September 2022

Xu C, Prager AJ, Alonso CD, Pawar AS. Insights From the Eye for Patients With Kidney Transplant. Transplant Proc 2022;Abstract
The eye and the kidney share structural and developmental similarities on a cellular and clinical level, and they are often affected by the same disease processes. Performing an eye exam to look for signs of conditions such as hypertension and diabetes can provide a helpful window into the health of the kidney. Patients with kidney transplants (KT) are a unique population that require close monitoring. These patients are maintained on a number of immunosuppressive medications and may face complications such as medication side effects, infections, and graft rejection. Patients with KT are at higher risk of both infectious and noninfectious eye conditions related to underlying systemic disease or use of immunosuppressive medications. Screening for eye conditions is important because preserving visual function is integral to quality of life, and also because the eye exam can help with early detection and treatment of systemic conditions. Here we describe some of the common eye findings and conditions in patients with KT. We recommend that patients with KT receive annual eye exams, and we hope that the information provided here can help nephrologists become more familiar with eye findings and identify situations where a referral to ophthalmology is warranted.
Oke I, Heidary G, Mantagos IS, Shah AS, Hunter DG. A decline in the strabismus surgical experience of ophthalmology residents in the United States from 2010 to 2019. J AAPOS 2022;Abstract
Subspecialty exposure during residency can influence the future pursuit of fellowship training. In this study, we compared the trends in strabismus surgical experience reported by graduating ophthalmology residents in the United States with other categories of ophthalmic surgery. Over the 10-year period (2010-2019), there was a decline in the total number of strabismus procedures performed during residency by ophthalmology residents graduating in a given year (1.4 fewer cases per year; 95% CI, 1.1-1.6 [P < 0.001]). Although several surgical categories experienced a decrease in cases performed in the assistant role, strabismus surgery was the only category with a decrease in cases performed in the surgeon role (0.4 fewer cases per year; 95% CI, 0.3-0.5 [P < 0.001]).
Valdes L, Cox JT, Yang J, Susarla G, Han S, Papaliodis GN, Sobrin L. Anti-infliximab antibodies and clinical response in noninfectious uveitis and scleritis patients treated with infliximab: A retrospective review. Am J Ophthalmol Case Rep 2022;27:101634.Abstract
Purpose: To investigate the clinical response to infliximab in ocular inflammation patients who develop anti-infliximab antibodies (AIA) vs. those patients who do not develop AIA. Observations: A retrospective review was performed of patients treated with infliximab for noninfectious uveitis (NIU) or scleritis. Clinical response was determined as a composite clinical endpoint and classified as complete, partial, or absent. Nine of 32 infliximab-treated patients (28%) were found to develop AIA. Among the AIA-positive patients, clinical response was complete in 7 patients (78%) and partial in 2 patients (22%). Among the AIA-negative patients, clinical response was complete in 15 patients (65%), partial in 6 patients (26%) and absent in 2 patients (9%). Serum infliximab levels tended to decrease with appearance of AIA but rarely became undetectable. Conclusions and Importance: In this pilot study, AIA-positive patients did not have diminished clinical response to infliximab when compared with AIA-negative patients. There was a high rate of complete clinical response to infliximab in this group of NIU and scleritis patients. Approximately a quarter of patients developed AIA. AIA-positive patients did not have diminished rates of clinical response when compared with AIA-negative patients. This suggests that routine AIA monitoring may not be clinically useful, although validation of this finding in larger cohorts is necessary.
