Flow cytometric method for the detection and quantification of retinal cell death and oxidative stress.

Retinal cell death is the major cause of vision loss in many forms of blinding retinal disease. A plethora of research is focused on understanding the mechanisms of retinal cell death to identify potential neuroprotective strategies that prevent vision loss in these diseases. Traditionally, histological techniques have been used to determine the type and extent of cell death in the retina. These techniques, such as TUNEL labeling and immunohistochemistry, are laborious and time consuming, resulting in low throughput and variable results depending on the experimenter. To increase throughput and reduce variability, we developed several flow cytometry-based assays to detect and quantify retinal cell death. The methods and accompanying data presented demonstrate that flow cytometry can readily detect both retinal cell death and oxidative stress and importantly, the efficacy of neuroprotective agents. These methods will be of interest to investigators looking to increase throughput and efficiency without compromising sensitivity as the methods herein reduce analysis time from several months to less than a week. As such, the flow cytometry methods presented have the potential to expedite research efforts focused on developing novel strategies for retinal cell neuroprotection.

Dark-reared rd10 mice experience rapid photoreceptor degeneration with short exposure to room-light during in vivo retinal imaging.

Inherited retinal diseases (IRDs) are a collection of rare genetic conditions, which can lead to complete blindness. A large number of causative genes have been identified for IRDs and while some success has been achieved with gene therapies, they are limited in scope to each individual gene and/or the specific mutation harbored by each patient with an IRD. Multiple studies are underway to elucidate common underlying mechanisms contributing to photoreceptor (PR) loss and to design gene-agnostic, pan-disease therapeutics. The rd10 mouse, which recapitulates slow degeneration of PRs, is an in vivo IRD model used commonly by vision researchers. Light deprivation by rearing animals in complete darkness significantly delays PR death in rd10 mice, subsequently increasing the time window for in vivo studies investigating neuroprotective strategies. Longitudinal in vivo retinal imaging following the same rd10 mice over time is a potential solution for reducing the number of animals required to complete a study. We describe a previously unreported phenotype in the dark-reared rd10 model that is characterized by dramatic PR degeneration following brief exposure to low-intensity light. This exquisite light sensitivity precludes the use of longitudinal studies employing in vivo imaging or other functional assessment requiring room light in rd10 mice and highlights the importance of closely following animal models of IRD to determine any deviations from the expected degeneration curve during routine experimentation.

Autophagy activation and photoreceptor survival in retinal detachment.

We assess the effect of autophagy inhibition on photoreceptor (PR) survival during experimental retinal detachment (RD) and examine the and examine the relationship between autophagy and the expression of glycolytic enzymes HK2 and PKM2 in the retina. We find that inhibiting autophagy by genetic knock out of the autophagy activator Atg5 in rod PRs resulted in increased apoptotic and necroptotic cell death during RD, demonstrated by elevated terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells, caspase 8 activity, transcript levels of Fas receptor and RIPK3 as compared to controls. The absence of autophagy in rods resulted in downregulation of hexokinase 2 and pyruvate kinase muscle isozyme 2 levels. More than 460 proteins were identified by mass spectroscopy in autophagosomes isolated from detached retinas compared with less than 150 proteins identified in autophagosomes from attached retinas. Among various cellular compartments, proteins from cytoskeleton, cytoplasm and intracellular organelles constituted a large portion of increased autophagosome contents. These proteins represent numerous biological processes, including phototransduction, cell-cell signaling, metabolism and inflammation. Our findings suggest that competent autophagy machinery is necessary for PR homeostasis and improving PR survival during periods of nutrient deprivation.

Retinal neuroprotection: current strategies and future directions.

