Photoreceptors and diurnal variation in spectral sensitivity in the fiddler crab Gelasimus dampieri

Colour signals, and the ability to detect them, are important for many animals and can be vital to their survival and fitness. Fiddler crabs use colour information to detect and recognise conspecifics, but their colour vision capabilities remain unclear. Many studies have attempted to measure their spectral sensitivity and identify contributing retinular cells, but the existing evidence is inconclusive. We used electroretinogram (ERG) measurements and intracellular recordings from retinular cells to estimate the spectral sensitivity of Gelasimus dampieri and to track diurnal changes in spectral sensitivity. G. dampieri has a broad spectral sensitivity and is most sensitive to wavelengths between 420 and 460 nm. Selective adaptation experiments uncovered an ultraviolet (UV) retinular cell with a peak sensitivity shorter than 360 nm. The species' spectral sensitivity above 400 nm is too broad to be fitted by a single visual pigment and using optical modelling, we provide evidence that at least two medium-wavelength sensitive (MWS) visual pigments are contained within a second blue-green sensitive retinular cell. We also found a ∼25 nm diurnal shift in spectral sensitivity towards longer wavelengths in the evening in both ERG and intracellular recordings. Whether the shift is caused by screening pigment migration or changes in opsin expression remains unclear, but the observation shows the diel dynamism of colour vision in this species. Together, these findings support the notion that G. dampieri possesses the minimum requirement for colour vision, with UV and blue/green receptors, and help to explain some of the inconsistent results of previous research.

Usefulness of handheld electroretinogram system for diagnosing blue-cone monochromatism in children

PURPOSE

To report the diagnosis of three childhood patients with blue-cone monochromatism (BCM) using S-cone electroretinograms (ERG) recorded with RETeval^® Complete.

STUDY DESIGN

Prospective clinical study.

METHODS

We examined three boys initially suspected of having rod monochromatism. S-cone ERG was performed with red background and blue flashed light stimulation using two different intensities: 0.25 cd × s/m² and 1 cd × s/m².

RESULTS

Case 1 was a 12-year-old boy with a visual acuity of 0.1 OU. Case 2 was an 8-year-old boy with a visual acuity of 0.3 OD and 0.2 OS. Both cases showed a myopic fundus and nystagmus without any other ocular abnormalities. Case 3 was a 6-year-old boy with a visual acuity of 0.3 OD and 0.4 OS. He also showed myopic fundus changes, but nystagmus was not observed. Rod and maximal responses recorded with RETeval^® were likely to be within normal range; however, cone responses were absent in all cases. S-cone ERGs showed positive responses at 40 ms with 0.25 cd × s/m² intensity in Case 2, and at approximately 30-40 ms with 1.0 cd × s/m² intensity in all three cases. These ERG findings led to a diagnosis of BCM.

CONCLUSIONS

S-cone ERG of RETeval^® was helpful in diagnosing with minimal invasion BCM in childhood patients.

A Visual Distortion Sensing Model for Early Detection of Macular Disorders

This paper presents a novel method to model the deformations that occur in the retina due to macular disorders such as Age-related Macular Degeneration (AMD). In this model, the retinal pigment epithelium (RPE) covered with cones and rods is considered as a uniform layer of known pixels. The projected image on these pixels is perceived as per this model. Furthermore, this model can efficiently be used to generate the test patterns for an accurate and efficient method for monitoring macular disorder. In this proposed model, two major geometric shapes of retinal deformation are taken into account. Both colourful and grayscale images are employed to estimate the perceived images under various circumstances and inputs. Based on these results, the proposed model can be used for the assessment of the progression of macular disorders.Clinical relevance-Retinal Pigment Epithelium (RPE), Field of view (FOV), Visual Distortion (VD).

