Retinal artery occlusion in young patients without typical cardiovascular risk factors: etiologies, prognosis, and suggested work-up.

PURPOSE: To understand the etiology, work-up, and secondary systemic and ocular events of retinal artery occlusion (RAO) in young patients (≤ 45 years old) without typical cardiovascular risk factors. METHODS: Retrospective longitudinal case series of 18 young patients with RAO and without typical cardiovascular risk factors evaluated at the University of Michigan Medicine Health System between the year 2000 and 2022. Laboratory and imaging studies performed at the time of RAO diagnosis, along with systemic and ocular events during follow-up, were recorded. These data were combined with data from a literature review of 74 similar patients experiencing a RAO. RESULTS: Fifteen (83%) of patients were female and 10 (56%) suffered a branch retinal artery occlusion (BRAO). 56% of patients had one risk factor associated with cryptogenic stroke, most commonly a migraine history (33%). The most frequent etiology of RAO was vasculitis (28%), followed by idiopathic (22%) and patent foramen ovale (PFO, 17%). Three out of four patients with idiopathic RAOs developed new migraines around the time of RAO diagnosis, whereas none of the patients with a clear etiology had new onset migraines (n = 14). No patients suffered a stroke or myocardial infarction (MI) in the follow-up period (average 3.6 years ± 3.2 years). Two patients (11%) suffered a repeat RAO, both of whom were diagnosed with a vasculitis. Patients with isolated retinal vasculitis required repeat fluorescein angiograms for up to 2 years after the initial event to definitively identify the vasculitic etiology of the RAO. When our data are pooled with similarly healthy patients from previously published RAO series, structural/functional cardiac abnormalities and vasculitides are the most common identifiable etiologies for RAOs in this group. CONCLUSION: The most common identifiable etiologies of RAO in young patients with low cardiovascular risk are structural/functional cardiac abnormalities and vasculitides, with a small range of additional causes/associations accounting for remaining cases. We suggest a focused work-up algorithm to rapidly identify etiologies in this group while minimizing unnecessary testing. The long-term risk of systemic or ocular secondary events in these patients is low regardless of the etiology of their RAO.

Reassessing retinal pigment epithelial ketogenesis: Enzymatic assays for ketone body levels provide inaccurate results.

The retinal pigment epithelium (RPE) is omnivorous and can utilize a wide range of substrates for oxidative phosphorylation. Certain tissues with high mitochondrial metabolic load are capable of ketogenesis, a biochemical pathway that consolidates acetyl-CoA into ketone bodies. Earlier work demonstrated that the RPE expresses the rate-limiting enzyme for ketogenesis, 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), and that the RPE indeed produces ketone bodies, including beta-hydroxybutyrate (ß-HB). Prior work, based on detecting ß-HB via enzymatic assays, suggested that differentiated cultures of primary RPE preferentially export ß-HB across the apical membrane. Here, we compare the accuracy of measuring ß-HB by enzymatic assay kits to mass spectrometry analysis. We found that commercial kits lack the sensitivity to accurately measure the levels of ß-HB in RPE cultures and are prone to artifact. Using mass spectrometry, we found that while RPE cultures secrete ß-HB, they do so equally to both apical and basal sides. We also find RPE is capable of consuming ß-HB as levels rise. Using isotopically labeled glucose, amino acid, and fatty acid tracers, we found that carbons from both fatty acids and ketogenic amino acids, but not from glucose, produce ß-HB. Altogether, we substantiate ß-HB secretion in RPE but find that the secretion is equal apically and basally, RPE ß-HB can derive from ketogenic amino acids or fatty acids, and accurate ß-HB assessment requires mass spectrometric analysis.

Drug Approval for the Treatment of Geographic Atrophy: How We Got Here and Where We Need to Go.

