COLOUR PERCEPTION OF LED POINT LIGHT SOURCES IN SCOTOPIC VISION

When stimuli are made sufficiently small, colour-normal individuals report a loss in hue perception, similar to tritanopia. This effect is referred to as small-field tritanopia. The interaction between small-field tritanopia and the rods working in scotopic vision has not been clarified. In this study, the problem is investigated by freely adjusting the hue, lightness, and saturation of the test stimulus to match the colour of the reference stimulus by observers. Three colours on the blackbody radiation trajectory with colour temperatures of 3500K, 5400K, and 11600K were used as reference colours. Each stimulus subtended a diameter of 6' and 10.8'. The 5400K and 11600K stimuli were distributed diagonally from the lower left to the upper right of each reference stimulus in the CIE 1976 u’v’ uniform chromaticity scale diagram. The distribution was similar to those of tritanopia. For the 3500K stimulus, the result did not show the influence of small-field tritanopia.

The Impact of the Spectral Radiation Environment on the Maximum Absorption Wavelengths of Human Vision and Other Species

Since the earliest development of the eye (and vision) around 530 million years ago (Mya), it has evolved, adapting to different habitats, species, and changing environmental conditions on Earth. We argue that a radiation environment determined by the atmosphere played a determining role in the evolution of vision, specifically on the human eye, which has three vision regimes (photopic-, scotopic-, and mesopic vision) for different illumination conditions. An analysis of the irradiance spectra, reaching the shallow ocean depths, revealed that the available radiation could have determined the bandwidth of the precursor to vision systems, including human vision. We used the radiative transfer model to test the existing hypotheses on human vision. We argue that, once on the surface, the human photopic (daytime) and scotopic (night-time) vision followed different evolutionary directions, maximum total energy, and optimum information, respectively. Our analysis also suggests that solar radiation reflected from the moon had little or no influence on the evolution of scotopic vision. Our results indicate that, apart from human vision, the vision of only a few birds, rodents, and deep-sea fish are strongly correlated to the available radiation within their respective habitats.

Targeting ON-bipolar cells by AAV gene therapy stably reverses LRIT3-congenital stationary night blindness

AAV gene therapies aimed at curing inherited retinal diseases to date have typically focused on photoreceptors and retinal pigmented epithelia within the relatively accessible outer retina. However, therapeutic targeting in diseases such as congenital stationary night blindness (CSNB) that involve defects in ON-bipolar cells (ON-BCs) within the mid-retina has been challenged by the relative inaccessibility of the target cell in intact retinas, the limited transduction efficiency of these cells by existing AAV serotypes, poor availability of established ON-BC-specific promoters, and absence of appropriate patient-relevant large animal models. Here, we demonstrate safe and effective ON-BC targeting by AAV gene therapy in a recently characterized naturally-occurring canine model of CSNB, LRIT3-CSNB. To effectively target ON-BCs, new AAV capsid variants with ON-BC tropism and ON-BC specific modified GRM6 promoters were adopted to ensure cell-specific transgene expression. Notably, subretinal injection of one vector, AAVK9#4-shGRM6-cLRIT3-WPRE, significantly recovered rod-derived b-wave in all treated eyes (6/6) of adult dogs injected at 1-3 years of age. The robust therapeutic effect was evident 7 weeks post-injection and was sustained for at least 1 year in all treated eyes. Scotopic vision was significantly improved in treated eyes based on visually-guided obstacle course navigation. Restoration of LRIT3 signals was confirmed by immunohistochemistry. Thus, we report on the first ON-BC functional rescue in a large animal model using a novel AAV capsid variant and modified promoter construct optimized for ON-BC specificity, thereby establishing both proof-of-concept and a novel translational platform for treatment of CSNB in patients with defects in photoreceptor-to-bipolar signaling.