A kinetic analysis of mouse rod and cone photoreceptor responses

KEY POINTS

Most vertebrate eyes have rods for dim-light vision and cones for brighter light and higher temporal sensitivity. Rods evolved from cone-like precursors through expression of different transduction genes or the same genes at different expression levels, but we do not know which molecular differences were most important. We approached this problem by analysing rod and cone responses with the same model but with different values for model parameters. We showed that, in addition to outer-segment volume, the most important differences between rods and cones are: (1) decreased transduction gain, reflecting smaller amplification in the G-protein cascade; (2) a faster rate of turnover of the second messenger cGMP in darkness; and (3) an accelerated rate of decay of the effector enzyme phosphodiesterase and perhaps also of activated visual pigment. We believe our analysis has identified the principal alterations during evolution responsible for the duplex retina.

ABSTRACT

Most vertebrates have rod and cone photoreceptors, which differ in their sensitivity and response kinetics. We know that rods evolved from cone-like precursors through the expression of different transduction genes or the same genes at different levels, but we do not know which molecular differences were most important. We have approached this problem in mouse retina by analysing the kinetic differences between rod flash responses and recent voltage-clamp recordings of cone flash responses, using a model incorporating the principal features of photoreceptor transduction. We apply a novel method of analysis using the log-transform of the current, and we ask which of the model's dynamic parameters need be changed to transform the flash response of a rod into that of a cone. The most important changes are a decrease in the gain of the response, reflecting a reduction in amplification of the transduction cascade; an increase in the rate of turnover of cGMP in darkness; and an increase in the rate of decay of activated phosphodiesterase, with perhaps also an increase in the rate of decay of light-activated visual pigment. Although we cannot exclude other differences, and in particular alterations in the Ca2+ economy of the photoreceptors, we believe that we have identified the kinetic parameters principally responsible for the differences in the flash responses of the two kinds of photoreceptors, which were likely during evolution to have resulted in the duplex retina.

Validating Fluorescent Chrnb4.EGFP Mouse Models for the Study of Cone Photoreceptor Degeneration

Purpose

To validate the application of a known transgenic mouse line with green fluorescent cones (Chrnb4.EGFP) to study cone photoreceptor biology and function in health and disease.

Methods

Chrnb4.EGFP retinas containing GFP+ cones were compared with retinas without the GFP transgene via immunohistochemistry, quantitative real-time polymerase chain reaction, electroretinograms, and flow cytometry. The Chrnb4.EGFP line was backcrossed to the mouse models of cone degeneration, Pde6ccpfl1 and Gnat2cpfl3 , generating the new lines Gnat2.GFP and Pde6c.GFP, which were also studied as described.

Results

GFP expression spanned the length of the cone cell in the Chrnb4.EGFP line, as well as in the novel Gnat2.GFP and Pde6c.GFP lines. The effect of GFP expression showed no significant changes to outer nuclear layer cell death, cone-specific gene expression, and immune response activation. A temporal decrease in GFP expression over time was observed, but GFP fluorescence was still detected through flow cytometry as late as 6 months. Furthermore, a functional analysis of photopic and scotopic electroretinogram responses of the Chrnb4 mouse showed no significant difference between GFP- and GFP+ mice, whereas electroretinogram recordings for the Pde6c.GFP and Gnat2.GFP lines matched previous reports from the original lines.

Conclusions

This study demonstrates that the Chrnb4.EGFP mouse can be a powerful tool to overcome the limitations of studying cone biology, including the use of this line to study different types of cone degeneration.

Translational Relevance

This work validates research tools that could potentially offer more reliable preclinical data in the development of treatments for cone-mediated vision loss conditions, shortening the gap to clinical translation.

Electroretinogram analysis of zebrafish retinal function across development

PURPOSE

The electroretinogram (ERG) is a powerful approach for investigating visual function in zebrafish ocular disease models. However, complexity, cost, and a literature gap present as significant barriers for the introduction of this technology to new zebrafish laboratories. Here, we introduce a simplified and effective method to obtain zebrafish ERGs.

METHODS

In-house assembled recording electrodes and a custom 3D-printed platform were used to gather high-quality and consistent ERG data from zebrafish at 3 developmental timepoints-larval, juvenile, and adult. Fish were tested under both scotopic (dark-adapted) and photopic (light-adapted) conditions to differentiate between the rod and cone systems, respectively.