PURPOSE: To discuss the clinical trial results leading to the US Food and Drug Administration (FDA) approval of anti-complement therapies for geographic atrophy (GA), perspectives on functional data from the GA clinical trials, and how lessons from the FDA approval may guide future directions for basic and clinical research in AMD. DESIGN: Selected literature review with analysis and perspective METHODS: We performed a targeted review of publicly available data from the clinical trials of pegcetacoplan and avacincaptad for the treatment of GA, as well as scientific literature on the natural history of GA and the genetics and basic science of complement in AMD. RESULTS: The approval of pegcetacoplan and avacincaptad was based on an anatomic endpoint of a reduction in the rate of GA expansion over time. However, functional data from 2 phase 3 clinical trials for each drug demonstrated no visual benefit to patients in the treatment groups. Review of the genetics of AMD and the basic science of the role for complement in AMD provides only modest support for targeting complement as treatment for GA expansion, and alternative molecular targets for GA treatment are therefore discussed. Reasons for the disconnect between anatomic and functional outcomes in the clinical trials of anti-complement therapies are discussed, providing insight to guide the configuration of future clinical studies for GA. CONCLUSION: Although avacincaptad and pegcetacoplan are our first FDA-approved treatments for GA, results from the clinical trials failed to show any functional improvement after 1 and 2 years, respectively, calling into question whether the drugs represent a "clinically relevant outcome." To improve the chances of more impactful therapies in the future, we provide basic-science rationale for pursuing non-complement targets; emphasize the importance of ongoing clinical research that more closely pins anatomic features of GA to functional outcomes; and provide suggestions for clinical endpoints for future clinical trials on GA.

Intraocular Pressure Lowering Associated With Worsening Optic Pit-Like Retinoschisis.

In this article, we present a case of optic pit-like macular retinoschisis in the absence of advanced glaucomatous cupping. Intraocular pressure (IOP)-lowering therapy, which was started due to an early concern for glaucoma, caused a worsening of the retinoschisis, which subsequently resolved on discontinuation of the IOP-lowering therapy. Lower IOP likely triggered intraretinal fluid accumulation by facilitating a translaminar gradient from the subarachnoid to intraretinal space. [Ophthalmic Surg Lasers Imaging Retina 2024;55:100-102.].

Medium Depth Influences O2 Availability and Metabolism in Human RPE Cultures.

Purpose: Retinal pigment epithelium (RPE) oxidative metabolism is critical for normal retinal function and is often studied in cell culture systems. Here, we show that conventional culture media volumes dramatically impact O2 availability, limiting oxidative metabolism. We suggest optimal conditions to ensure cultured RPE is in a normoxic environment permissive to oxidative metabolism. Methods: We altered the availability of O2 to human primary and induced pluripotent stem cell-derived RPE cultures directly via a hypoxia chamber or indirectly via the amount of medium over cells. We measured oxygen consumption rates (OCRs), glucose consumption, lactate production, 13C6-glucose and 13C5-glutamine flux, hypoxia inducible factor 1α (HIF-1α) stability, intracellular lipid droplets after a lipid challenge, transepithelial electrical resistance, cell morphology, and pigmentation. Results: Medium volumes commonly employed during RPE culture limit diffusion of O2 to cells, triggering hypoxia, activating HIF-1α, limiting OCR, and dramatically altering cell metabolism, with only minor effects on typical markers of RPE health. Media volume effects on O2 availability decrease acetyl-CoA utilization, increase glycolysis and reductive carboxylation, and alter the size and number of intracellular lipid droplets under lipid-rich conditions. Conclusions: Despite having little impact on visible and typical markers of RPE culture health, media volume dramatically affects RPE physiology "under the hood." As RPE-centric diseases like age-related macular degeneration involve oxidative metabolism, RPE cultures need to be optimized to study such diseases. We provide guidelines for optimal RPE culture volumes that balance ample nutrient availability from larger media volumes with adequate O2 availability seen with smaller media volumes.

Acetyl-CoA carboxylase Inhibition increases RPE cell fatty acid oxidation and limits apolipoprotein efflux.

