A murine RP1 missense mutation causes protein mislocalization and slowly progressive photoreceptor degeneration

Outer Retinal Thickness Is Associated With Cognitive Function in Normal Aging to Intermediate Age-Related Macular Degeneration

Purpose

Research on Alzheimer's disease (AD) and precursor states demonstrates a thinner retinal nerve fiber layer (NFL) compared to age-similar controls. Because AD and age-related macular degeneration (AMD) both impact older adults and share risk factors, we asked if retinal layer thicknesses, including NFL, are associated with cognition in AMD.

Methods

Adults ≥ 70 years with normal retinal aging, early AMD, or intermediate AMD per Age-Related Eye Disease Study (AREDS) nine-step grading of color fundus photography were enrolled in a cross-sectional study. Optical coherence tomography (OCT) volumes underwent 11-line segmentation and adjustments by a trained operator. Evaluated thicknesses reflect the vertical organization of retinal neurons and two vascular watersheds: NFL, ganglion cell layer-inner plexiform layer complex (GCL-IPL), inner retina, outer retina (including retinal pigment epithelium-Bruch's membrane), and total retina. Thicknesses were area weighted to achieve mean thickness across the 6-mm-diameter Early Treatment of Diabetic Retinopathy Study (ETDRS) grid. Cognitive status was assessed by the National Institutes of Health Toolbox cognitive battery for fluid and crystallized cognition. Correlations estimated associations between cognition and thicknesses, adjusting for age.

Results

Based on 63 subjects (21 per group), thinning of the outer retina was significantly correlated with lower cognition scores (P < 0.05). No other retinal thickness variables were associated with cognition.

Conclusions

Only the outer retina (photoreceptors, supporting glia, retinal pigment epithelium, Bruch's membrane) is associated with cognition in aging to intermediate AMD; NFL was not associated with cognition, contrary to AD-associated condition reports. Early and intermediate AMD constitute a retinal disease whose earliest, primary impact is in the outer retina. Our findings hint at a unique impact on the brain from the outer retina in persons with AMD.

A mouse model of cone photoreceptor function loss (cpfl9) with degeneration due to a mutation in Gucy2e

During routine screening of mouse strains and stocks by the Eye Mutant Resource at The Jackson Laboratory for genetic mouse models of human ocular disorders, we identified cpfl9, a mouse model with cone photoreceptor function loss. The mice exhibited an early-onset phenotype that was easily recognized by the absence of a cone-mediated b-wave electroretinography response and by a reduction in rod-mediated photoresponses at four weeks of age. By genetic mapping and high-throughput sequencing of a whole exome capture library of cpfl9, a homozygous 25 bp deletion within exon 11 of the Gucy2e gene was identified, which is predicted to result in a frame shift leading to premature termination. The corresponding protein in human, retinal guanylate cyclase 1 (GUCY2D), plays an important role in rod and cone photoreceptor cell function. Loss-of-function mutations in human GUCY2D cause LCA1, one of the most common forms of Leber congenital amaurosis, which results in blindness at birth or in early childhood. The early loss of cone and reduced rod photoreceptor cell function in the cpfl9 mutant is accompanied by a later, progressive loss of cone and rod photoreceptor cells, which may be relevant to understanding disease pathology in a subset of LCA1 patients and in individuals with cone-rod dystrophy caused by recessive GUCY2D variants. cpfl9 mice will be useful for studying the role of Gucy2e in the retina.

A defective structural zipper in photoreceptors causes inherited blindness

This Primer explores a PLOS Biology study which uses ultrastructure expansion microscopy to study the inner scaffold of the photoreceptor connecting cilium, the location of multiple proteins implicated in inherited forms of progressive sight loss such as retinitis pigmentosa and Leber congenital amaurosis.