RESULTS

Robust ERG waveforms across all developmental timepoints were obtained using the methodology presented here. We observed an overall increase in signal amplitude as development progressed, reflecting maturation of the zebrafish retina. Oscillatory potentials could also be isolated from the generated waveforms.

CONCLUSIONS

This simplified approach to the zebrafish ERG can generate waveforms comparable to the existing approaches and helps reduce barriers for zebrafish laboratories studying ocular development and disease.

Spectral sensitivity of cone vision in the diurnal murid Rhabdomys pumilio

An animal's temporal niche - the time of day at which it is active - is known to drive a variety of adaptations in the visual system. These include variations in the topography, spectral sensitivity and density of retinal photoreceptors, and changes in the eye's gross anatomy and spectral transmission characteristics. We have characterised visual spectral sensitivity in the murid rodent Rhabdomys pumilio (the four-striped grass mouse), which is in the same family as (nocturnal) mice and rats but exhibits a strong diurnal niche. As is common in diurnal species, the R. pumilio lens acts as a long-pass spectral filter, providing limited transmission of light <400 nm. Conversely, we found strong sequence homologies with the R. pumilio SWS and MWS opsins and those of related nocturnal species (mice and rats) whose SWS opsins are maximally sensitive in the near-UV. We continued to assess in vivo spectral sensitivity of cone vision using electroretinography and multi-channel recordings from the visual thalamus. These revealed that responses across the human visible range could be adequately described by those of a single pigment (assumed to be MWS opsin) maximally sensitive at ∼500 nm, but that sensitivity in the near-UV required inclusion of a second pigment whose peak sensitivity lay well into the UV range (λmax<400 nm, probably ∼360 nm). We therefore conclude that, despite the UV-filtering effects of the lens, R. pumilio retains an SWS pigment with a UV-A λmax In effect, this somewhat paradoxical combination of long-pass lens and UV-A λmax results in narrow-band sensitivity for SWS cone pathways in the UV-A range.

'The last channel': vision at the temporal margin of the field

The human visual field, on the temporal side, extends to at least 90° from the line of sight. Using a two-alternative forced-choice procedure in which observers are asked to report the direction of motion of a Gabor patch, and taking precautions to exclude unconscious eye movements in the direction of the stimulus, we show that the limiting eccentricity of image-forming vision can be established with precision. There are large, but reliable, individual differences in the limiting eccentricity. The limiting eccentricity exhibits a dependence on log contrast; but it is not reduced when the modulation visible to the rods is attenuated, a result compatible with the histological evidence that the outermost part of the retina exhibits a high density of cones. Our working hypothesis is that only one type of neural channel is present in the far periphery of the retina, a channel that responds to temporally modulated stimuli of low spatial frequency and that is directionally selective.

Early Cone Photoreceptor Outer Segment Length Shortening in RPGR X-Linked Retinitis Pigmentosa

INTRODUCTION

Introduction of retinal gene therapy requires established outcome measures along with thorough understanding of the pathophysiology. Evidence of early, thinned outer segments in RPGR X-linked retinitis pigmentosa could help understand how the level of cone photoreceptor involvement translates to visual potential.

OBJECTIVE

Analysis of foveal photoreceptor outer segment length in a young cohort of RPGR patients to help clarify the reason for absent maximal visual acuity seen.

METHODS

Case-control study of RPGR patients. Quantitative measurement of photoreceptor outer segment by OCT.

RESULTS

Eighteen male RPGR patients and 30 normal subjects were included. Outer segment thickness differed significantly between the RPGR and normal eyes (p < 0.0005). Mean outer segment values were 35.6 ± 2.3 µm and 35.4 ± 2.6 µm for RPGR right and left eyes, respectively. In normal eyes, the mean outer segment thickness was 61.4 ± 0.7 µm for right eyes and 62.4 ± 0.7 µm for left eyes.