Adjustment of Lighting Parameters from Photopic to Mesopic Values in Outdoor Lighting Installations Strategy and Associated Evaluation of Variation in Energy Needs

The sensitivity of the human eye varies with the different lighting conditions to which it is exposed. The cone photoreceptors perceive the color and work for illuminance conditions greater than 3.00 cd/m² (photopic vision). Below 0.01 cd/m², the rods are the cells that assume this function (scotopic vision). Both types of photoreceptors work coordinately in the interval between these values (mesopic vision). Each mechanism generates a different spectral sensibility. In this work, the emission spectra of common sources in present public lighting installations are analyzed and their normative photopic values translated to the corresponding mesopic condition, which more faithfully represents the vision mechanism of our eyes in these conditions. Based on a common street urban configuration (ME6), we generated a large set of simulations to determine the ideal light point setup configuration (luminance and light point height vs. poles distance ratio) for each case of spectrum source. Finally, we analyze the derived energy variation from each design possibility. The results obtained may contribute to improving the criterion of light source selection and adapting the required regulatory values to the human eye vision process under normalized artificial street lighting condition, reaching an average energy saving of 15% and a reduction of 8% in terms of points of light required. They also offer a statistical range of energy requirements for lighting installation that can be used to generate accurate electrical designs or estimations without the necessity of defining the exact lighting configuration, which is 77.5% lower than conventional design criteria.

Function of cone and cone-related pathways in CaV1.4 IT mice

CaV1.4 L-type calcium channels are predominantly expressed in photoreceptor terminals playing a crucial role for synaptic transmission and, consequently, for vision. Human mutations in the encoding gene are associated with congenital stationary night blindness type-2. Besides rod-driven scotopic vision also cone-driven photopic responses are severely affected in patients. The present study therefore examined functional and morphological changes in cones and cone-related pathways in mice carrying the CaV1.4 gain-of function mutation I756T (CaV1.4-IT) using multielectrode array, patch-clamp and immunohistochemical analyses. CaV1.4-IT ganglion cell responses to photopic stimuli were seen only in a small fraction of cells indicative of a major impairment in the cone pathway. Though cone photoreceptors underwent morphological rearrangements, they retained their ability to release glutamate. Our functional data suggested a postsynaptic cone bipolar cell defect, supported by the fact that the majority of cone bipolar cells showed sprouting, while horizontal cells maintained contacts with cones and cone-to-horizontal cell input was preserved. Furthermore a reduction of basal Ca2+ influx by a calcium channel blocker was not sufficient to rescue synaptic transmission deficits caused by the CaV1.4-IT mutation. Long term treatments with low-dose Ca2+ channel blockers might however be beneficial reducing Ca2+ toxicity without major effects on ganglion cells responses.

Time-course of adaptations for electroretinography and pupillography

Cones are primarily involved in photopic vision and light adaptation. Rods are responsible for scotopic vision and dark adaptation. The typical time-courses of light and dark adaptations have been known for century. However, information regarding the minimal adaptation time for electroretinography (ERG) and pupillography would be helpful for practical applications and clinical efficiency. Therefore, we investigated the relationship between adaptation time and the parameters of ERG and pupillography. Forty-six eyes of 23 healthy women (mean age, 21.7 years) were enrolled. ERG and pupillography were tested for right and left eyes, respectively. ERG with a skin electrode was used to determine amplitude (µV) and implicit time (msec) by the records of rod-, flash-, cone-, and flicker-responses with white light (0.01–30 cd·s/m2). Infrared pupillography was used to record the pupillary response to 1-sec stimulation of red light (100 cd/m2). Cone- and flicker- (rod-, flash-, and pupil) responses were recorded after light (dark) adaptation at 1, 5, 10, 15, and 20 min. Amplitude was significantly different between 1 min and ≥5 or ≥10 min after adaptation in b-wave of cone- or rod-response, respectively. Implicit time differed significantly between 1 min and ≥5 min after adaptation with b-wave of cone- and rod-response. There were significant differences between 1 min and ≥10 or ≥5 min after dark adaptation in parameter of minimum pupil diameter or constriction rate, respectively. Consequently, light-adapted ERGs can be recorded, even in 5 min of light adaptation time without special light condition, whereas dark-adapted ERGs and pupillary response results can be obtained in 10 min or longer of dark adaptation time in complete darkness.