PURPOSE OF REVIEW: Photoreceptor cell death is the ultimate cause of vision loss in many retinal disorders. Currently, there are no commercially available treatments to prevent photoreceptor cell loss and preserve vision, and there is a critical unmet need for neuroprotective modalities to improve photoreceptor survival in a multitude of retinal disorders. This review summarizes the literature published on this topic in the last 18 months. RECENT FINDINGS: A plethora of novel therapeutic modalities for photoreceptor neuroprotection have recently been examined in clinical trials for age-related macular degeneration, inherited retinal dystrophies, and macular telangiectasia type 2. These modalities include agents that target the complement pathway, stem cells, gene therapies, and neurotrophic factors. Additionally, improved understanding in the metabolic signals that regulate photoreceptor survival and function may ultimately identify targets for developing novel neuroprotective agents in a multitude of retinal disorders. SUMMARY: Retinal neuroprotection is the next frontier in ophthalmic disease, and the discovery of novel neuroprotective strategies will fill a critical unmet need. Although the clinical utility of existing neuroprotective therapies is still quite limited, we are cautiously optimistic in light of the recent successes described in this review as well as other promising developments.

Pharmacotherapies for Retinal Detachment.

Retinal detachment is an important cause of visual loss. Currently, surgical techniques, including vitrectomy, scleral buckle, and pneumatic retinopexy, are the only means to repair retinal detachment and restore vision. However, surgical failure rates may be as high as 20%, and visual outcomes continue to vary secondary to multiple processes, including postoperative cystoid macular edema, epiretinal membrane formation, macular folds, and, ultimately, photoreceptor death. Therefore, pharmacotherapies are being sought to aid the success rates of modern surgical techniques and reduce or slow the degeneration of photoreceptors during retinal detachment. This review discusses potential therapeutic avenues that aid in retinal reattachment, reduce the rate of retinal redetachment by limiting proliferative vitreoretinopathy, and protect against photoreceptor cell death.

Rates of Vitrectomy among Enrollees in a United States Managed Care Network, 2001-2012.

PURPOSE: To determine whether vitrectomy surgery rates have changed over the past decade and factors affecting the odds of undergoing this procedure. DESIGN: Retrospective, longitudinal cohort study. PARTICIPANTS: All enrollees 21 years of age or older between 2001 and 2012 in a United States managed care network. METHODS: Claims data from a managed care network were analyzed to identify all enrollees who underwent 1 vitrectomy or more each year from 2001 through 2012. Rates of vitrectomy per 1000 enrollees were computed each year from 2001 through 2012 for the entire group and separately for patients with and without diabetes mellitus. Multivariate logistic regression assessed factors affecting the odds of undergoing vitrectomy surgery. MAIN OUTCOME MEASURES: Annual rates of vitrectomy surgery from 2001 through 2012 and odds ratios (ORs) of undergoing a vitrectomy with 95% confidence intervals (CIs). RESULTS: Among the 11 161 907 eligible enrollees, 40 892 (0.4%) underwent vitrectomy over the 12-year period. The average age of those undergoing vitrectomy was 57±13 years. Overall vitrectomy rates increased 31% from 2001 to 2012 (from 1.47 to 1.92 per 1000 patients). During this same period, the vitrectomy rate among persons with diabetes mellitus decreased by 43% (from 5.84 to 3.31 per 1000 patients with diabetes). Women had 24% decreased odds of undergoing vitrectomy (adjusted odds ratio [OR], 0.76; 95% confidence interval [CI], 0.72-0.79). The odds of undergoing a vitrectomy were 17% greater for black persons (adjusted OR, 1.17; 95% CI, 1.07-1.27) and 7% higher for persons with diabetes (adjusted OR, 1.07; 95% CI, 1.01-1.14). CONCLUSIONS: Overall, we observed an increase in the vitrectomy rates per 1000 enrollees in this large managed care network over the course of the past decade. However, among persons with diabetes mellitus, vitrectomy rates declined substantially over this period. These changes may be explained, in part, by advances in surgical instrumentation and imaging methods to detect retinal diseases changing indications for surgery, improvements in diabetes care, and alternative treatment options for managing retinal conditions. These results may be useful for future planning of manpower needs and highlight the need for aggressive prevention of complications in black persons with diabetes.

