) of 12C ions evoked electrophysiological mass responses comparable to those to light in the retina of anesthetized wild-type mice at threshold flux intensities consistent with the incidence observed in humans. The retinal response amplitude increased in mice with ion intensity to a maximum at ∼2000 ions/burst, to decline at higher intensities; the inverted-U relationship suggests complex effects on retinal structures. Here, we show that bursts of 12C ions presented simultaneously to white light stimuli reduced the presynaptic mass response to light in the mouse retina, while increasing the postsynaptic retinal and cortical responses amplitude and the phase-locking to stimulus of cortical low frequency and gamma (∼25–45Hz) responses. These findings suggest 12C ions to interfere with, rather than mimicking the light action on photoreceptors; a parallel action on other retinal structures/mechanisms resulting in cortical activation is conceivable. Electrophysiological visual testing appears applicable to monitor the radiation effects and in designing countermeasures to prevent functional visual impairment during operations in space.

Spectral sensitivity of the compound eyes of Anomala corpulenta motschulsky (Coleoptera: Scarabaeoidea)

The scarab beetle, Anomala corpulenta Motschulsky (Coleoptera: Scarabaeoidea), is a widespread and destructive pest in China. Vision is one of the most important means of acquiring information about the external environment. In order to contribute to the understanding of the perception of visual stimuli in this species, the light sensitivity and spectral responses of the scarab beetle, A. corpulenta, were measured by using an electroretinogram (ERG) technique. In total, 14 monochromatic light intensities, between 340 and 605 nm, were applied to the compound eyes of A. corpulenta under varying levels of adaptation to dark and light conditions. The results showed that all light stimuli induced an ERG response, with varied amplitudes. The spectral sensitivity curve of dark-adapted eyes showed one major peak (~400 nm; near-ultraviolet), a secondary peak (from 498 to 562 nm; yellow-green) and the third peakat 460 nm. By contrast, in light-adapted eyes, only a near-UV peak was observed. From these results, we conclude that the compound eye of A. corpulenta is likely to have at least three spectral types of photoreceptor. Significance of differences were also recorded in the responses of male and female compound eyes, as well as diurnally and nocturnally. The amplitude of ERG in response to white-light stimuli varied with the light intensity: The stronger the luminance, the higher the ERG value. This suggests that the compound eye of A. corpulenta adapts quickly to changing light conditions, enabling A. corpulenta to maintain nocturnal activities.

Pupillary light reflex deficits in a canine model of late infantile neuronal ceroid lipofuscinosis

Late-infantile neuronal ceroid lipofuscinosis (CLN2) is a hereditary neurological disorder characterized by progressive retinal degeneration and vision loss, cognitive and motor decline, seizures, and pronounced brain atrophy. The progressive loss of neurological functions eventually leads to death, usually by the early teenage years. Utilizing a canine model of CLN2, therapeutic studies to inhibit the brain and retinal degenerations are currently under way. Using this dog model, studies were undertaken to compare quantitative assessments of the pupillary light reflex (PLR) and electroretinography (ERG) as tools for evaluating the effects of the disease on retinal function. The PLR and ERG were recorded in normal and CLN2-affected Dachshunds at 2 month intervals between the ages of 4 and 10 months. Using custom instrumentation for quantitative PLR assessments, a series of white light stimuli of varying intensity was used to elicit pupil constriction, and pupil images were recorded using continuous infrared illumination and an infrared-sensitive camera. Electroretinography was used to evaluate retinal function in the same dogs. As the disease progressed, affected dogs exhibited progressive and profound declines in ERG amplitudes under both scotopic and photopic conditions. With low intensity light stimuli, CLN2 was also accompanied by progressive deficits in the PLR. Changes in the PLR to dim light stimuli included significant deficits in latency, constriction velocity, constriction amplitude, and redilation velocity. However, despite the almost complete loss of detectable ERG responses by disease end stage, the PLR to bright stimuli was well preserved throughout the disease progression. These findings demonstrate that the PLR is much more sensitive than the ERG in detecting residual retinal function in animal models of retinal degenerative disease. The preservation of the PLR in dogs with profoundly depressed ERGs correlates with a preservation of visually-mediated behavior even late in the disease progression. Quantitative analysis of the PLR has potential as a biomarker in animal models of retinal degenerative diseases and in evaluating the efficacy of therapeutic interventions in preserving retinal function.