Hoogsteen KMP, Szpiro S, Kreiman G, Peli E. Beyond the Cane: Describing Urban Scenes to Blind People for Mobility Tasks. ACM Trans Access Comput 2022;15(3)Abstract
Blind people face difficulties with independent mobility, impacting employment prospects, social inclusion, and quality of life. Given the advancements in computer vision, with more efficient and effective automated information extraction from visual scenes, it is important to determine what information is worth conveying to blind travelers, especially since people have a limited capacity to receive and process sensory information. We aimed to investigate which objects in a street scene are useful to describe and how those objects should be described. Thirteen cane-using participants, five of whom were early blind, took part in two urban walking experiments. In the first experiment, participants were asked to voice their information needs in the form of questions to the experimenter. In the second experiment, participants were asked to score scene descriptions and navigation instructions, provided by the experimenter, in terms of their usefulness. The descriptions included a variety of objects with various annotations per object. Additionally, we asked participants to rank order the objects and the different descriptions per object in terms of priority and explain why the provided information is or is not useful to them. The results reveal differences between early and late blind participants. Late blind participants requested information more frequently and prioritized information about objects' locations. Our results illustrate how different factors, such as the level of detail, relative position, and what type of information is provided when describing an object, affected the usefulness of scene descriptions. Participants explained how they (indirectly) used information, but they were frequently unable to explain their ratings. The results distinguish between various types of travel information, underscore the importance of featuring these types at multiple levels of abstraction, and highlight gaps in current understanding of travel information needs. Elucidating the information needs of blind travelers is critical for the development of more useful assistive technologies.
Yang M, Fjærvoll HK, Fjærvoll KA, Wang NH, Utheim TP, Serhan CN, Dartt DA. Sex-based differences in conjunctival goblet cell responses to pro-inflammatory and pro-resolving mediators. Sci Rep 2022;12(1):16305.Abstract
Many conjunctival inflammatory diseases differ between the sexes and altered conjunctival goblet cells (CGCs) response is often involved. Inflammation is initiated by the release of pro-inflammatory mediators and terminated by the biosynthesis of specialized pro-resolution mediators (SPMs). Herein, we determined the sex-based difference in the responses of CGCs to inflammatory stimuli or pro-resolving lipid SPMs and their interaction with sex hormones. GCs were cultured from pieces of human conjunctiva in RPMI media. CGCs were transferred 24 h before the start of experiments to phenol red-free and FBS-free media to minimize exogenous hormones. RT-PCR, immunofluorescence microscopy (IF), and Western Blot (WB) were performed to determine the presence of sex hormone receptors. Cellular response to pro-inflammatory stimuli or SPMs was studied by measuring the increase in intracellular [Ca2+] ([Ca2+]i) using fura 2/AM microscopy. Use of RT-PCR demonstrated estrogen receptor (ER) α in 4/5 males and 3/3 females; ERβ in 2/4 males and 2/3 females; and androgen receptors (AR) in 3/3 male and 3/3 female CGCs. Positive immunoreactivity by IF and protein expression by WB was detected using antibodies for the ERα and ERβ in 3/3 males and 3/3 females, while AR were only present in males. Significantly different Ca2+ responses between sexes were found with carbachol only at 10-3 M, but not with histamine or leukotriene (LT) B4 at any concentration used. Incubation with dihydrotestosterone (DHT), estrone (E1), or estradiol (E2) at 10-7 M for 30 min significantly inhibited the LTB4-stimulated [Ca2+]i increase in male and female CGCs. Incubation with DHT, E1, and E2 overnight significantly inhibited the LTB4 response in females, while DHT and E2 significantly inhibited the LTB4 response in males. The SPM lipoxin A4 (LXA4) (10-9-10-8 M), but not the resolvins D1 or D2, induced an [Ca2+]i increase that was significantly higher in males compared to females. We conclude that male and female CGCs showed differences in the expression of sex hormone receptors. Treatment with sex hormones altered pro-inflammatory mediator LTB4-induced response. Males compared to females have a higher response to the ω-6-fatty acid derived SPM LXA4, indicating males may terminate inflammation in conjunctival goblet cells faster than females.
