Blue Cone Research Articles

Samd7 represses short-wavelength cone genes to preserve long-wavelength cone and rod photoreceptor identity

The role of transcription factors in photoreceptor gene regulation is fairly well understood, but knowledge of the cell-type-specific function of transcriptional cofactors remains incomplete. Here, we show that the transcriptional corepressor samd7 promotes rod differentiation and represses short-wavelength cone genes in long-wavelength cones in zebrafish. In samd7-/- retinas, red cones are transformed into hybrid red/ultraviolet (UV) cones, green cones are absent, the number of blue cones is approximately doubled, and the number of rods is greatly reduced. We also find that mouse Samd7 represses S-opsin expression in dorsal M-cones-analogous to its role in repressing UV cone genes in zebrafish red cones. Thus, samd7 plays a key role in ensuring appropriate patterns of gene expression in rods and cone subtypes of both zebrafish and mice.

Deciphering the Physical Characteristics of Ophthalmic Filters Used in Optometric Vision Therapy.

This paper aimed to measure and characterize eleven monochromatic filters and twenty-two combinations used empirically to treat patients with visual dysfunctions to propose enhanced protocols based on solid evidence. Their wavelength, transmittance, and relative sensitivity were defined on the retinal cone cells. A double-beam UV-VIS-NIR spectrophotometer, VARIAN brand, Cary 5000 model, owned by the National Center of Metrology, with high precision and accuracy, was used to characterize all filters. Filters were purchased from Optomatters Corporation, Belgium. When two or three filters are combined, their transmittance and relative sensitivity on the retinal cone cells decrease regardless of wavelength. As a result, the efficiency of combined filters may decrease during treatments. Additionally, most filters and combinations, regardless of the wavelength, transmit a considerable percentage of light from the red spectrum. A depressant is the best monochromatic filter, and Upsilon-Neurasthenic is the strongest combination to stimulate blue cone cells. In contrast, Stimulant and Delta-Theta are best for red and green cone cells. Mu-Delta and Mu-Theta can be interchangeable, as well as Alpha-Delta and Alpha-Theta. Results suggest that the current phototherapy treatment protocol must be deeply revised, and the number of filters and combinations should be reduced to reduce costs and time and boost efficiency.

Ultrafast transient absorption spectra and kinetics of human blue cone visual pigment at room temperature

The ultrafast photochemical reaction mechanism, transient spectra, and transition kinetics of the human blue cone visual pigment have been recorded at room temperature. Ultrafast time-resolved absorption spectroscopy revealed the progressive formation and decay of several metastable photo-intermediates, corresponding to the Batho to Meta-II photo-intermediates previously observed with bovine rhodopsin and human green cone opsin, on the picosecond to millisecond timescales following pulsed excitation. The experimental data reveal several interesting similarities and differences between the photobleaching sequences of bovine rhodopsin, human green cone opsin, and human blue cone opsin. While Meta-II formation kinetics are comparable between bovine rhodopsin and blue cone opsin, the transition kinetics of earlier photo-intermediates and qualitative characteristics of the Meta-I to Meta-II transition are more similar for blue cone opsin and green cone opsin. Additionally, the blue cone photo-intermediate spectra exhibit a high degree of overlap with uniquely small spectral shifts. The observed variation in Meta-II formation kinetics between rod and cone visual pigments is explained based on key structural differences.

Ocular genetics in the Japanese population.

In today's globalized society, ophthalmologists can examine people of different ethnicities regardless of where they live. The frequency of disease-causing genes varies according to a patient's ethnic background. We explain genetic findings for Japanese patients with inherited eye diseases. Ocular genetics has made great advances over the past 30 years. For example, detecting mutations at nucleotide position 11778 in mitochondrial DNA was useful in the genetic diagnosis of Leber's hereditary optic neuropathy (LHON). I evaluated the genotype-phenotype relationship in cases of corneal dystrophy and inherited retinal dystrophy (IRD). I identified the entire exon sequence of the eyes shut homolog (EYS) gene in patients with autosomal recessive retinitis pigmentosa (RP). EYS gene mutations are the most frequent cause of autosomal recessive RP. RPGRIP1 may be a common causative gene with early-onset severe retinal dystrophy, including Leber congenital amaurosis. However, some genes have complex structures that are difficult to analyze, including the OPN1LW/OPN1MW gene cluster in blue cone monochromacy and the IKBKG/NEMO genes in incontinentia pigmenti. This review will also present two cases with uniparental disomy, a case of IRD with double mutations, and a case with RP complicated with LHON-like neuropathy. Precise understanding of the effects of genetic variants may reveal differences in the clinical characteristics of patients with the same variant. When starting genome medicine, accurately diagnosing the patient, making accurate prediction, determining the genetic pattern, and providing genetic counseling are important. Above all, that both the doctors and patients understand genetic diseases correctly is important.