Role of Optical Coherence Tomography in Identifying Retinal Biomarkers in Frontotemporal Dementia: A Review

Purpose of Review

Frontotemporal dementia (FTD) is often misdiagnosed or recognized late. Clinical heterogeneity and overlap with other dementias impede accurate diagnosis. FTD biomarkers are limited, expensive, and invasive. We present a narrative review of the current literature focused on optical coherence tomography (OCT) to identify retinal biomarkers of dementia, discuss OCT findings in FTD, and explore the implications of an FTD-specific ocular biomarker for research and patient care.

Recent Findings

Recent studies suggest that outer retinal thinning detected via OCT may function as a novel ocular biomarker of FTD. The degree and rate of inner retinal thinning may correlate with disease severity and progression. In Alzheimer disease (AD), OCT demonstrates thinning of the inner retina, which may differentiate this condition from FTD. We conducted a comprehensive search of the literature and reviewed published OCT findings in FTD, AD, and mild cognitive impairment, as well as reports on biomarkers of FTD and AD used in the research and patient care settings. Three of the authors (O.M., N.S.K., and K.Z.Y.) independently conducted literature searches using PubMed to identify studies published before May 1, 2020, using the following search terminology: "Alzheimer's disease," "Alzheimer's dementia," "frontotemporal dementia," "FTD," "mild cognitive impairment," "dementia biomarkers," and "neurodegeneration biomarkers." Search results were then refined using one or more of the following keywords: "optical coherence tomography," "optical coherence tomography angiography," "retinal imaging," and "retinal thinning." The selection of published works for inclusion in this narrative review was then limited to full-text articles written in English based on consensus agreement of the authors.

Summary

FTD diagnosis is imprecise, emphasizing the need for improved state and trait biomarkers. OCT imaging of the retina holds considerable potential for establishing effective ocular biomarkers for FTD.

Biallelic RP1-associated retinal dystrophies: Expanding the mutational and clinical spectrum

PURPOSE

To evaluate the phenotypic spectrum of autosomal recessive RP1-associated retinal dystrophies and assess genotypic associations.

METHODS

A retrospective multicenter study was performed of patients with biallelic RP1-associated retinal dystrophies. Data including presenting symptoms and age, visual acuity, kinetic perimetry, full field electroretinogram, fundus examination, multimodal retinal imaging, and RP1 genotype were evaluated.

RESULTS

Nineteen eligible patients from 17 families were identified and ranged in age from 10 to 56 years at the most recent evaluation. Ten of the 21 unique RP1 variants identified were novel, and mutations within exon 2 accounted for nearly half of alleles across the cohort. Patients had clinical diagnoses of retinitis pigmentosa (13), cone-rod dystrophy (3), Leber congenital amaurosis (1), early-onset severe retinal dystrophy (1), and macular dystrophy (1). Macular atrophy was a common feature across the cohort. Symptom onset occurred between 4 and 30 years of age (mean 14.9 years, median 13 years), but there were clusters of onset age that correlated with the effects of RP1 mutations at a protein level. Patients with later-onset disease, including retinitis pigmentosa, had at least one missense variant in an exon 2 DCX domain.

CONCLUSIONS

Biallelic RP1 mutations cause a broad spectrum of retinal disease. Exon 2 missense mutations are a significant contributor to disease and can be associated with a considerably later onset of retinitis pigmentosa than that typically associated with biallelic RP1 mutations.

Forward genetic analysis using OCT screening identifies Sfxn3 mutations leading to progressive outer retinal degeneration in mice