CONCLUSIONS

Patients with RPGR X-linked retinitis pigmentosa show thinning of the foveal photoreceptor outer segment thickness early in the disease course, which could be an explanation for the lower maximum visual acuity seen. These findings must be taken into consideration when assessing efficacy outcome measures in retinal gene therapy trials.

[Retinitis pigmentosa]

Retinitis pigmentosa is the most frequent hereditary dystrophy of the retina, with a global prevalence of 1/4.000. The underlying mechanism involves progressive loss, first of the rod photoreceptor cells, followed by the cone photoreceptor cells. Finally, complete blindness may occur. Genetic transmission is known but most cases are sporadic. Few effective treatments exist nowadays and hence regular follow-up is required in a revalidation center.

Blinded by the light: a nonhuman primate model of achromatopsia

Achromatopsia is an inherited retinal degeneration characterized by the loss of cone photoreceptor function. In this issue of the JCI, Moshiri et al. characterize a naturally occurring model of the disease in the rhesus macaque caused by homozygous mutations in the phototransduction enzyme PDE6C. Using retinal imaging, and electrophysiologic and biochemical methods, the authors report a clinical phenotype nearly identical to the human condition. These findings represent the first genetic nonhuman primate model of an inherited retinal disease, and provide an ideal testing ground for the development of novel gene replacement, gene editing, and cell replacement therapies for cone dystrophies.

High-Resolution Retinal Imaging Reveals Preserved Cone Photoreceptor Density and Choroidal Thickness in Female Carriers of Choroideremia

BACKGROUND AND OBJECTIVE

To characterize the photoreceptors and choroidal morphology of heterozygous female carriers of choroideremia who typically do not have any visual defects but can have severe funduscopic changes.

PATIENTS AND METHODS

This was a clinical case series study. Detailed ophthalmic examinations were performed on six female carriers from four families with choroideremia. The subfoveal choroidal thickness (SFCT) was determined by spectral-domain optical coherence tomography (SD-OCT) and the cone photoreceptor density by adaptive optics (AO) retinal imaging. SFCT and cone densities of the carriers were compared to that of normal eyes of healthy subjects.

RESULTS

The mean age of the carriers was 42.5 years. Fundus photographs showed diffuse, patchy depigmentation; however, the SFCT was within the normal limits. AO retinal imaging revealed preserved cone densities at temporal eccentricities from 2 to 8 angular degrees.

CONCLUSIONS

The findings indicate that despite the presence of distinctive depigmentation of the retinal pigment epithelium in female carriers of choroideremia, their cone photoreceptor densities and SFCT are well-preserved. These observations may account for the good visual acuity and lack of an awareness of visual disturbances. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:76-85.].

Multimodal Imaging in Choroideremia

Choroideremia (CHM) is associated with progressive degeneration of the retinal pigment epithelium (RPE), choriocapillaris (CC), and photoreceptors. As animal models of CHM are lacking, most information about cell survival has come from imaging affected patients. This chapter discusses a combination of imaging techniques, including fundus-guided microperimetry, confocal and non-confocal adaptive optics scanning laser ophthalmoscopy (AOSLO), fundus autofluorescence (FAF), and swept-source optical coherence tomography angiography (SS-OCTA) to analyze macular sensitivity, cone photoreceptor outer and inner segment structure, RPE structure, and CC perfusion, respectively. Combined imaging modalities such as those described here can provide sensitive measures of monitoring retinal structure and function in patients with CHM.