Vibrational Excitation Initiates Biomimetic Charge-Coupled Motions in the Electronic Ground State

<p>The concerted interplay between reactive nuclear and electronic motions in molecules actuates chemistry. Manipulating reaction pathways to achieve product selectivity via precise control of light-molecule interactions has allured chemists for decades. Yet it remains an elusive challenge in the electronic ground state, where conventional thermally-driven chemistry occurs. Here, we demonstrate that ground-state vibrational excitation of localised bridge modes initiates charge transfer in a donor-bridge-acceptor molecule in solution. The vibrationally-induced change in the ground-state electronic configuration is visualised by transient absorption spectroscopy, involving a mid-infrared pump and a visible probe, and detailed <i>ab initio </i>molecular dynamics simulations. Mapping the potential energy landscape unravels a hitherto undocumented charge-transfer-assisted double-bond isomerization channel in the electronic ground state. The reaction pathway bears remarkable parallels with the thermal isomerization process in rhodopsin, the retinal protein responsible for scotopic vision. Our results illustrate a generic protocol for activating key vibrational modes to drive photo-triggered ground-state reactions and motivate synthetic and catalytic strategies to achieving potentially new chemistry. </p>

Vibrational Excitation Initiates Biomimetic Charge-Coupled Motions in the Electronic Ground State

<p>The concerted interplay between reactive nuclear and electronic motions in molecules actuates chemistry. Manipulating reaction pathways to achieve product selectivity via precise control of light-molecule interactions has allured chemists for decades. Yet it remains an elusive challenge in the electronic ground state, where conventional thermally-driven chemistry occurs. Here, we demonstrate that ground-state vibrational excitation of localised bridge modes initiates charge transfer in a donor-bridge-acceptor molecule in solution. The vibrationally-induced change in the ground-state electronic configuration is visualised by transient absorption spectroscopy, involving a mid-infrared pump and a visible probe, and detailed <i>ab initio </i>molecular dynamics simulations. Mapping the potential energy landscape unravels a hitherto undocumented charge-transfer-assisted double-bond isomerization channel in the electronic ground state. The reaction pathway bears remarkable parallels with the thermal isomerization process in rhodopsin, the retinal protein responsible for scotopic vision. Our results illustrate a generic protocol for activating key vibrational modes to drive photo-triggered ground-state reactions and motivate synthetic and catalytic strategies to achieving potentially new chemistry. </p>

Scotopic Vision Is Selectively Processed in Thick-Type Columns in Human Extrastriate Cortex

In humans, visual stimuli can be perceived across an enormous range of light levels. Evidence suggests that different neural mechanisms process different subdivisions of this range. For instance, in the retina, stimuli presented at very low (scotopic) light levels activate rod photoreceptors, whereas cone photoreceptors are activated relatively more at higher (photopic) light levels. Similarly, different retinal ganglion cells are activated by scotopic versus photopic stimuli. However, in the brain, it remains unknown whether scotopic versus photopic information is: 1) processed in distinct channels, or 2) neurally merged. Using high-resolution functional magnetic resonance imaging at 7 T, we confirmed the first hypothesis. We first localized thick versus thin-type columns within areas V2, V3, and V4, based on photopic selectivity to motion versus color, respectively. Next, we found that scotopic stimuli selectively activated thick- (compared to thin-) type columns in V2 and V3 (in measurements of both overlap and amplitude) and V4 (based on overlap). Finally, we found stronger resting-state functional connections between scotopically dominated area MT with thick- (compared to thin-) type columns in areas V2, V3, and V4. We conclude that scotopic stimuli are processed in partially segregated parallel streams, emphasizing magnocellular influence, from retina through middle stages of visual cortex.