Retinal disease and loss of vision can result from any disruption of the complex pathways controlling retinal development and homeostasis. Forward genetics provides an excellent tool to find, in an unbiased manner, genes that are essential to these processes. Using N-ethyl-N-nitrosourea mutagenesis in mice in combination with a screening protocol using optical coherence tomography (OCT) and automated meiotic mapping, we identified 11 mutations presumably causative of retinal phenotypes in genes previously known to be essential for retinal integrity. In addition, we found multiple statistically significant gene-phenotype associations that have not been reported previously and decided to target one of these genes, Sfxn3 (encoding sideroflexin-3), using CRISPR/Cas9 technology. We demonstrate, using OCT, light microscopy, and electroretinography, that two Sfxn3 ^-/- mouse lines developed progressive and severe outer retinal degeneration. Electron microscopy showed thinning of the retinal pigment epithelium and disruption of the external limiting membrane. Using single-cell RNA sequencing of retinal cells isolated from C57BL/6J mice, we demonstrate that Sfxn3 is expressed in several bipolar cell subtypes, retinal ganglion cells, and some amacrine cell subtypes but not significantly in Müller cells or photoreceptors. In situ hybridization confirmed these findings. Furthermore, pathway analysis suggests that Sfxn3 may be associated with synaptic homeostasis. Importantly, electron microscopy analysis showed disruption of synapses and synaptic ribbons in the outer plexiform layer of Sfxn3 ^-/- mice. Our work describes a previously unknown requirement for Sfxn3 in retinal function.

Reduced expression of the nob8 gene does not normalize the distribution or function of mGluR6 in the mouse retina

Purpose

The Grm6nob8 mouse carries a missense mutation in the Grm6 gene (p.Met66Leu), and exhibits a reduced b-wave of the electroretinogram (ERG), abnormal localization of metabotropic glutamate receptor 6 (mGluR6) to the depolarizing bipolar cell (DBC) soma, and a reduced level of mGluR6 at the DBC dendritic tips. Although the underlying mechanism remains unknown, one possible explanation is that DBCs cannot efficiently traffic the mutant mGluR6. In that scenario, reducing the total amount of mutant mGluR6 protein might normalize localization, and thus, improve the ERG phenotype as well. The second purpose of this study was to determine whether the abnormal cellular distribution of mutant mGluR6 in Grm6nob8 retinas might induce late onset DBC degeneration.

Methods

We crossed Grm6nob8 animals with Grm6nob3 mice, which carry a null mutation in Grm6, to generate Grm6nob3/nob8 compound heterozygotes. We used western blotting to measure the total mGluR6 content, and immunohistochemistry to document mGluR6 localization within DBCs. In addition, we examined outer retinal function with ERG and retinal architecture in vivo with spectral domain optical coherence tomography (SD-OCT).

Results

The retinal content of mGluR6 was reduced in the retinas of the Grm6nob3/nob8 compound heterozygotes compared to the Grm6nob8 homozygotes. The cellular distribution of mGluR6 in the Grm6nob3/nob8 compound heterozygotes matched that of the Grm6nob8 homozygotes, with extensive expression throughout the DBC cell body and limited expression at the DBC dendritic tips. The dark-adapted ERG b-waves of the Grm6nob3/nob8 mice were reduced in comparison to those of the Grm6nob8 homozygotes at postnatal day 21 and 28. The overall ERG waveforms obtained from 4- through 68-week old Grm6nob8 mice were in general agreement for dark- and light-adapted conditions. The maximum response and sensitivity of the dark-adapted ERG b-wave did not change statistically significantly with age. SD-OCT revealed the maintained laminar structure of the retina, including a clear inner nuclear layer (INL) at each age examined (from 11 to 57 weeks old), although the INL in the mice older than 39 weeks of age was somewhat thinner than that seen at 11 weeks.

Conclusions

Mislocalization of mutant mGluR6 is not normalized by reducing the total mGluR6. Mislocalized mutant mGluR6 does not trigger substantial loss of DBCs.

Functional Genomics of the Retina to Elucidate its Construction and Deconstruction

The retina is the light sensitive part of the eye and nervous tissue that have been used extensively to characterize the function of the central nervous system. The retina has a central position both in fundamental biology and in the physiopathology of neurodegenerative diseases. We address the contribution of functional genomics to the understanding of retinal biology by reviewing key events in their historical perspective as an introduction to major findings that were obtained through the study of the retina using genomics, transcriptomics and proteomics. We illustrate our purpose by showing that most of the genes of interest for retinal development and those involved in inherited retinal degenerations have a restricted expression to the retina and most particularly to photoreceptors cells. We show that the exponential growth of data generated by functional genomics is a future challenge not only in terms of storage but also in terms of accessibility to the scientific community of retinal biologists in the future. Finally, we emphasize on novel perspectives that emerge from the development of redox-proteomics, the new frontier in retinal biology.