A CEP290 C-Terminal Domain Complements the Mutant CEP290 of Rd16 Mice In Trans and Rescues Retinal Degeneration

Mutations in CEP290 cause ciliogenesis defects, leading to diverse clinical phenotypes, including Leber congenital amaurosis (LCA). Gene therapy for CEP290-associated diseases is hindered by the 7.4 kb CEP290 coding sequence, which is difficult to deliver in vivo. The multi-domain structure of the CEP290 protein suggests that a specific CEP290 domain may complement disease phenotypes. Thus, we constructed AAV vectors with overlapping CEP290 regions and evaluated their impact on photoreceptor degeneration in Cep290rd16/rd16 and Cep290rd16/rd16;Nrl-/- mice, two models of CEP290-LCA. One CEP290 fragment (the C-terminal 989 residues, including the domain deleted in mutant mice) reconstituted CEP290 function and resulted in cone preservation and delayed rod death. The CEP290 C-terminal domain also improved cilia phenotypes in mouse embryonic fibroblasts and iPSC-derived retinal organoids carrying the Cep290rd16 mutation. Our study strongly argues for in trans complementation of CEP290 mutations by a cognate fragment and suggests therapeutic avenues.

Cone and melanopsin contributions to human brightness estimation: comment

A recent study of large-field subjective brightness perception under different narrowband spectra and different luminances revealed distinct contributions of cone photoreceptors and intrinsically photosensitive retinal ganglion cells containing the photopigment melanopsin. The data from this study were analyzed with a recently published model of spectral sensitivity for full-field brightness incorporating three primary channels: a luminance (achromatic) channel, a blue-yellow opponent color channel, and a melanopsin channel. There was good agreement between predictions based on this model and the recently published brightness perception data.

Isolation of photoreceptors from mature, developing, and regenerated zebrafish retinas, and of microglia/macrophages from regenerating zebrafish retinas

This paper describes experimental procedures for the dissociation of retinal cells of the zebrafish (Danio rerio) for subsequent fluorescence-activated cell sorting (FACS) and gene expression studies. Methods for dissociation of zebrafish retinas followed by FACS and RNA isolation were optimized. This methodology was applied to isolate pure sorted samples of rods, long wavelength-sensitive (LWS) cones, medium wavelength-sensitive (MWS; RH2-2) cones, short wavelength-sensitive (SWS2) cones, and UV-sensitive (SWS1) cones from retinas obtained at selective life-history stages of the zebrafish, and for some of these photoreceptors, following retinal regeneration. We also successfully separated lws1-expressing and lws2-expressing LWS cones from fish of a transgenic line in which lws1 is reported with green fluorescence protein (GFP) and lws2 is reported with red fluorescence protein (RFP). Microglia/macrophages were successfully sorted from regenerating retinas (7 days after a cytotoxic lesion) of a transgenic line in which these immune cells express GFP. Electropherograms verified downstream isolation of high-quality RNA from sorted samples. Examples of post-sorting analysis, as well as results of qRT-PCR studies, validated the purity of sorted populations. For example, qRT-PCR samples derived from isolated Rh2-2 cones contained detectable rh2-2 (opn1mw2) opsin transcripts, but lws opsin transcripts (lws1/opn1lw1, lws2/opn1lw2) were not detected, suggesting that the procedure likely separated double cone pairs. Through this method, pure, sorted cell samples can provide RNA that is reliable for downstream gene expression analyses, such as qRT-PCR and RNA-seq, which may reveal molecular signatures of photoreceptors and microglia for comparative transcriptomics studies.

Genotype determination of the OPN1LW/OPN1MW genes: novel disease-causing mechanisms in Japanese patients with blue cone monochromacy

Blue cone monochromacy (BCM) is characterized by loss of function of both OPN1LW (the first) and OPN1MW (the downstream) genes on the X chromosome. The purpose of this study was to investigate the first and downstream genes in the OPN1LW/OPN1MW array in four unrelated Japanese males with BCM. In Case 1, only one gene was present. Abnormalities were found in the promoter, which had a mixed unique profile of first and downstream gene promoters and a -71A > C substitution. As the promoter was active in the reporter assay, the cause of BCM remains unclear. In Case 2, the same novel mutation, M273K, was present in exon 5 of both genes in a two-gene array. The mutant pigments showed no absorbance at any of the wavelengths tested, suggesting that the mutation causes pigment dysfunction. Case 3 had a large deletion including the locus control region and entire first gene. Case 4 also had a large deletion involving exons 2-6 of the first gene. As an intact LCR was present upstream and one apparently normal downstream gene was present, BCM in Case 4 was not ascribed solely to the deletion. The deletions in Cases 3 and 4 were considered to have been caused by non-homologous recombination.