Purpose: In age-related macular degeneration (AMD) and Sorsby's fundus dystrophy (SFD), lipid-rich deposits known as drusen accumulate under the retinal pigment epithelium (RPE). Drusen may contribute to photoreceptor and RPE degeneration in AMD and SFD. We hypothesize that stimulating ß-oxidation in RPE will reduce drusen accumulation. Inhibitors of acetyl-CoA carboxylase (ACC) stimulate ß-oxidation and diminish lipid accumulation in fatty liver disease. In this report we test the hypothesis that an ACC inhibitor, Firsocostat, limits the accumulation of lipid deposits in cultured RPE cells. Methods: We probed metabolism and cellular function in mouse RPE-choroid, human fetal- derived RPE cells, and induced pluripotent stem cell-derived RPE cells. We used 13 C6-glucose and 13 C16-palmitate to determine the effects of Firsocostat on glycolytic, Krebs cycle, and fatty acid metabolism. 13 C labeling of metabolites in these pathways were analyzed using gas chromatography-linked mass spectrometry. We quantified ApoE and VEGF release using enzyme-linked immunosorbent assays. Immunostaining of sectioned RPE was used to visualize ApoE deposits. RPE function was assessed by measuring the trans-epithelial electrical resistance (TEER). Results: ACC inhibition with Firsocostat increases fatty acid oxidation and remodels lipid composition, glycolytic metabolism, lipoprotein release, and enhances TEER. When human serum is used to induce sub-RPE lipoprotein accumulation, fewer lipoproteins accumulate with Firsocostat. In a culture model of Sorsby's fundus dystrophy, Firsocostat also stimulates fatty acid oxidation, improves morphology, and increases TEER. Conclusions: Firsocostat remodels intracellular metabolism and improves RPE resilience to serum-induced lipid deposition. This effect of ACC inhibition suggests that it could be an effective strategy for diminishing drusen accumulation in the eyes of patients with AMD.

Improved Lipofuscin Models and Quantification of Outer Segment Phagocytosis Capacity in Highly Polarized Human Retinal Pigment Epithelial Cultures.

The daily phagocytosis of photoreceptor outer segments by the retinal pigment epithelium (RPE) contributes to the accumulation of an intracellular aging pigment termed lipofuscin. The toxicity of lipofuscin is well established in Stargardt's disease, the most common inherited retinal degeneration, but is more controversial in age-related macular degeneration (AMD), the leading cause of irreversible blindness in the developed world. Determining lipofuscin toxicity in humans has been difficult, and animal models of Stargardt's have limited toxicity. Thus, in vitro models that mimic human RPE in vivo are needed to better understand lipofuscin generation, clearance, and toxicity. The majority of cell culture lipofuscin models to date have been in cell lines or have involved feeding RPE a single component of the complex lipofuscin mixture rather than fragments/tips of the entire photoreceptor outer segment, which generates a more complete and physiologic lipofuscin model. Described here is a method to induce the accumulation of lipofuscin-like material (termed undigestible autofluorescence material, or UAM) in highly differentiated primary human pre-natal RPE (hfRPE) and induced pluripotent stem cell (iPSC) derived RPE. UAM accumulated in cultures by repeated feedings of ultraviolet light-treated OS fragments taken up by the RPE via phagocytosis. The key ways that UAM approximates and differs from lipofuscin in vivo are also discussed. Accompanying this model of lipofuscin-like accumulation, imaging methods to distinguish the broad autofluorescence spectrum of UAM granules from concurrent antibody staining are introduced. Finally, to assess the impact of UAM on RPE phagocytosis capacity, a new method for quantifying outer segment fragment/tips uptake and breakdown has been introduced. Termed "Total Consumptive Capacity", this method overcomes potential misinterpretations of RPE phagocytosis capacity inherent in classic outer segment "pulse-chase" assays. The models and techniques introduced here can be used to study lipofuscin generation and clearance pathways and putative toxicity.