Expanding the retinal phenotype of RP1: from retinitis pigmentosa to a novel and singular macular dystrophy

PURPOSE

This study aimed to identify the underlying genetic cause(s) of inherited retinal dystrophy (IRD) in 12 families of Kuwaiti origin affected by macular dystrophy and four Spanish patients affected by retinitis pigmentosa (RP).

METHODS

Clinical diagnoses were based on standard ophthalmic evaluations (best-corrected visual acuity, retinography, fundus autofluorescence imaging, optical coherence tomography, electroretinography and visual field tests). Panel-based whole exome sequencing was used to simultaneously analyse 224 IRD genes in one affected member of each family. The putative causative variants were confirmed by Sanger sequencing and cosegregation analyses. Haplotype analysis was performed using single nucleotide polymorphisms.

RESULTS

A homozygous missense mutation c.606C>A (p.Asp202Glu) in RP1 was found to be the molecular cause of IRD in all 12 families from Kuwait. These patients exhibited comparable symptoms, including progressive decline in visual acuity since adolescence. Fundus autofluorescence images revealed bilateral macular retinal pigment epithelium disturbances, with neither perimacular flecks nor peripheral alterations. A shared haplotype spanning at least 1.1 Mb was identified in all families, suggesting a founder effect. Furthermore, RP1 variants involving nonsense and/or frameshifting mutations (three of them novel) were identified in three Spanish autosomal-recessive RP families and one dominant RP pedigree.

CONCLUSION

This study describes, for the first time, a macular dystrophy phenotype caused by an RP1 mutation; establishing a new genotype-phenotype correlation in this gene, expanding its mutation spectrum and further highlighting the clinical heterogeneity associated with IRD.

Persistent and Progressive Outer Retina Thinning in Frontotemporal Degeneration

OBJECTIVE

While Alzheimer's disease is associated with inner retina thinning measured by spectral-domain optical coherence tomography (SD-OCT), our previous cross-sectional study suggested outer retina thinning in frontotemporal degeneration (FTD) patients compared to controls without neurodegenerative disease; we sought to evaluate longitudinal changes of this potential biomarker.

METHODS

SD-OCT retinal layer thicknesses were measured at baseline and after 1-2 years. Clinical criteria, genetic analysis, and a cerebrospinal fluid biomarker (total tau: β-amyloid) to exclude likely underlying Alzheimer's disease pathology were used to define a subgroup of predicted molecular pathology (i.e., tauopathy). Retinal layer thicknesses and rates of change in all FTD patients (n = 16 patients, 30 eyes) and the tauopathy subgroup (n = 9 patients,16 eyes) were compared to controls (n = 30 controls, 47 eyes) using a generalized linear model accounting for inter-eye correlation and adjusting for age, sex, and race. Correlations between retinal layer thicknesses and Mini-Mental State Examinations (MMSE) were assessed.

RESULTS

Compared to controls, returning FTD patients (143 vs. 130 μm, p = 0.005) and the tauopathy subgroup (143 vs. 128 μm, p = 0.03) had thinner outer retinas but similar inner layer thicknesses. Compared to controls, the outer retina thinning rate was not significant for all FTD patients (p = 0.34), but was significant for the tauopathy subgroup (-3.9 vs. 0.4 μm/year, p = 0.03). Outer retina thickness change correlated with MMSE change in FTD patients (Spearman rho = 0.60, p = 0.02) and the tauopathy subgroup (rho = 0.73, p = 0.04).