Chaos and multi-scroll attractors in RCL-shunted junction coupled Jerk circuit connected by memristor

In this paper, a new four-variable dynamical system is proposed to set chaotic circuit composed of memristor and Josephson junction, and the dependence of chaotic behaviors on nonlinearity is investigated. A magnetic flux-controlled memristor is used to couple with the RCL-shunted junction circuit, and the dynamical behaviors can be modulated by changing the coupling intensity between the memristor and the RCL-shunted junction. Bifurcation diagram and Lyapunov exponent are calculated to confirm the emergence of chaos in the improved dynamical system. The outputs and dynamical behaviors can be controlled by the initial setting and external stimulus as well. As a result, chaos can be suppressed and spiking occurs in the sampled outputs under negative feedback, while applying positive feedback type via memristor can be effective to trigger chaos. Furthermore, it is found that the number of multi-attractors in the Jerk circuit can be modulated when memristor coupling is applied on the circuit. These results indicate that memristor coupling can be effective to control chaotic circuits and it is also useful to reproduce dynamical behaviors for neuronal activities.

Distribution of cone density, spacing and arrangement in adult healthy retinas with adaptive optics flood illumination

The aim of this article is to analyse cone density, spacing and arrangement using an adaptive optics flood illumination retina camera (rtx1^™) on a healthy population. Cone density, cone spacing and packing arrangements were measured on the right retinas of 109 subjects at 2°, 3°, 4°, 5° and 6° of eccentricity along 4 meridians. The effects of eccentricity, meridian, axial length, spherical equivalent, gender and age were evaluated. Cone density decreased on average from 28 884 ± 3 692 cones/mm², at 2° of eccentricity, to 15 843 ± 1 598 cones/mm² at 6°. A strong inter-individual variation, especially at 2°, was observed. No important difference of cone density was observed between the nasal and temporal meridians or between the superior and inferior meridians. However, the horizontal and vertical meridians differed by around 14% (T-test, p<0.0001). Cone density, expressed in units of area, decreased as a function of axial length (r² = 0.60), but remained constant (r² = 0.05) when cone density is expressed in terms of visual angle supporting the hypothesis that the retina is stretched during the elongation of the eyeball. Gender did not modify the cone distribution. Cone density was slightly modified by age but only at 2°. The older group showed a smaller density (7%). Cone spacing increased from 6,49 ± 0,42 μm to 8,72 ± 0,45 μm respectively between 2° and 6° of eccentricity. The mosaic of the retina is mainly triangularly arranged (i.e. cells with 5 to 7 neighbors) from 2° to 6°. Around half of the cells had 6 neighbors.

[Research progress of treatment strategies for retinitis pigmentosa]

Retinitis pigmentosa (RP) is a genetically heterogeneous group of hereditary retinal disorders characterized by photoreceptor cell death, associated with night blindness, vision loss, progressive peripheral visual field loss and abnormalities in the electroretinogram. A number of gene defects have so far been associated with RP, which cause a progressive loss of rod photoreceptor function, followed by cone photoreceptor dysfunction and eventually complete blindness. The rate of blindness related to RP is high. At present there is no effective therapeutic strategy for RP. In recent years, with the progress of molecular biology technique, many new therapeutic approaches have become promising. This article summarizes the pathogenesis of RP and gives a brief overview of related research progress of RP therapeutic strategies. (Chin J Ophthalmol, 2017, 53: 148-153).

Novel mutations in the gene for α-subunit of retinal cone cyclic nucleotide-gated channels in a Japanese patient with congenital achromatopsia

PURPOSE

To present the characteristics and pathology of a patient with congenital achromatopsia.