Phylogenomic analysis reveals the evolutionary history of Paleartic needle-leaved junipers

Needle-leaved junipers (Juniperus sect. Juniperus, Cupressaceae) are coniferous trees and shrubs with red or blue fleshy cones. They are distributed across Asia, Macaronesia and the Mediterranean Basin, with one species (J. communis) having a circumboreal distribution. Here we aim to resolve the phylogeny of this clade to infer its intricate evolutionary history. To do so, we built a comprehensive, time-calibrated phylogeny using genotyping-by-sequencing (GBS) and combine it with species occurrence using phylogeographic tools. Our results provide solid phylogenetic resolution to propose a new taxonomic classification and a biogeographical history of the section. Specifically, we confirm the monophyly of two groups within J. sect. Juniperus: the Asian (blue-cone) species including the circumboreal J. communis, and the Mediterranean-Macaronesian (red-cone) species. In addition, we provide strong phylogenetic evidence for three distinct species (J. badia, J. conferta, J. lutchuensis) previously considered subspecies or varieties, as well as for the differentiation between the eastern and western Mediterranean lineages of J. macrocarpa. Our findings suggest that the Mediterranean basin was the primary center of diversification for Juniperus sect. Juniperus, followed by an East Asian-Tethyan disjunction resulting from uplifts of the Qinghai-Tibetan Plateau and climatic shifts. The colonization history of Macaronesia by red-cone junipers from the western Mediterranean appears to have taken place independently in two different geological periods: the Miocene (Azores) and the Pliocene (Madeira-Canary Islands). Overall, genomic data and phylogenetic analysis are key to consider a new taxonomic proposal and reconstruct the biogeographical history of the iconic needle-leaved junipers across the Paleartic.

Graphical modeling of additive color mixing. Analyses of electromagnetic effects as colors of the vision analyzer

The human visual analyzer is a high form of evolution. Some jellyfish can distinguish light and dark objects with sensitive cells. Squids, octopuses, and nautiluses from Cephalopods family have eyes with which they can see objects. Visual information is processed in the brain. In fishes, the visual analyzer evolved. Fishes living below 100 m depth inhabit a world with blue light. The authors consider the evolution of vision in these fishes due to the lowest absorption of blue and violet colors of electromagnetic waves from the optical spectrum. Subsequently, on land, in humans vision evolved towards the green color. Green is the most prevalent color on the land. In humans, three light-sensitive cones evolved – S, M, and L. S cones are most sensitive to blue, M – to green, and L – to red color in the spectrum. Some humans retain sensitivity of S to genetic changes and disorders. Additive color mi­xing is a high form of color perception in humans. The additive mixing of different colors achieves a new color in the human visual analyzer. Remarkably, different individuals perceive observed images in varying manners. Mixing neighboring colors on the spectrum gives one, two, or three colors. This process is estimated using graphical modeling. The graphical modeling with two colors allows for the creation of additive colors. One, two, or three additive colors can be obtained. The production of colors results from the light sensitivity of S, M, and L cones. An analysis that phy­sically demonstrates the mixing of green and red colors, resulting in the colors yellow or orange. When blue and red are mixed, the resulting colors are green, yellow, and orange is proposed. The additive mixing of blue and yellow gives green. The subjective nature of visual perception, influenced by the viewer’s heightened sensitivity to one of the colors, beco­mes evident in the presence of two colors. Notably, when the background is violet, the sensitivity of the blue cones diminishes.