Madjedi KM, Stuart KV, Chua SYL, Luben RN, Warwick A, Pasquale LR, Kang JH, Wiggs JL, Lentjes MA, Aschard H, Sattar N, Foster PJ, Khawaja AP, for and the and Consortium MRFGCUKBEV. The Association between Serum Lipids and Intraocular Pressure in 2 Large United Kingdom Cohorts. Ophthalmology 2022;129(9):986-996.Abstract
PURPOSE: Serum lipids are modifiable, routinely collected blood test features associated with cardiovascular health. We examined the association of commonly collected serum lipid measures (total cholesterol [TC], high-density lipoprotein cholesterol [HDL-C], low-density lipoprotein cholesterol [LDL-C], and triglycerides) with intraocular pressure (IOP). DESIGN: Cross-sectional study in the UK Biobank and European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk cohorts. PARTICIPANTS: We included 94 323 participants from the UK Biobank (mean age, 57 years) and 6230 participants from the EPIC-Norfolk (mean age, 68 years) cohorts with data on TC, HDL-C, LDL-C, and triglycerides collected between 2006 and 2009. METHODS: Multivariate linear regression adjusting for demographic, lifestyle, anthropometric, medical, and ophthalmic covariables was used to examine the associations of serum lipids with corneal-compensated IOP (IOPcc). MAIN OUTCOME MEASURES: Corneal-compensated IOP. RESULTS: Higher levels of TC, HDL-C, and LDL-C were associated independently with higher IOPcc in both cohorts after adjustment for key demographic, medical, and lifestyle factors. For each 1-standard deviation increase in TC, HDL-C, and LDL-C, IOPcc was higher by 0.09 mmHg (95% confidence interval [CI], 0.06-0.11 mmHg; P < 0.001), 0.11 mmHg (95% CI, 0.08-0.13 mmHg; P < 0.001), and 0.07 mmHg (95% CI, 0.05-0.09 mmHg; P < 0.001), respectively, in the UK Biobank cohort. In the EPIC-Norfolk cohort, each 1-standard deviation increase in TC, HDL-C, and LDL-C was associated with a higher IOPcc by 0.19 mmHg (95% CI, 0.07-0.31 mmHg; P = 0.001), 0.14 mmHg (95% CI, 0.03-0.25 mmHg; P = 0.016), and 0.17 mmHg (95% CI, 0.06-0.29 mmHg; P = 0.003). An inverse association between triglyceride levels and IOP in the UK Biobank (-0.05 mmHg; 95% CI, -0.08 to -0.03; P < 0.001) was not replicated in the EPIC-Norfolk cohort (P = 0.30). CONCLUSIONS: Our findings suggest that serum TC, HDL-C, and LDL-C are associated positively with IOP in 2 United Kingdom cohorts and that triglyceride levels may be associated negatively. Future research is required to assess whether these associations are causal in nature.
Agarwal A, Singh RB, Erckens RJ, Berendschot TTJM, Webers CAB. Quantitative Analysis of the Choroidal Vascularity in Eyes with Uveitis Using Optical Coherence Tomography Angiography: A Systematic Review. Ocul Immunol Inflamm 2022;:1-12.Abstract
PURPOSE: The purpose of this systematic review is to identify techniques used for quantification of choriocapillaris (CC) flow in eyes with uveitis using optical coherence tomography angiography (OCTA), report reliability and level of correlation with techniques such as indocyanine green angiography (ICGA). METHODS: A systematic search of several databases was done. The studies were analyzed for techniques of measurement, reliability, and correlation with other modalities. Risk of bias assessment was performed. RESULTS: Thirteen studies were included. CC vessel density (7 studies) and flow deficit area (4 studies) were the most used indices. There was significant heterogeneity in the studies due to differences in the scan protocol, thresholding strategy, and analysis. Comparison with ICGA was performed by only one study, and reliability indices were reported by only two studies. CONCLUSION: OCTA is a useful tool to measure the CC vascularity in eyes with uveitis. However, standardized acquisition and analysis protocols are needed.