Presbyopia: a pilot investigation of the barriers and benefits of near visual acuity correction among a rural Filipino population.

BACKGROUND: Presbyopia is the age-related decline in accommodation that diminishes the ability of the eye to focus on near objects. Presbyopia is common and easy to correct; however, many communities lack access to basic eye care. The purpose of this project was to assess the burden of uncorrected presbyopia in a rural Filipino population and to pilot an intervention aimed at increasing access to reading glasses in the community. METHODS: Individuals above the age of 40 who presented to a health outreach in the Philippines were invited to undergo a near vision exam to detect the presence of functional presbyopia and be fitted with ready-made, single-vision glasses. The change in stereoacuity was used as a surrogate measure of functional improvement after near vision correction. A questionnaire was administered to assess this population's perceived barriers and benefits to correcting near vision. RESULTS: The average age of the participants was 57 ± 11 years, with 87.6% of participants having an uncorrected near visual acuity of <20/50. Reading glasses improved near vision to 20/40 or better in 77.7% of participants having near-vision impairment (uncorrected near visual acuity of <20/40). Over 75% of participants also showed improvement in stereoacuity. Cost, rather than availability, was perceived to be the greater barrier to the procurement of glasses, and 84% of participants reported that the glasses dispensed would greatly improve their ability to earn a living. CONCLUSIONS: Dispensing ready-made, single-vision glasses is a simple and cost-effective intervention to improve near vision and enhance depth perception. A greater understanding of the barriers and benefits to correcting near vision will inform the design and execution of a sustainable program to correct presbyopia in developing countries.

Posterior Uveitis in Ocular-Involving Chronic Lymphocytic Leukemia and the Utility of Negative MYD88 L265P Testing in the Diagnosis.

Introduction: The aim of this study was to investigate if a negative test result for MYD88 L265P mutation, associated with vitreoretinal lymphoma (VRL) and primary CNS lymphoma, in liquid biopsies from intraocular fluids can be a useful adjuvant test to diagnose chronic lymphocytic leukemia in clinically challenging cases. Case Presentations: We selected patients with a past medical history or examinations findings suspicious for intraocular lymphoma. We evaluated both vitreous and aqueous humor-derived (AHD) MYD88 L265P mutation from patients that had suspected intraocular lymphoma that warranted a liquid biopsy procedure. Gold-standard cytopathology, flow cytometry, and gene rearrangement studies were also performed. All 4 patients had negative AHD MYD88 L265P mutation testing. Gold-standard testing (cytology) either showed paucicellular specimens (1/4) or specimens with high background inflammation (3/4). One case showed a rare B-cell clonal population (CD5+, Kappa-restricted by flow cytometry), but this was not sufficient to make any definitive diagnosis. All patients were subsequently initiated on systemic therapy and had improvement in their disease burden. Conclusions: Negative AHD MYD88 L265P mutation testing can serve as an adjuvant molecular test to diagnose difficult cases of intraocular CLL.

Glutamine catabolism supports amino acid biosynthesis and suppresses the integrated stress response to promote photoreceptor survival.

Photoreceptor loss results in vision loss in many blinding diseases, and metabolic dysfunction underlies photoreceptor degeneration. So, exploiting photoreceptor metabolism is an attractive strategy to prevent vision loss. Yet, the metabolic pathways that maintain photoreceptor health remain largely unknown. Here, we investigated the dependence of photoreceptors on Gln catabolism. Gln is converted to glutamate via glutaminase (GLS), so mice lacking GLS in rod photoreceptors were generated to inhibit Gln catabolism. Loss of GLS produced rapid rod photoreceptor degeneration. In vivo metabolomic methodologies and metabolic supplementation identified Gln catabolism as critical for glutamate and aspartate biosynthesis. Concordant with this amino acid deprivation, the integrated stress response (ISR) was activated with protein synthesis attenuation, and inhibiting the ISR delayed photoreceptor loss. Furthermore, supplementing asparagine, which is synthesized from aspartate, delayed photoreceptor degeneration. Hence, Gln catabolism is integral to photoreceptor health, and these data reveal a novel metabolic axis in these metabolically-demanding neurons.