S-cone contribution to oscillatory potentials in patients with blue cone monochromacy

PurposeThe aim of this exploratory study is to investigate the role of S-cones in oscillatory potentials (OPs) generation by individuals with blue-cone monochromacy (BCM), retaining S-cones, and achromatopsia (ACHM), lacking cone functions.MethodsThis retrospective study analyzed data from 39 ACHM patients, 20 BCM patients, and 26 controls. Central foveal thickness was obtained using spectral-domain optical coherence tomography, while amplitude and implicit time (IT) of a- and b-waves were extracted from the ISCEV Standard dark-adapted 3 cd.s.m−2 full-field ERG (ffERG). Time–frequency analysis of the same measurement enabled the extraction of OPs, providing insights into the dynamic characteristics of the recorded signal.ResultsBoth ACHM and BCM groups showed a significant reduction (p < .00001) of a- and b-wave amplitudes and ITs as well as the power of the OPs compared to the control groups. The comparison between ACHM and BCM didn’t show any statistically significant differences in the electrophysiological parameters. The analysis of covariance revealed significantly reduced central foveal thickness in the BCM group compared to ACHM and controls (p < .00001), and in ACHM compared to controls (p < .00001), after age correction and Tukey post-hoc analysis.ConclusionsS-cones do not significantly influence OPs, and the decline in OPs' power is not solely due to a reduced a-wave. This suggests a complex non-linear network influenced by photoreceptor inputs. Morphological changes don’t correlate directly with functional alterations, prompting further exploration of OPs’ function and physiological role.

Expression of red/green-cone opsin mutants K82E, P187S, M273K result in unique pathobiological perturbations to cone structure and function.

Long-and middle-wavelength cone photoreceptors, which are responsible for our visual acuity and color vision, comprise ~95% of our total cone population and are concentrated in the fovea of our retina. Previously, we characterized the disease mechanisms of the L/M-cone opsin missense mutations N94K, W177R, P307L, R330Q and G338E, all of which are associated with congenital blue cone monochromacy (BCM) or color-vision deficiency. Here, we used a similar viral vector-based gene delivery approach in M-opsin knockout mice to investigate the pathogenic consequences of the BCM or color-vision deficient associated L-cone opsin (OPN1LW) mutants K82E, P187S, and M273K. We investigated their subcellular localization, the pathogenic effects on cone structure, function, and cone viability. K82E mutants were detected predominately in cone outer segments, and its expression partially restored expression and correct localization of cone PDE6α' and cone transducin γ. As a result, K82E also demonstrated the ability to mediate cone light responses. In contrast, expression of P187S was minimally detected by either western blot or by immunohistochemistry, probably due to efficient degradation of the mutant protein. M273K cone opsin appeared to be misfolded as it was primarily localized to the cone inner segment and endoplasmic reticulum. Additionally, M273K did not restore the expression of cone PDE6α' and cone transducin γ in dorsal cone OS, presumably by its inability to bind 11-cis retinal. Consistent with the observed expression pattern, P187S and M273K cone opsin mutants were unable to mediate light responses. Moreover, expression of K82E, P187S, and M273K mutants reduced cone viability. Due to the distinct expression patterns and phenotypic differences of these mutants observed in vivo, we suggest that the pathobiological mechanisms of these mutants are distinct.

Structural and functional rescue of cones carrying the most common cone opsin C203R missense mutation.

An arginine to cysteine substitution at amino acid position 203 (C203R) is the most common missense mutation in human cone opsin. Linked to color blindness and blue cone monochromacy (BCM), C203 is involved in a crucial disulfide bond required for proper folding. It has previously been postulated that expression of mutant C203R cone opsin exerts a toxic effect on cone photoreceptors, similar to some well-characterized missense mutations in rhodopsin that lead to protein misfolding. In this study, we generated and characterized a BCM mouse model carrying the equivalent C203R mutation (Opn1mwC198R Opn1sw-/-) to investigate the disease mechanism and develop a gene therapy approach for this disorder. Untreated Opn1mwC198R Opn1sw-/- cones phenocopied affected cones in human patients with the equivalent mutation, exhibiting shortened or absent cone outer segments and loss of function. We determined that gene augmentation targeting cones specifically yielded robust rescue of cone function and structure when Opn1mwC198R Opn1sw-/- mice were treated at early ages. Importantly, treated cones displayed elaborated outer segments and replenished expression of crucial cone phototransduction proteins. Interestingly, we were unable to detect OPN1MWC198R mutant opsin at any age. We believe this is the first proof-of-concept study exploring the efficacy of gene therapy in BCM associated with a C203R mutation.