Henao-Restrepo J, López-Murillo C, Valderrama-Carmona P, Orozco-Santa N, Gomez J, Gutiérrez-Vargas J, Moraga R, Toledo J, Littau JL, Härtel S, Arboleda-Velásquez JF, Sepulveda-Falla D, Lopera F, Cardona-Gómez GP, Villegas A, Posada-Duque R. Gliovascular alterations in sporadic and familial Alzheimer's disease: APOE3 Christchurch homozygote glioprotection. Brain Pathol 2022;:e13119.Abstract
In response to brain insults, astrocytes become reactive, promoting protection and tissue repair. However, astroglial reactivity is typical of brain pathologies, including Alzheimer's disease (AD). Considering the heterogeneity of the reactive response, the role of astrocytes in the course of different forms of AD has been underestimated. Colombia has the largest human group known to have familial AD (FAD). This group carries the autosomal dominant and fully penetrant mutation E280A in PSEN1, which causes early-onset AD. Recently, our group identified an E280A carrier who did not develop FAD. The individual was homozygous for the Christchurch mutation R136S in APOE3 (APOEch). Remarkably, APOE is the main genetic risk factor for developing sporadic AD (SAD) and most of cerebral ApoE is produced by astroglia. Here, we characterized astrocyte properties related to reactivity, glutamate homeostasis, and structural integrity of the gliovascular unit (GVU), as factors that could underlie the pathogenesis or protection of AD. Specifically, through histological and 3D microscopy analyses of postmortem samples, we briefly describe the histopathology and cytoarchitecture of the frontal cortex of SAD, FAD, and APOEch, and demonstrate that, while astrodegeneration and vascular deterioration are prominent in SAD, FAD is characterized by hyperreactive-like glia, and APOEch displays the mildest astrocytic and vascular alterations despite having the highest burden of Aβ. Notably, astroglial, gliovascular, and vascular disturbances, as well as brain cell death, correlate with the specific astrocytic phenotypes identified in each condition. This study provides new insights into the potential relevance of the gliovasculature in the development and protection of AD. To our knowledge, this is the first study assessing the components of the GVU in human samples of SAD, FAD, and APOEch.
Ho TC, Maamari RN, Kossler AL, Sears CM, Freitag SK, Reshef ER, Shinder R, Rootman DB, Diniz SB, Kahana A, Schlachter D, Do TH, Kally P, Turner S, Mokhtarzadeh A, Harrison AR, Hwang CJ, Kim HJ, Avila SA, Thomas DA, Magazin M, Wester ST, Lee WW, Clauss KD, Holds JB, Sniegowski M, Compton CJ, Briggs C, Malik AI, Lucarelli MJ, Burkat CN, Patel LG, Couch SM. Outcomes of Patients With Thyroid Eye Disease Partially Treated With Teprotumumab. Ophthalmic Plast Reconstr Surg 2022;Abstract
PURPOSE: In response to the coronavirus (COVID-19) pandemic, teprotumumab production was temporarily halted with resources diverted toward vaccine production. Many patients who initiated treatment with teprotumumab for thyroid eye disease were forced to deviate from the standard protocol. This study investigates the response of teprotumumab when patients receive fewer than the standard 8-dose regimen. METHODS: This observational cross-sectional cohort study included patients from 15 institutions with active or minimal to no clinical activity thyroid eye disease treated with the standard teprotumumab infusion protocol. Patients were included if they had completed at least 1 teprotumumab infusion and had not yet completed all 8 planned infusions. Data were collected before teprotumumab initiation, within 3 weeks of last dose before interruption, and at the visit before teprotumumab reinitiation. The primary outcome measure was reduction in proptosis more than 2 mm. Secondary outcome measures included change in clinical activity score (CAS), extraocular motility restriction, margin reflex distance-1 (MRD1), and reported adverse events. RESULTS: The study included 74 patients. Mean age was 57.8 years, and 77% were female. There were 62 active and 12 minimal to no clinical activity patients. Patients completed an average of 4.2 teprotumumab infusions before interruption. A significant mean reduction in proptosis (-2.9 mm in active and -2.8 mm in minimal to no clinical activity patients, P < 0.01) was noted and maintained during interruption. For active patients, a 3.4-point reduction in CAS (P < 0.01) and reduction in ocular motility restriction (P < 0.01) were maintained during interruption. CONCLUSIONS: Patients partially treated with teprotumumab achieve significant reduction in proptosis, CAS, and extraocular muscle restriction and maintain these improvements through the period of interruption.