CONCLUSION

Our finding of FTD outer retina thinning persists and longitudinally correlates with disease progression. These findings were especially seen in probable tauopathy patients, which showed progressive outer retina thinning.

Optical coherence tomography identifies outer retina thinning in frontotemporal degeneration

OBJECTIVE

Whereas Alzheimer disease (AD) is associated with inner retina thinning visualized by spectral-domain optical coherence tomography (SD-OCT), we sought to determine if the retina has a distinguishing biomarker for frontotemporal degeneration (FTD).

METHODS

Using a cross-sectional design, we examined retinal structure in 38 consecutively enrolled patients with FTD and 44 controls using a standard SD-OCT protocol. Retinal layers were segmented with the Iowa Reference Algorithm. Subgroups of highly predictive molecular pathology (tauopathy, TAR DNA-binding protein 43, unknown) were determined by clinical criteria, genetic markers, and a CSF biomarker (total tau: β-amyloid) to exclude presumed AD. We excluded eyes with poor image quality or confounding diseases. SD-OCT measures of patients (n = 46 eyes) and controls (n = 69 eyes) were compared using a generalized linear model accounting for intereye correlation, and correlations between retinal layer thicknesses and Mini-Mental State Examination (MMSE) were evaluated.

RESULTS

Adjusting for age, sex, and race, patients with FTD had a thinner outer retina than controls (132 vs 142 μm, p = 0.004). Patients with FTD also had a thinner outer nuclear layer (ONL) (88.5 vs 97.9 μm, p = 0.003) and ellipsoid zone (EZ) (14.5 vs 15.1 μm, p = 0.009) than controls, but had similar thicknesses for inner retinal layers. The outer retina thickness of patients correlated with MMSE (Spearman r = 0.44, p = 0.03). The highly predictive tauopathy subgroup (n = 31 eyes) also had a thinner ONL (88.7 vs 97.4 μm, p = 0.01) and EZ (14.4 vs 15.1 μm, p = 0.01) than controls.

CONCLUSIONS

FTD is associated with outer retina thinning, and this thinning correlates with disease severity.

Intraperitoneal injection of (-)-Epigallocatechin-3-gallate protects against light-induced photoreceptor degeneration in the mouse retina

PURPOSE

(-)-epigallocatechin-3-gallate (EGCG), a major catechin component of green tea, is reported to delay or prevent certain forms of cancer, arthritis, cardiovascular disease, and neurodegenerative disorders. In this study, we determined if systemically administered EGCG could protect the retina against light damage (LD) in mice.

METHODS

BALB/cJ mice were treated with either EGCG or saline via intraperitoneal (IP) injection, and then placed under constant cool white light-emitting diode (LED) light (10,000 lux) for 5 h. Retinal structure and function were evaluated using optical coherence tomography (OCT), histology, and electroretinography (ERG) 7 days after LD. In addition, the mRNAs of several oxidative stress genes were quantified by qPCR before LD and 24 h after LD.

RESULTS

OCT and photomicrographs of mouse retinas showed morphologic protection of photoreceptors. Mice in the EGCG group had significantly higher ERG amplitudes for all three wave types compared with mice in the saline control group, which indicated that EGCG protected retinal function. Furthermore, qPCR results showed that EGCG administration can increase the mRNA level of the antioxidant gene Sod2 before LD and 24 h after LD.

CONCLUSIONS

The IP injection of EGCG attenuated the detrimental effects of bright light on the retinas of BALB/cJ mice by protecting the structure and function of the retina.

OCT-Angiography for Non-Invasive Monitoring of Neuronal and Vascular Structure in Mouse Retina: Implication for Characterization of Retinal Neurovascular Coupling

PURPOSE

Optical coherence tomography angiography (OCT-A) is a newly developed technique to visualize retinal vasculature non-invasively based on interferometry. Although OCT-A has been used clinically, its applications in small animal studies have been limited. This study is designed to develop and demonstrate the feasibility of a protocol for the use of an en-face OCT-based method to visualize and quantify retinal microvasculature in mice that can be used for in vivo assessment of retina ischemia.