Ancestral photoreceptor diversity as the basis of visual behaviour.

Animal colour vision is based on comparing signals from different photoreceptors. It is generally assumed that processing different spectral types of photoreceptor mainly serves colour vision. Here I propose instead that photoreceptors are parallel feature channels that differentially support visual-motor programmes like motion vision behaviours, prey capture and predator evasion. Colour vision may have emerged as a secondary benefit of these circuits, which originally helped aquatic vertebrates to visually navigate and segment their underwater world. Specifically, I suggest that ancestral vertebrate vision was built around three main systems, including a high-resolution general purpose greyscale system based on ancestral red cones and rods to mediate visual body stabilization and navigation, a high-sensitivity specialized foreground system based on ancestral ultraviolet cones to mediate threat detection and prey capture, and a net-suppressive system based on ancestral green and blue cones for regulating red/rod and ultraviolet circuits. This ancestral strategy probably still underpins vision today, and different vertebrate lineages have since adapted their original photoreceptor circuits to suit their diverse visual ecologies.

Retinoic acid signaling regulates spatiotemporal specification of human green and red cones.

Trichromacy is unique to primates among placental mammals, enabled by blue (short/S), green (medium/M), and red (long/L) cones. In humans, great apes, and Old World monkeys, cones make a poorly understood choice between M and L cone subtype fates. To determine mechanisms specifying M and L cones, we developed an approach to visualize expression of the highly similar M- and L-opsin mRNAs. M-opsin was observed before L-opsin expression during early human eye development, suggesting that M cones are generated before L cones. In adult human tissue, the early-developing central retina contained a mix of M and L cones compared to the late-developing peripheral region, which contained a high proportion of L cones. Retinoic acid (RA)-synthesizing enzymes are highly expressed early in retinal development. High RA signaling early was sufficient to promote M cone fate and suppress L cone fate in retinal organoids. Across a human population sample, natural variation in the ratios of M and L cone subtypes was associated with a noncoding polymorphism in the NR2F2 gene, a mediator of RA signaling. Our data suggest that RA promotes M cone fate early in development to generate the pattern of M and L cones across the human retina.

Graphical modeling of additive color mixing. Perception of objects with different color shades for different observers.

Aim: To research subjective perceptions in additive color mixing. Materials and Methods: 79 individuals were surveyed, and they determined the colors they perceived in two photographs. The results of color mixing were determined using statistical analysis, graphical modeling, and Python program figures. Results: A new color is obtained by additive mixing monochromatic colors. Interestingly, different individuals perceive observed images in different ways. Mixing neighboring colors on the spectrum and those in different produces various visual effects. Distinction was found in the physical mixing of beams with different colors. Visual perception in the presence of two is subjective and is determined by the viewer's greater to one of the colors. Due to additive color mixing, additional parts of objects may appear golden or orange when there is a yellow color in a picture with blue tones. When the background is violet, the sensitivity of the blue cones decreases. Conclusions: An experiment involving the observation of color photographs established that individuals who perceive orange-violet snow do not perceive the blue color in the dress. The analysis revealed that yellow light activates the green and red cones. In contrast, blue light activates the blue cones in the retina, highlighting the importance of cone activation of color perception. The contrast between yellow and blue can create a visual ef f ect where parts of objects appear more pronounced or have more intense color, demonstrating the brain's processing of contrasting colors. The experiment also indicated a reduction in blue cone sensitivity with a violet background, illustrating chromatic adaptation. Different individuals may perceive colors differently based on background and lighting conditions, underscoring the subjectivity of visual perception. Finally, there is a debate over the dress's color perception. These fi ndings suggest that individuals working on media products can enhance image quality by considering additive color blending and background effects.

How does the blue ring form in a blue whirl: An experimental study

This paper presents an experimental study on the flame and flow structures of the blue whirl, in pursuit of an understanding of the blue ring's formation. The flame front was identified based on the OH* chemiluminescence signal and the flow field was obtained using high-frequency particle image velocimetry (PIV). The flame and flow field reveals the presence of a radial-inward boundary layer and the corner flow lifting the blue whirl. In the case of turbulent blue whirl, a discernible recirculation zone manifests within the flame, which offers direct evidence supporting the dominance of the vortex breakdown in blue whirl's formation. Furthermore, we find that the blue whirl's cone angle approximately equals the angle of the zero-vorticity line of the flow field, whereas the height of the blue ring aligns with the height of the upward deflection point on the radial-stagnation line. These findings demonstrate a strong coupling between the flame structures and the flow field. To understand the formation mechanism of the blue ring, the flow flux across the radial-stagnation line is calculated to estimate the equivalence ratio of the mixture forming the blue ring. It reveals that the blue ring is formed where the stoichiometric reaction occurs. This happens as the corner flow induces a strong shear to facilitate the mixing within the air-fuel mixture, causing the inner layer of the mixture to be diluted to the equivalence ratio of approximately 1 at the blue ring's location.