Neerukonda VK, Lefebvre D, Chatson GP, Stagner AM. Silicone Granulomas of the Eyelids-A Case Series Illustrating a Distant Migratory Phenomenon. Ophthalmic Plast Reconstr Surg 2022;Abstract
PURPOSE: Exogenous silicone has been reported to migrate to anatomic sights far from an initial injection or implantation site; this phenomenon has been rarely described in the ocular adnexa, especially in the eyelids. We document 3 additional cases of distant migration of silicone implanted elsewhere in the body to the eyelids and review the prior literature on this uncommon event. METHODS: A retrospective chart review of 3 patients was conducted along with analysis of diagnostic histopathology. A comprehensive review of the literature regarding dissemination or migration of silicone to the eyelids in patients with either silicone breast implants or silicone facial filler use was performed. RESULTS: Cases of silicone migrating to the eyelids from silicone breast implants and silicone-based facial filler are outlined in Tables 1 and 2, respectively. There are 4 total reports of women with silicone breast implants, including the 2 described here, with evidence of migration of silicone to the eyelid. Similarly, 5 cases of silicone-based facial filler with resultant migration of filler to the eyelids were identified, including 2 of the cases presented in this report (1 patient had both silicone breast implants and silicone facial filler). CONCLUSION: Silicone is chemically inert, but is known to travel throughout the body, causing a resultant foreign body response in tissue that can adversely affect even the eyelids. Silicone has a relatively characteristic histologic appearance and diagnosis of silicone granuloma highlights the importance of obtaining a thorough clinical history, particularly regarding prior cosmetic injections or breast enhancement surgery. Foreign material/foreign body granuloma is important to consider in patients with deep eyelid nodules of unclear etiology.
Maleki A, Fernandez CC, Philip AM, Manhapra A, Chang PY, Foster SC. Acute macular neuroretinopathy in a patient with birdshot chorioretinopathy after intravitreal triamcinolone suspension injection. Eur J Ophthalmol 2022;:11206721221124653.Abstract
PURPOSE: To report a case of acute macular neuroretinopathy (AMN) after intravitreal triamcinolone acetonide (TRIESENCE®) injection for cystoid macular edema secondary to birdshot chorioretinopathy. METHOD: A case report. PATIENT: A 62-year-old female. RESULTS: The patient presented with acutely decreased vision and a ring scotoma around her central vision three days after intravitreal triamcinolone acetonide (TRIESENCE®) injection for cystoid macular edema in her right eye (OD) secondary to birdshot chorioretinopathy. She had undergone pars plana vitrectomy, cataract extraction, and secondary intraocular lens implantation OD three months prior to the recent injection. Best-corrected visual acuity (BCVA) was 20/1000 OD and 20/50 OS. Intraocular pressure was 21 mmHg OD and 12 mmHg OS. Fluorescein angiography demonstrated a hypofluorescent area in the perifoveal zone OD. Optical coherence tomography OD depicted hyperreflective areas in the outer nuclear layer, outer plexiform layer, and retinal pigment epithelium. We diagnosed her with AMN OD and started her on brimonidine three times a day OD. She came back a week later with resolved scotoma and her vision improved to 20/60 OD. Five weeks later, BCVA was 20/40 and Intraocular pressures (IOP) was 12 mmHg OD. CONCLUSIONS AND IMPORTANCE: Intravitreal triamcinolone injection may be a cause of AMN with cystoid macular edema (CME) and borderline-high intraocular pressure. Brimonidine may be an effective treatment for these patients in the early course of the disease.
Lennikov A, Yang M, Chang K, Pan L, Saddala MS, Lee C, Ashok A, Cho K-S, Utheim TP, Chen DF. Direct modulation of microglial function by electrical field. Front Cell Dev Biol 2022;10:980775.Abstract
Non-invasive electric stimulation (ES) employing a low-intensity electric current presents a potential therapeutic modality that can be applied for treating retinal and brain neurodegenerative disorders. As neurons are known to respond directly to ES, the effects of ES on glia cells are poorly studied. A key question is if ES directly mediates microglial function or modulates their activity merely via neuron-glial signaling. Here, we demonstrated the direct effects of ES on microglia in the BV-2 cells-an immortalized murine microglial cell line. The low current ES in a biphasic ramp waveform, but not that of rectangular or sine waveforms, significantly suppressed the motility and migration of BV-2 microglia in culture without causing cytotoxicity. This was associated with diminished cytoskeleton reorganization and microvilli formation in BV-2 cultures, as demonstrated by immunostaining of cytoskeletal proteins, F-actin and β-tubulin, and scanning electron microscopy. Moreover, ES of a ramp waveform reduced microglial phagocytosis of fluorescent zymosan particles and suppressed lipopolysaccharide (LPS)-induced pro-inflammatory cytokine expression in BV-2 cells as shown by Proteome Profiler Mouse Cytokine Array. The results of quantitative PCR and immunostaining for cyclooxygenase-2, Interleukin 6, and Tumor Necrosis Factor-α corroborated the direct suppression of LPS-induced microglial responses by a ramp ES. Transcriptome profiling further demonstrated that ramp ES effectively suppressed nearly half of the LPS-induced genes, primarily relating to cellular motility, energy metabolism, and calcium signaling. Our results reveal a direct modulatory effect of ES on previously thought electrically "non-responsive" microglia and suggest a new avenue of employing ES for anti-inflammatory therapy.