METHODS

A customized algorithm was developed to extract angiographic profiles of the mouse retina from en-face OCT using an unmodified Bioptigen Envisu R-Class OCT imaging system. En-face OCT images were collected in living animals and then compared to images acquired following termination of blood flow to the retina. The images were processed with ImageJ using the raw file importer. The vessel enhancement algorithm was developed based on a combination of local contrast enhancement, Laplacian of Gaussian peak detection and background subtraction methods. For comparison, fluorescein angiography (FA) was performed using Heidelberg Spectralis^® HRA+OCT imaging system.

RESULTS

By vessel enhancement algorithm, we successfully extracted retinal vasculature and quantified retinal vessel branch points, vascular area and vessel lengths with AngioTool. While the retinal neuronal structure could be simultaneously identified and quantified using B-scan and volumetric OCT run in the annular scanning model, the retinal vasculature in OCT-A was dramatically diminished after the animals were sacrificed, indicating en-face OCT-A signal is a measure of the blood flow.

CONCLUSIONS

These studies indicate that a novel approach to extract angiographs from en-face OCT images by utilizing local structure enhancement can be used to provide depth-resolved retinal vasculature distributions. Simultaneous non-invasive analysis of retinal vessels and neurons by OCT-A and OCT may provide a novel approach to characterize retinal ischemia accompanied by neurovascular coupling.

Hereditary Retinal Dystrophy

As our understanding of the genetic basis for inherited retinal disease has expanded, gene therapy has advanced into clinical development. When the gene mutations associated with inherited retinal dystrophies were identified, it became possible to create animal models in which individual gene were altered to match the human mutations. The retina of these animals were then characterized to assess whether the mutated genes produced retinal phenotypes characteristic of disease-affected patients. Following the identification of a subpopulation of patients with the affected gene and the development of techniques for the viral gene transduction of retinal cells, it has become possible to deliver a copy of the normal gene into the retinal sites of the mutated genes. When this was performed in animal models of monogenic diseases, at an early stage of retinal degeneration when the affected cells remained viable, successful gene augmentation corrected the structural and functional lesions characteristic of the specific diseases in the areas of the retina that were successfully transduced. These studies provided the essential proof-of-concept needed to advance monogenic gene therapies into clinic development; these therapies include treatments for: Leber's congenital amaurosis type 2, caused by mutations to RPE65, retinoid isomerohydrolase; choroideremia, caused by mutations to REP1, Rab escort protein 1; autosomal recessive Stargardt disease, caused by mutations to ABCA4, the photoreceptor-specific ATP-binding transporter; Usher 1B disease caused by mutations to MYO7A, myosin heavy chain 7; X-linked juvenile retinoschisis caused by mutations to RS1, retinoschisin; autosomal recessive retinitis pigmentosa caused by mutations to MERTK, the proto-oncogene tyrosine-protein kinase MER; Leber's hereditary optic neuropathy caused by mutations to ND4, mitochondrial nicotinamide adenine dinucleotide ubiquinone oxidoreductase (complex I) subunit 4 and achromatopsia, caused by mutations to CNGA3, cyclic nucleotide-gated channel alpha 3 and CNGB3, cyclic nucleotide-gated channel beta 3. This review includes a tabulated summary of treatments for these monogenic retinal dystrophies that have entered into clinical development, as well as a brief summary of the preclinical data that supported their advancement into clinical development.