The hereditary abnormalities and genetic therapy of BCM

Blue cone monochromia is a visual disorder caused by genetic mutation, which is a single gene genetic disease thus very suitable for gene therapy. With this technique, mutations in patients' opsin genes can be repaired, thereby restoring their visual recognition of red and green. Compared with traditional treatment methods, gene therapy has obvious advantages in improving curative effect and is expected to achieve a radical cure of the disease. However, gene therapy still faces some challenges and limitations, such as technical validation, cost and accessibility issues. This review focuses on the progress of gene diagnosis and treatment technology in recent years and its application to blue cone monochromatic diseases. Further research and clinical practice will show more support and validation for the development of this treatment, thus providing patients with better treatment options.

Poster Session II: Non-degenerating double cone opsin knockout mouse model of blue cone monochromacy.

Ma et al. (2022) performed opsin gene therapy in a mouse model of blue cone monochromacy (BCM). Treatment was only effective for young animals because the retina degenerated, with a significant reduction in the number viable cones by 3 months. Their mouse was created by mating an Opn1mw knockout with a gene trap inserted in intron 2 of the Opn1mw gene, to an Opn1sw knockout with the neomycin resistance gene inserted in intron 3 of the Opn1sw gene. The Opn1mw knockout was reported as having "greatly reduced" M opsin expression, while the Opn1sw knockout was a severely hypomorphic allele. Their double opsin gene knockout (DKO) mouse is not a good model of BCM, which is typically a stationary disorder with no cone degeneration. We evaluated Opn1mw Opn1sw DKO mice for cone degeneration; these mice were created by Regeneron by deleting both genes using genome editing. Eyes of 1 year old DKO animals were processed for cryosections. Sections were immunostained using antibodies against a variety of cone proteins (S and M opsins, arrestin) and markers for retinal degeneration, then confocal imaged. Despite the absence of both cone opsins, cones remain viable and morphologically normal, and the retina shows no signs of degeneration at 1 year. This DKO mouse model will be a valuable tool for developing gene therapies targeting cone opsins, and also for understanding color vision circuitry in the retina.

Dye coupling of horizontal cells in the primate retina.

In the monkey retina, there are two distinct types of axon-bearing horizontal cells, known as H1 and H2 horizontal cells (HCs). In this study, cell bodies were prelabled using 4',6-diamidino-2-phenylindole (DAPI), and both H1 and H2 horizontal cells were filled with Neurobiotin™ to reveal their coupling, cellular details, and photoreceptor contacts. The confocal analysis of H1 and H2 HCs was used to assess the colocalization of terminal dendrites with glutamate receptors at cone pedicles. After filling H1 somas, a large coupled mosaic of H1 cells was labeled. The dendritic terminals of H1 cells contacted red/green cone pedicles, with the occasional sparse contact with blue cone pedicles observed. The H2 cells were also dye-coupled. They had larger dendritic fields and lower densities. The dendritic terminals of H2 cells preferentially contacted blue cone pedicles, but additional contacts with nearly all cones within the dendritic field were still observed. The red/green cones constitute 99% of the input to H1 HCs, whereas H2 HCs receive a more balanced input, which is composed of 58% red/green cones and 42% blue cones. These observations confirm those made in earlier studies on primate horizontal cells by Dacey and Goodchild in 1996. Both H1 and H2 HCs were axon-bearing. H1 axon terminals (H1 ATs) were independently coupled and contacted rod spherules exclusively. In contrast, the H2 axon terminals contacted cones, with some preference for blue cone pedicles, as reported by Chan and Grünert in 1998. The primate retina contains three independently coupled HC networks in the outer plexiform layer (OPL), identified as H1 and H2 somatic dendrites, and H1 ATs. At each cone pedicle, the colocalization of both H1 and H2 dendritic tips with GluA4 subunits close to the cone synaptic ribbons indicates that glutamate signaling from the cones to H1 and H2 horizontal cells is mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors.