Specific Deoxyceramide Species Correlate with Expression of Macular Telangiectasia Type 2 (MacTel2) in a SPTLC2 Carrier HSAN1 Family.

Hereditary sensory and autonomic neuropathy type 1 (HSAN1/HSN1) is a peripheral neuropathy most commonly associated with pathogenic variants in the serine palmitoyltransferase complex (SPTLC1, SPTLC2) genes, which are responsible for sphingolipid biosynthesis. Recent reports have shown that some HSAN1 patients also develop macular telangiectasia type 2 (MacTel2), a retinal neurodegeneration with an enigmatic pathogenesis and complex heritability. Here, we report a novel association of a SPTLC2 c.529A>G p.(Asn177Asp) variant with MacTel2 in a single member of a family that otherwise has multiple members afflicted with HSAN1. We provide correlative data to suggest that the variable penetrance of the HSAN1/MacTel2-overlap phenotype in the proband may be explained by levels of certain deoxyceramide species, which are aberrant intermediates of sphingolipid metabolism. We provide detailed retinal imaging of the proband and his HSAN1+/MacTel2- brothers and suggest mechanisms by which deoxyceramide levels may induce retinal degeneration. This is the first report of HSAN1 vs. HSAN1/MacTel2 overlap patients to comprehensively profile sphingolipid intermediates. The biochemical data here may help shed light on the pathoetiology and molecular mechanisms of MacTel2.

A Telephone Triage System for Patients Calling with Symptoms of a Posterior Vitreous Detachment.

PURPOSE: The purpose of the study was to develop a simple telephone questionnaire, without physical examination input, that predicts which patients calling with symptoms of a posterior vitreous detachment (PVD) have a retinal tear (RT) or rhegmatogenous retinal detachment (RD). DESIGN: Prospective cohort (quality improvement) study. PARTICIPANTS: All patients with symptoms consistent with a PVD calling a major academic ophthalmology department over a 4-month period in 2020 and who were seen on follow-up within 1.5 months (211 screened and 193 included). METHODS: A comprehensive telephone questionnaire assessing for RT/RD risk factors was administered by telephone triage staff to all patients calling with symptoms of flashes, floaters, or curtain/veil in their vision. Multivariable logistic regression was used to determine risk factors most predictive of having an RT/RD during the add-on visit. Risk factor odds ratios were used to develop an RT/RD risk score. MAIN OUTCOMES MEASURES: Development of a clinical risk score for having an RT/RD at the add-on visit after telephone triage. RESULTS: Approximately 55% of patients were previously established in the retina clinic, 26% were new to the department, 19% were previously established in the comprehensive clinic, and 7% had an RT/RD at the add-on visit. Out of 23 questions and 70 prespecified possible answers from the telephone questionnaire, the final clinical risk score for RT/RDs was derived from 7 questions and 15 possible answers. The simplified questionnaire can be administered quickly by telephone operators without any reference to physical examination or the patient's chart. The receive-operator curve for our final multivariable logistic regression and clinical risk score models have an area under the curve of > 0.90. Using a conservative clinical risk score, approximately 50% of all patients without an RT/RD can be safely seen nonurgently. Progressively higher scores can be used to determine relative urgency of an appointment. CONCLUSIONS: To our knowledge, this is the first study to predict risk of an RT/RD in a patient calling with symptoms consistent with a PVD without reference to the patient's physical examination or chart. Our clinical risk scoring system can be used to determine urgency of an add-on appointment and increase the number of low-risk patients with symptomatic PVDs who are scheduled routinely. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Concentric Macular Rings Without Ocular Pathology.

Concentric macular rings (CMRs) of Henle's fiber layer (HFL) are an uncommon imaging phenomenon previously associated with foveal hypoplasia and epiretinal membrane. Here, we present a case of a 15-year-old boy with bilateral CMRs, normal visual function, and no ocular pathology. These bilateral findings in the absence of vitreomacular traction, foveal hypoplasia, or any other ocular abnormality suggest that macular rings may occur as a normal but rare variant of HFL architecture. [Ophthalmic Surg Lasers Imaging Retina. 2021;52:353-355.].