Quantitative Assessment of the Canine Pupillary Light Reflex

To develop instrumentation and methods for thorough quantitative assessment of the pupillary light reflex (PLR) in dogs under varying stimulus conditions. The PLR was recorded in normal Dachshunds using a custom system allowing full user control over stimulus intensity, color, and duration. Chemical restraint protocols were compared to determine which protocol provided for optimal baseline stability of pupil size and appropriate eye positioning. A series of white light stimuli of increasing intensity was used to elicit pupil constriction. Pupil images were concurrently recorded using continuous infrared illumination and an infrared-sensitive camera. The PLR was also recorded in response to blue and red stimuli. With injectable chemical restraint alone, spontaneous fluctuations in pupil size occurred independent of light stimulation, and spontaneous eye movements made it difficult to fully visualize the pupil. Combined injectable chemical and inhalation restraint provided a steady baseline pupil size throughout PLR assessment and allowed for stable positioning of the eye using a conjunctival stay suture. Robust PLRs were elicited with all light colors. PLR constriction amplitude increased with increasing flash intensity and ranged from 5% to 70%. A recording system and protocol have been developed to reliably quantify the canine PLR. The techniques and instrumentation will be useful for objective quantitative assessment of the PLR in dogs and other species in research applications and may be useful in clinical veterinary ophthalmology and neurology if PLR abnormalities detected with these procedures can be associated with specific diseases.

Chloride currents in cones modify feedback from horizontal cells to cones in goldfish retina

In neuronal systems, excitation and inhibition must be well balanced to ensure reliable information transfer. The cone/horizontal cell (HC) interaction in the retina is an example of this. Because natural scenes encompass an enormous intensity range both in temporal and spatial domains, the balance between excitation and inhibition in the outer retina needs to be adaptable. How this is achieved is unknown. Using electrophysiological techniques in the isolated retina of the goldfish, it was found that opening Ca(2+)-dependent Cl(-) channels in recorded cones reduced the size of feedback responses measured in both cones and HCs. Furthermore, we show that cones express Cl(-) channels that are gated by GABA released from HCs. Similar to activation of I(Cl(Ca)), opening of these GABA-gated Cl(-) channels reduced the size of light-induced feedback responses both in cones and HCs. Conversely, application of picrotoxin, a blocker of GABA(A) and GABA(C) receptors, had the opposite effect. In addition, reducing GABA release from HCs by blocking GABA transporters also led to an increase in the size of feedback. Because the independent manipulation of Ca(2+)-dependent Cl(-) currents in individual cones yielded results comparable to bath-applied GABA, it was concluded that activation of either Cl(-) current by itself is sufficient to reduce the size of HC feedback. However, additional effects of GABA on outer retinal processing cannot be excluded. These results can be accounted for by an ephaptic feedback model in which a cone Cl(-) current shunts the current flow in the synaptic cleft. The Ca(2+)-dependent Cl(-) current might be essential to set the initial balance between the feedforward and the feedback signals active in the cone HC synapse. It prevents that strong feedback from HCs to cones flood the cone with Ca(2)(+). Modulation of the feedback strength by GABA might play a role during light/dark adaptation, adjusting the amount of negative feedback to the signal to noise ratio of the cone output.

Glaukomerkennung mittels der Pupillenkampimetrie

The aim of the study was to find out if pupillographic assessment of the visual field by means of pupil campimetry can identify glaucomatous visual field defects and as such be used for glaucoma screening purposes. 20 patients with open angle glaucoma and 30 healthy persons were examined by means of pupil campimetry. All glaucoma patients had a glaucomatous visual field defect in at least one eye. The stimulus pattern consisted of 17 white-light stimuli which were presented within the 30° visual field, particularly in the Bjerrum region. The stimulus diameter was 6°. Each stimulus was presented for 200 ms and the interval between the stimuli was 1800 ms. Three stimulus intensities (16.4 cd/m2; 27.1 cd/m2 and 40.5 cd/m2) were tested. The individual pupil light reaction (PLR) amplitudes at all examined locations in the visual field, their sums and partial sums were compared between both groups by the two-sided two-sample t test. The diagnostic performance of the method in glaucoma diagnosis was evaluated by ROC curves (receiver operating characteristics). The average PLR at all locations in the visual field was reduced in glaucoma patients compared to healthy persons. The sums of the PLR were reduced in glaucoma patients as well. Significant differences in the PLR were found especially in the central and paracentral visual fields. The best AUC values (area under the curve) were reached with the highest stimulus intensity, the highest AUC value overall was 0.769. Although the difference in PLR between glaucoma patients and the control group was significant, the reached AUC values fell short of being ideal for screening purposes. A surprising finding was that the most central pupil response was reduced by the same amount as that in the Bjerrum region.