Development of polymeric blue prosthetic retina photoreceptors

Two conjugated polymers with absorption spectra like that of human short-wavelength photoreceptors, or blue cones, are characterised to act as essential components of a sub-retinal flexible prototype prothesis for people suffering from retinal disease affecting photoreceptor cells. Spectrophotometric and transient tests undertaken in unbiased photovoltaic mode in ambient conditions demonstrate that the addition of hole-blocking ZnO layer results in reliably forcing a favourable capacitive charging regime and acts to improve the photoresponse over ten times in one polymer and 45 times in another. We report that the addition of fullerene and non-fullerene acceptor molecules in bulk-heterojunction (BHJ)-active layers make an almost sevenfold measured improvement to extracellular photovoltage for devices operating in an electrolyte environment.Graphical abstract

Retina-inspired narrowband perovskite sensor array for panchromatic imaging.

The retina is the essential part of the human visual system that receives light, converts it to neural signal, and transmits to brain for visual recognition. The red, green, and blue (R/G/B) cone retina cells are natural narrowband photodetectors (PDs) sensitive to R/G/B lights. Connecting with these cone cells, a multilayer neuro-network in the retina provides neuromorphic preprocessing before transmitting to brain. Inspired by this sophistication, we develop the narrowband (NB) imaging sensor combining R/G/B perovskite NB sensor array (mimicking the R/G/B photoreceptors) with a neuromorphic algorithm (mimicking the intermediate neural network) for high-fidelity panchromatic imaging. Compared to commercial sensors, we use perovskite "intrinsic" NB PD to exempt the complex optical filter array. In addition, we use an asymmetric device configuration to collect photocurrent without external bias, enabling a power-free photodetection feature. These results display a promising design for efficient and intelligent panchromatic imaging.

Blue cone monochromacy and gene therapy

Blue cone monochromacy (BCM) is a congenital vision disorder characterized by complete loss or severely reduced long- and middle-wavelength cone function, caused by mutations in the OPN1LW/OPN1MW gene cluster on the X-chromosome. BCM patients typically suffer from poor visual acuity, severely impaired color discrimination, myopia, and nystagmus. In this review, we cover the genetic causes of BCM, clinical features of BCM patients, genetic testing, and clinical outcome measurements for future BCM clinical trials. However, our emphasis is on detailing the animal models for BCM and gene therapy using adeno-associated vectors (AAV). We describe two mouse models resembling the two most common causes of BCM, current progress in proof-of-concept studies to treat BCM with deletion mutations, the challenges we face, and future directions.

A new method to quantify the human visual threshold from melanopsin sensitive ganglion cells.

Traditional photoreceptors utilize the chromophore retinal to absorb light coupled with a unique opsin protein to specify receptor spectral sensitivity. Light absorption triggers a cascade of events transducing light energy to neural signals beginning with graded potentials in receptors (rods and cones) and bipolar cells in outer and middle retina eventuating in action potentials at the inner retinal amacrine and ganglion cell levels. Unlike traditional photoreceptors, ganglion cells in the inner retina (intrinsically photosensitive retinal ganglion cells, ipRGCs) absorb short wavelength, blue light utilizing their photopigment melanopsin. Assessment across multiple species show that the ipRGCs mediate myriad visual and non-visual functions including photo-entrainment and circadian rhythms, the pupillary light reflex, sleep, alertness, cognition, mood, and even conscious visual perception. Some ipRGC functions can persist despite blindness in animal models and humans exemplifying their multidisciplinary control of visual and non-visual functions. In previous research we used selective chromatic adaptation (blue stimulus on a bright amber field) to suppress input from rods, red and green sensitive cones to identify retinal and cortical responses from ipRGCs. Herein we used a similar approach, coupled with a filter to block input from blue sensitive cones, to develop a clinically expedient method to measure the full-field, putative visual threshold from human ipRGCs. This metric may expand our ability to detect, diagnose and monitor ocular and neurologic disease and provide a global retinal metric of ipRGCs as a potential outcome measure for studies using gene therapy to arrest and/or improve vision in hereditary retinal diseases.