PATIENT AND METHODS

The patient was a 22-year-old Japanese woman who was 8 years old when she first visited our clinic. Comprehensive ophthalmic examinations including visual acuity measurements, perimetry, optical coherence tomography (OCT), fundus autofluorescence (FAF) imaging, electroretinography (ERG), and color vision tests were performed. Her genomic DNA was used as the template for the amplification of exons of five candidate genes for achromatopsia; CNGA3, CNGB3, GNAT2, PDE6C, and PDE6H, and the amplified products were sequenced. A missense mutation, found in the CNGA3, was studied both electrophysiologically and biochemically.

RESULTS

Her phenotype was typical of congenital complete achromatopsia. She was followed for 14 years, and her vision and fundus findings were stable. However, the scotopic ERG b-waves at age 22 were smaller than those at age 8, and her FAF images showed increased autofluorescence in both maculae. Genetic examinations revealed combined heterozygous mutations of c.997_998delGA and p.M424V in the CNGA3 gene. The homomeric channel consisting of the CNGA3 subunit with the p.M424V mutation had a weak cGMP-activated current in patch-clamp recordings. In heterologous expression analyses, the expression at the cell surface of the mutant CNGA3 subunit was about 28 % of the wild type.

CONCLUSIONS

The two novel mutations found in the CNGA3 gene, c.997_998delGA and p.M424V, can cause complete achromatopsia. The vision of the patient was stationary until the third decade of life although the FAF was altered at the age of 22 years.

[Analysis of Observers Metamerism Differences for Different Retinal Cone Visual Responses]

In order to investigate the cone's spectral responses under different conditions for different aged observers with normal color vision, nine color patches with different hue angles distributed uniformly on the CIELAB color space were prepared, and the 27-35 observers were organized to carry out color matching experiments on a monitor to match the nine printed color samples under four different viewing conditions including two illuminances, and two viewing fields. The spectral data obtained from the color matching experiments were compared with the spectral data of the nine target colors and used to test the performances of eleven color matching functions including CIE1931, CIE1964, CIE2006, Sarkar's S1-S8 in terms of the percentage of the minimum CIEDE2000 value. For the four experiments, CIE2006 and S6 performed the best and with S1, S2 the worst. For different observers, the visual spectral responses' of the retinal cone are different and the age has the obvious influence on the visual spectral responses. The observer metamerism is mainly caused by the different spectral response of the (A) channel and for most observers the differences appeared at the responses of the peak wavelength, and the shift of the peak wavelength has no significant influence on the observers metamerism. The experimental results can provide evidences for the classification of the color matching functions for different observer categories and theoretical basis for the investigation of the observers metamerism.

Viral-mediated RdCVF and RdCVFL expression protects cone and rod photoreceptors in retinal degeneration

Alternative splicing of nucleoredoxin-like 1 (Nxnl1) results in 2 isoforms of the rod-derived cone viability factor. The truncated form (RdCVF) is a thioredoxin-like protein secreted by rods that promotes cone survival, while the full-length isoform (RdCVFL), which contains a thioredoxin fold, is involved in oxidative signaling and protection against hyperoxia. Here, we evaluated the effects of these different isoforms in 2 murine models of rod-cone dystrophy. We used adeno-associated virus (AAV) to express these isoforms in mice and found that both systemic and intravitreal injection of engineered AAV vectors resulted in RdCVF and RdCVFL expression in the eye. Systemic delivery of AAV92YF vectors in neonates resulted in earlier onset of RdCVF and RdCVFL expression compared with that observed with intraocular injection using the same vectors at P14. We also evaluated the efficacy of intravitreal injection using a recently developed photoreceptor-transducing AAV variant (7m8) at P14. Systemic administration of AAV92YF-RdCVF improved cone function and delayed cone loss, while AAV92YF-RdCVFL increased rhodopsin mRNA and reduced oxidative stress by-products. Intravitreal 7m8-RdCVF slowed the rate of cone cell death and increased the amplitude of the photopic electroretinogram. Together, these results indicate different functions for Nxnl1 isoforms in the retina and suggest that RdCVF gene therapy has potential for treating retinal degenerative disease.