The Diagnostic Conundrum of Retinitis and a Pigmented Scar.

We report a finding of a pigmented chorioretinal scar with acute retinal necrosis (ARN) caused by herpes simplex virus 2 (HSV-2) infection rather than toxoplasma, creating an initial diagnostic dilemma. A 53-year-old functionally monocular male presented with painless floaters and blurry vision in his seeing eye over a period of 4 days. An exam demonstrated anterior chamber (AC) reaction, vitritis, multifocal patches of whitening, and an occlusive retinal vasculitis. A superior pigmented chorioretinal scar with overlying contracted vitreous was noted in the periphery with no adjacent retinal whitening. The patient was treated for both ARN and toxoplasma chorioretinitis until PCR study of the vitreous and AC returned positive for HSV-2 and negative for toxoplasmosis. Management consisted of a dual therapy regimen of both oral and intravitreal antiviral agents as well as oral corticosteroids. The patient's clinical course was complicated by rhegmatogenous retinal detachment within 2 weeks after symptom onset, requiring pars plana vitrectomy with silicone oil and intraoperative intraocular incubation with foscarnet. We review emerging evidence for pigmented chorioretinal scars in ARN specifically caused by HSV-2, as well as diagnostic and treatment dilemmas in the management of ARN and ARN detachments.

Pharmacologic activation of autophagy without direct mTOR inhibition as a therapeutic strategy for treating dry macular degeneration.

Dry age-related macular degeneration (AMD) is marked by the accumulation of extracellular and intracellular lipid-rich deposits within and around the retinal pigment epithelium (RPE). Inducing autophagy, a conserved, intracellular degradative pathway, is a potential treatment strategy to prevent disease by clearing these deposits. However, mTOR inhibition, the major mechanism for inducing autophagy, disrupts core RPE functions. Here, we screened autophagy inducers that do not directly inhibit mTOR for their potential as an AMD therapeutic in primary human RPE culture. Only two out of more than thirty autophagy inducers tested reliably increased autophagy flux in RPE, emphasizing that autophagy induction mechanistically differs across distinct tissues. In contrast to mTOR inhibitors, these compounds preserved RPE health, and one inducer, the FDA-approved compound flubendazole (FLBZ), reduced the secretion of apolipoprotein that contributes to extracellular deposits termed drusen. Simultaneously, FLBZ increased production of the lipid-degradation product ß-hydroxybutyrate, which is used by photoreceptor cells as an energy source. FLBZ also reduced the accumulation of intracellular deposits, termed lipofuscin, and alleviated lipofuscin-induced cellular senescence and tight-junction disruption. FLBZ triggered compaction of lipofuscin-like granules into a potentially less toxic form. Thus, induction of RPE autophagy without direct mTOR inhibition is a promising therapeutic approach for dry AMD.

A novel OCT signature in leukemic papillopathy masquerading as autoimmune or infectious uveitis.