Molecular basis for photoreceptor outer segment architecture

To serve vision, vertebrate rod and cone photoreceptors must detect photons, convert the light stimuli into cellular signals, and then convey the encoded information to downstream neurons. Rods and cones are sensory neurons that each rely on specialized ciliary organelles to detect light. These organelles, called outer segments, possess elaborate architectures that include many hundreds of light-sensitive membranous disks arrayed one atop another in precise register. These stacked disks capture light and initiate the chain of molecular and cellular events that underlie normal vision. Outer segment organization is challenged by an inherently dynamic nature; these organelles are subject to a renewal process that replaces a significant fraction of their disks (up to ∼10%) on a daily basis. In addition, a broad range of environmental and genetic insults can disrupt outer segment morphology to impair photoreceptor function and viability. In this chapter, we survey the major progress that has been made for understanding the molecular basis of outer segment architecture. We also discuss key aspects of organelle lipid and protein composition, and highlight distributions, interactions, and potential structural functions of key OS-resident molecules, including: kinesin-2, actin, RP1, prominin-1, protocadherin 21, peripherin-2/rds, rom-1, glutamic acid-rich proteins, and rhodopsin. Finally, we identify key knowledge gaps and challenges that remain for understanding how normal outer segment architecture is established and maintained.

Retinal Pre-Conditioning by CD59a Knockout Protects against Light-Induced Photoreceptor Degeneration

Complement dysregulation plays a key role in the pathogenesis of age-related macular degeneration (AMD), but the specific mechanisms are incompletely understood. Complement also potentiates retinal degeneration in the murine light damage model. To test the retinal function of CD59a, a complement inhibitor, CD59a knockout (KO) mice were used for light damage (LD) experiments. Retinal degeneration and function were compared in WT versus KO mice following light damage. Gene expression changes, endoplasmic reticulum (ER) stress, and glial cell activation were also compared. At baseline, the ERG responses and rhodopsin levels were lower in CD59aKO compared to wild-type (WT) mice. Following LD, the ERG responses were better preserved in CD59aKO compared to WT mice. Correspondingly, the number of photoreceptors was higher in CD59aKO retinas than WT controls after LD. Under normal light conditions, CD59aKO mice had higher levels than WT for GFAP immunostaining in Müller cells, mRNA and protein levels of two ER-stress markers, and neurotrophic factors. The reduction in photon capture, together with the neurotrophic factor upregulation, may explain the structural and functional protection against LD in the CD59aKO.

Berberine protects against light-induced photoreceptor degeneration in the mouse retina

Oxidative stress and inflammation play key roles in the light damage (LD) model of photoreceptor degeneration, as well as in age-related macular degeneration (AMD). We sought to investigate whether Berberine (BBR), an antioxidant herb extract, would protect the retina against light-induced degeneration. To accomplish this, Balb/c mice were treated with BBR or PBS via gavage for 7 days, and then were placed in constant cool white light-emitting diode (LED) light (10,000 lux) for 4 h. Retinal function and degeneration were evaluated by histology, electroretinography (ERG) and optical coherence tomography (OCT) at 7d after LD. Additionally, mRNA levels of cell-type specific, antioxidant, and inflammatory genes were compared 7d after LD. Photoreceptor DNA fragmentation was assessed via the terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) assay. LD resulted in substantial photoreceptor-specific cell death. Histological analysis using plastic sections showed dosing with BBR preserved photoreceptors. The ERG analysis demonstrated functional protection by BBR in rod-b, -a, and cone-b waves. In OCT images, mice receiving PBS showed severe thinning and disorganization of the photoreceptor layer 7 days after LD, whereas mice treated with BBR had significantly less thinning and disorganization. Consistent with OCT results, the mRNA levels of Rho in the NSR, and Rpe65 and Mct3 in the RPE, were significantly higher in mice treated with BBR. The numbers of TUNEL-positive photoreceptors were significantly decreased in BBR-treated mice. The retinal mRNA levels of oxidative stress genes, the number of microglia/macrophages, and the malondialdehyde (MDA) immunolabeling were significantly lower in BBR-treated mice compared to controls 48 h after LD, which indicates oxidative stress was reduced by BBR in light-damaged eyes. In conclusion, systemic BBR is protective against light-induced retinal degeneration associated with diminished oxidative stress in the retina. These results suggest that BBR may be protective against retinal diseases involving oxidative stress.