Severe Spontaneous Tilt of Scleral-Fixated Intraocular Lenses.

PURPOSE: To report and evaluate a multicenter series of 18 cases of severe, spontaneous IOL tilt involving the flanged intrascleral haptic fixation technique (FISHF). DESIGN: Clinical study with historical controls. METHODS: We report a cross-sectional study of 46 FISHF cases using the CT Lucia 602 IOL at a single academic center over a period of 24 weeks to determine the incidence of severe rotisserie-style rotational tilt. These rates were then compared with the same time-frame the prior year to help determine if this is a new phenomenon. Additional cases of severe tilt were solicited from another 4 academic centers. RESULTS: Among 46 FISHF cases at a single center, 5 developed severe tilt. No clear pattern in surgical technique, ocular history, or ocular anatomy was evident in these cases compared with controls, although the involved IOLs clustered within a narrow diopter range, indicative of a batch effect. In the same 24-week interval the year before, 33 FISHF cases were performed, none of which exhibited severe rotational tilt. In our multicenter dataset, 18 cases of tilt were identified. Surgeons included fellow and early-career physicians as well as surgeons with multiple years of experience with the Yamane technique. A variety of surgical approaches for FISHF were represented. In at least 8 of the cases, haptic rotation and/or dehiscence at the optic-haptic junction were documented. CONCLUSIONS: The identification of haptic rotation and dehiscence intraoperatively in several cases may reflect a new stability issue involving the optic-haptic junction.

Increase in Retinal Detachment Repair Over a Ten-Year Period at an Academic Center Compared to National Trends.

BACKGROUND AND OBJECTIVE: This study aimed to determine whether cases of surgical retinal detachment (RD) repair at a tertiary care center from January 1, 2011 to December 31, 2020 increased proportionately to macular surgery cases as a control and to national trends. PATIENTS AND METHODS: Current Procedural Terminology codes were used to identify cases of primary RD repair (67107, 67108), complex RD repair (67113), pneumatic retinopexy (67110), and vitrectomy with membrane peeling (67041, 67042) at an academic center and in the Part B National Summary Data Files. Numbers of cases and mean case times at the academic center were determined. RESULTS: We identified 5,183 and 948,831 operative cases locally and nationally, respectively. Between 2011 and 2019, the total volume of RD repair at the academic center increased by 118.7%, compared to 23.3% for cases of membrane peeling. In contrast, surgical RD repairs and membrane peelings increased by 26.0% and 6.8% cases nationally. The ratio of RD repairs to membrane peelings from 2011 to 2019 increased from 1.5 to 2.6 locally compared to 0.6 to 0.7 nationally. Complex RD repairs increased more than primary RD repairs locally (129.3% vs 110.9% cases) and less than primary RD repairs nationally (20.6% versus 30.2% cases). CONCLUSION: Cases of surgical RD repair increased disproportionately compared to macular surgery at our institution and compared to RD repairs nationwide. [Ophthalmic Surg Lasers Imaging Retina 2023;54:505-511.].

Metabolic Alterations Caused by Simultaneous Loss of HK2 and PKM2 Leads to Photoreceptor Dysfunction and Degeneration.