PURPOSE: With therapeutic advances, central nervous system (CNS) involvement in leukemia has become more common. Leukemic optic disc infiltration, often a clinical diagnosis, can present as an isolated finding in primary or relapsed CNS disease and therefore requires early recognition. Not previously well appreciated, we report here signs of intraocular inflammation accompanying leukemic optic disc infiltration, suggesting infectious or non-infectious uveitis as an alternative diagnosis. We describe a novel optical coherence tomography (OCT) sign favoring leukemic infiltration. METHODS: Retrospective consecutive case series of all leukemic patients with disc edema (5 patients, 6 eyes) presenting to the University of Michigan's Ocular Oncology Clinic between October 2019 and March 2020. RESULTS: We report five leukemic patients (6 eyes) who were evaluated for disc edema and vitritis and eventually diagnosed with leukemic papillopathy. All five patients initially had a bland lumbar puncture (LP), and all four patients who underwent magnetic resonance imaging (MRI) had no retrobulbar nerve involvement. Clinical findings included preserved visual acuity (n = 5 eyes, 83%), anterior chamber (AC) cell (n = 3 eyes, 50%), vitreous cell (n = 6 eyes, 100%), and retinal whitening (n = 4 eyes, 66%). In five eyes (83%), a diagnosis of infectious or non-infectious uveitis was initially considered. The OCT finding of inner retinal thickening and loss of inner retinal lamination with largely preserved outer retinal architecture helped point towards a leukemic infiltrative process emanating from the disc and spreading retrograde through the nerve fiber layer. CONCLUSIONS: These cases highlight the difficulty of distinguishing intraocular inflammation associated with leukemic papillopathy from infectious or non-infectious uveitis, especially considering bland LP and negative retrobulbar MRI signal in all our patients. We propose juxtapapillary inner retinal infiltration with the loss of inner retinal lamination and relative preservation of outer retinal architecture on OCT imaging as a finding that supports the diagnosis of leukemic papillopathy.

Multiple sclerosis presenting as acute acquired comitant esotropia in a pediatric patient.

Acute acquired comitant esotropia (AACE) is a rare form of esotropia in the older pediatric population. Although the workup for pediatric AACE varies, patients often do not undergo lab testing and imaging, because the overwhelming majority of cases are idiopathic. We describe AACE as the presenting manifestation of multiple sclerosis in a pediatric patient. His only other finding was a horizontal jerk nystagmus isolated to end gaze. Magnetic resonance imaging revealed extensive demyelinating lesions, with a small thalamic lesion possibly accounting for his esotropia. Our case underscores the need for extensive diagnostic workup for any ophthalmic or neurologic findings or symptoms accompanying AACE.

On-Call Examinations for Acute Onset of Flashes, Floaters, or Curtain by Junior Ophthalmology Residents: Outcomes, Safety, and Resource Use.

PURPOSE: To determine whether an on-call system serviced by junior residents can safely triage patients with symptoms concerning for posterior vitreous detachment, retinal tear, and retinal detachment. DESIGN: Quality improvement study structured as a prospective cohort study. PARTICIPANTS: All symptomatic patients seen in 2017 by an on-call junior resident were followed up (257 patients). Those with follow-up within 6 months of initial presentation (228 patients, 246 unique encounters) were included. METHODS: We prospectively tracked all symptomatic patients seen on-call by a junior resident in 2017 at a major academic medical center. MAIN OUTCOME MEASURES: Incidence and predictors of true retinal tears or detachments, false-positive tears or detachments, false-negative tears or detachments, and resource use. RESULTS: Of 246 symptomatic encounters, 83 (33.7%) had a perceived retinal tear or detachment. Residents used B-scan ultrasonography in a high number of encounters (41.0%). Ten (4.1%) false-positive tears or detachments were identified, with the presence of intraretinal hemmorhage predicting a false-positive examination (adjusted odds ratio, 3.86; 95% confidence interval, 1.1-13.5). Thirteen (5.3%) false-negative tears and no false-negative detachments were identified. Eleven (84.6%) false-negative tears underwent follow-up within days based on high-risk characteristics, and no false-negative tears progressed to detachment at follow-up. Measures of resource use included an in-person confirmation of examination findings by the senior resident or fellow in 59 encounters (24.0%) and shorter follow-up times to a retina rather than a nonretina clinic for 52 of 151 patients who showed no pathologic features on initial examination. CONCLUSIONS: Junior residents can safely provide on-call triage of patients with symptoms concerning for a posterior vitreous detachment, retinal tear, or retinal detachment. The system requires moderate resource use, including occasional confirmatory examinations by a second physician and shorter follow-up times to retina clinic for high-risk patients.