HK2 and PKM2 are two main regulators of aerobic glycolysis. Photoreceptors (PRs) use aerobic glycolysis to produce the biomass necessary for the daily renewal of their outer segments. Previous work has shown that HK2 and PKM2 are important for the normal function and long-term survival of PRs but are dispensable for PR maturation, and their individual loss has opposing effects on PR survival during acute nutrient deprivation. We generated double conditional (dcKO) mice lacking HK2 and PKM2 expression in rod PRs. Western blotting, immunofluorescence, optical coherence tomography, and electroretinography were used to characterize the phenotype of dcKO animals. Targeted and stable isotope tracing metabolomics, qRT-PCR, and retinal oxygen consumption were performed. We show that dcKO animals displayed early shortening of PR inner/outer segments, followed by loss of PRs with aging, much more rapidly than either knockout alone without functional loss as measured by ERG. Significant alterations to central glucose metabolism were observed without any apparent changes to mitochondrial function, prior to PR degeneration. Finally, PR survival following experimental retinal detachment was unchanged in dcKO animals as compared to wild-type animals. These data suggest that HK2 and PKM2 have differing roles in promoting PR neuroprotection and identifying them has important implications for developing therapeutic options for combating PR loss during retinal disease.

Development of Novel Small-Molecule Activators of Pyruvate Kinase Muscle Isozyme 2, PKM2, to Reduce Photoreceptor Apoptosis.

Treatment options are lacking to prevent photoreceptor death and subsequent vision loss. Previously, we demonstrated that reprogramming metabolism via the pharmacologic activation of PKM2 is a novel photoreceptor neuroprotective strategy. However, the features of the tool compound used in those studies, ML-265, preclude its advancement as an intraocular, clinical candidate. This study sought to develop the next generation of small-molecule PKM2 activators, aimed specifically for delivery into the eye. Compounds were developed that replaced the thienopyrrolopyridazinone core of ML-265 and modified the aniline and methyl sulfoxide functional groups. Compound 2 demonstrated that structural changes to the ML-265 scaffold are tolerated from a potency and efficacy standpoint, allow for a similar binding mode to the target, and circumvent apoptosis in models of outer retinal stress. To overcome the low solubility and problematic functional groups of ML-265, compound 2's efficacious and versatile core structure for the incorporation of diverse functional groups was then utilized to develop novel PKM2 activators with improved solubility, lack of structural alerts, and retained potency. No other molecules are in the pharmaceutical pipeline for the metabolic reprogramming of photoreceptors. Thus, this study is the first to cultivate the next generation of novel, structurally diverse, small-molecule PKM2 activators for delivery into the eye.

Rod photoreceptor-specific deletion of cytosolic aspartate aminotransferase, GOT1, causes retinal degeneration.

Photoreceptor cell death is the cause of vision loss in many forms of retinal disease. Metabolic dysfunction within the outer retina has been shown to be an underlying factor contributing to photoreceptor loss. Therefore, a comprehensive understanding of the metabolic pathways essential to photoreceptor health and function is key to identifying novel neuroprotective strategies. Glutamic-oxaloacetic transaminase 1 (Got1) encodes for a cytosolic aspartate aminotransferase that reversibly catalyzes the transfer of an amino group between glutamate and aspartate and is an important aspect of the malate-aspartate shuttle (MAS), which transfers reducing equivalents from the cytosol to the mitochondrial matrix. Previous work has demonstrated that the activity of this enzyme is highest in photoreceptor inner segments. Furthermore, ex vivo studies have demonstrated that the retina relies on aspartate aminotransferase for amino acid metabolism. Importantly, aspartate aminotransferase has been suggested to be an early biomarker of retinal degeneration in retinitis pigmentosa and a possible target for neuroprotection. In the present study, we characterized the effect of Got1 deletion on photoreceptor metabolism, function, and survival in vivo by using a rod photoreceptor-specific, Got1 knockout mouse model. Loss of the GOT1 enzyme from rod photoreceptors resulted in age-related photoreceptor degeneration with an accumulation of retinal aspartate and NADH and alterations in the expression of genes involved in the MAS, the tricarboxylic acid (TCA) cycle, and redox balance. Hence, GOT1 is critical to in vivo photoreceptor metabolism, function, and survival.

A versatile pumpless multi-channel fluidics system for maintenance and real-time functional assessment of tissue and cells.

To address the needs of the life sciences community and the pharmaceutical industry in pre-clinical drug development to both maintain and continuously assess tissue metabolism and function with simple and rapid systems, we improved on the initial BaroFuse to develop it into a fully functional, pumpless, scalable multi-channel fluidics instrument that continuously measures changes in oxygen consumption and other endpoints in response to test compounds. We and several other laboratories assessed it with a wide range of tissue types including retina, pancreatic islets, liver, and hypothalamus with both aqueous and gaseous test compounds. The setup time was less than an hour for all collaborating groups, and there was close agreement between data obtained from the different laboratories. This easy-to-use system reliably generates real-time metabolic and functional data from tissue and cells in response to test compounds that will address a critical need in basic and applied research.

A Caveat About Financial Incentives for Anti-Vascular Endothelial Growth Factor Therapy for Diabetic Retinopathy.

PURPOSE: To highlight the financial incentive to the physician of choosing an intravitreal anti-vascular endothelial growth factor (VEGF)-based strategy for treating non-proliferative and proliferative diabetic retinopathy, and its possible risks to the patient and costs to the health care system. DESIGN: Perspective with retrospective cost and profit analysis. METHODS: Review and synthesis of selected literature on the treatment of diabetic retinopathy, with interpretation of activity-based and time-based costing of an intravitreal aflibercept strategy for diabetic retinopathy. Data from the DRCR Retina Network Protocols W and AB and PANORAMA trial were used to illustrate the potential financial incentive underlying such a treatment strategy. RESULTS: Physician treatment algorithms for diabetic vitreous hemorrhage and non-proliferative diabetic retinopathy may be influenced by the substantial financial incentives that intravitreal aflibercept strategies present, despite functional equivalence with alternative and less profitable strategies. For example, pursuing an intravitreal aflibercept-based strategy for diabetic vitreous hemorrhage presents a 76% increased profit over pars plana vitrectomy with laser, with equivalent functional outcomes. For non-proliferative diabetic retinopathy, preventative aflibercept injections represent a potential 414% increase in profit over observation and an increased cost of $12,164 to $17,542 over 2 years per patient, with no improvement in visual function. These findings demonstrate that there may be misaligned financial incentives in the management of diabetic retinopathy. CONCLUSIONS: While anti-VEGF therapy is a useful tool in the management of proliferative diabetic retinopathy and diabetic macular edema, it is believed that physicians should avoid overreliance on anti-VEGF injections in the treatment of diabetic retinopathy. Retinal specialists should be cognizant of the limitations, costs, and risks of anti-VEGF monotherapy and prophylactic therapy, and of the imperative to avoid bias towards financially remunerative practice patterns when equally effective alternatives exist.

Iatrogenic Paracentral Visual Field Defect After Pars Plana Vitrectomy for Macula-On Retinal Detachment Repair.

Perfluorocarbon liquid (PFCL) is an important adjunct in pars plana vitrectomy (PPV) for complex retinal detachment (RD). Complete removal of PFCL is critical to prevent retinal inflammation and cellular toxicity, but removal is not risk-free. We report a case of a new postoperative onset paracentral visual field defect after PPV with PFCL use for treatment of a macula-on RD. We present pre- and postoperative imaging that suggests a likely perioperative iatrogenic cause. [Ophthalmic Surg Lasers Imaging Retina 2022;53:644-646.].

Association of metformin and development of dry age-related macular degeneration in a U.S. insurance claims database.

PURPOSE: To assess whether metformin is associated with dry age-related macular degeneration (dAMD) development. METHODS: In this retrospective cohort study, patients enrolled in a nationwide U.S. medical insurance claims database from 2002 to 2016 were included if they had diabetes mellitus, were ⩾55 years old, and were enrolled for ⩾2 years without a prior AMD diagnosis. The primary exposure was metformin use analyzed as either active or prior use or cumulative metformin dosage over the study period. A time updating Cox proportional hazard regression was used to estimate the hazard ratio of dAMD incidence with metformin exposure. RESULTS: Among 1,007,226 diabetic enrollees, 53.3% were female and 66.4% were white with a mean hemoglobin A1c of 6.8%. Of eligible enrollees, 166,115 (16.5%) were taking metformin at the index date. Over the study period, 29,818 (3.0%) participants developed dAMD. In the active versus prior use of metformin model, active use conferred an increased hazard of developing dAMD (HR, 1.08; 95% CI, 1.04-1.12) while prior use had a decreased hazard (HR, 0.95; 95% CI 0.92-0.98). The cumulative metformin dosage model showed a significant trend toward increased hazard of dAMD incidence with increasing cumulative dosage (p < 0.001), with the lowest dosage quartile having decreased hazard of dAMD incidence (HR, 0.95; 95% CI, 0.91-0.99) and the highest having increased hazard (HR, 1.07; 95% CI, 1.01-1.13). CONCLUSIONS: Small, conflicting associations between metformin exposure and development of dAMD were observed depending on cumulative dosage and whether drug use was active, suggesting metformin did not substantially affect the development of dAMD.

SEROLOGY NEGATIVE BARTONELLA NEURORETINITIS IN AN IMMUNOCOMPROMISED PATIENT.

BACKGROUND/PURPOSE: To report a case of serology-negative severe disseminated Bartonella neuroretinitis in an immunocompromised patient in which diagnosis was made by detection of B. henselae DNA by universal polymerase chain reaction of brain tissue. METHODS: Case report. RESULTS: A 57-year-old man with immunoglobulin A vasculitis on immunosuppressive therapy presented with lethargy, weight loss, and bilateral decreased vision. Fundus examination revealed bilateral mild vitritis, marked optic disc edema, vascular sheathing, and numerous white inner retinal and preretinal lesions. Brain magnetic resonance imaging revealed multiple foci of restricted diffusion and a ring-enhancing focus in the left parietal lobe. Serologies, cerebrospinal fluid, and vitreous biopsies were all negative for Bartonella. A brain biopsy was performed and B. henselae DNA was detected by universal polymerase chain reaction of the specimen. The patient demonstrated resolution of fundus findings with antibiotic treatment. Repeat serological testing demonstrated seroconversion. CONCLUSION: In immunocompromised patients, infection by Bartonella henselae can present as severe disseminated disease. Establishing the diagnosis can be challenging as serologic testing is often unrevealing in the setting of a blunted immune response. Polymerase chain reaction has been used in select cases to establish the diagnosis.

Photoreceptor metabolic reprogramming: current understanding and therapeutic implications.

Acquired and inherited retinal disorders are responsible for vision loss in an increasing proportion of individuals worldwide. Photoreceptor (PR) death is central to the vision loss individuals experience in these various retinal diseases. Unfortunately, there is a lack of treatment options to prevent PR loss, so an urgent unmet need exists for therapies that improve PR survival and ultimately, vision. The retina is one of the most energy demanding tissues in the body, and this is driven in large part by the metabolic needs of PRs. Recent studies suggest that disruption of nutrient availability and regulation of cell metabolism may be a unifying mechanism in PR death. Understanding retinal cell metabolism and how it is altered in disease has been identified as a priority area of research. The focus of this review is on the recent advances in the understanding of PR metabolism and how it is critical to reduction-oxidation (redox) balance, the outer retinal metabolic ecosystem, and retinal disease. The importance of these metabolic processes is just beginning to be realized and unraveling the metabolic and redox pathways integral to PR health may identify novel targets for neuroprotective strategies that prevent blindness in the heterogenous group of retinal disorders.