Vemula SK, Kim SA, Muvavarirwa T, Bell JL, Whitman MC. Impaired Extraocular Muscle Innervation Is Present Before Eye Opening in a Mouse Model of Infantile Nystagmus Syndrome. Invest Ophthalmol Vis Sci 2022;63(10):4.Abstract
Purpose: To determine if extraocular muscles (EOMs) from mice with nystagmus show abnormalities in myofiber composition and innervation, as seen in EOMs from human nystagmus patients, and to determine when in development those changes occur. Methods: Balb/c albino mice were crossed to pigmented mice to generate heterozygous mice, which were mated to create experimental litters containing albinos and wild-type controls. Orbits were harvested from adult animals (12 weeks old); on postnatal day (P)0, P10, P14, and P21; and from 6-week-old animals. EOM sections were collected from the intraorbital portion of the muscles. Sections were immunostained for slow and fast myosin and for neuromuscular junctions (NMJs). The proportion of each myofiber subtype and the density and size of NMJs were quantified. Initial innervation patterns were assessed using whole-mount immunostaining of embryonic day (E)13.5 embryos expressing IslMN:GFP. Results: Adult albino EOMs display an increased proportion of slow myofibers, larger slow myofibers, and a decreased density of NMJs-similar to human nystagmus patients. The percentage of NMJs on slow myofibers is also lower in albino animals. The initial innervation pattern of the incoming ocular motor neurons is normal in E13.5 albino embryos. Differences in the proportion of slow and fast myofiber subtypes are present as early as P14, and a lower percentage of NMJs on slow myofibers is present by P21. There is a lower density of NMJs on albino EOMs as early as P10, prior to eye opening. Conclusions: Changes in NMJ development observed before eye opening indicate that nystagmus is not solely secondary to poor vision.
Farhat W, Yeung V, Ross A, Kahale F, Boychev N, Kuang L, Chen L, Ciolino JB. Advances in biomaterials for the treatment of retinoblastoma. Biomater Sci 2022;10(19):5391-5429.Abstract
Retinoblastoma is the most common primary intraocular malignancy in children. Although traditional chemotherapy has shown some success in retinoblastoma management, there are several shortcomings to this approach, including inadequate pharmacokinetic parameters, multidrug resistance, low therapeutic efficiency, nonspecific targeting, and the need for adjuvant therapy, among others. The revolutionary developments in biomaterials for drug delivery have enabled breakthroughs in cancer management. Today, biomaterials are playing a crucial role in developing more efficacious retinoblastoma treatments. The key goal in the evolution of drug delivery biomaterials for retinoblastoma therapy is to resolve delivery-associated obstacles and lower nonlocal exposure while ameliorating certain adverse effects. In this review, we will first delve into the historical perspective of retinoblastoma with a focus on the classical treatments currently used in clinics to enhance patients' quality of life and survival rate. As we move along, we will discuss biomaterials for drug delivery applications. Various aspects of biomaterials for drug delivery will be dissected, including their features and recent advances. In accordance with the current advances in biomaterials, we will deliver a synopsis on the novel chemotherapeutic drug delivery strategies and evaluate these approaches to gain new insights into retinoblastoma treatment.
Sanjurjo-Soriano C, Erkilic N, Damodar K, Boukhaddaoui H, Diakatou M, Garita-Hernandez M, Mamaeva D, Dubois G, Jazouli Z, Jimenez-Medina C, Goureau O, Meunier I, Kalatzis V. Retinoic acid delays initial photoreceptor differentiation and results in a highly structured mature retinal organoid. Stem Cell Res Ther 2022;13(1):478.Abstract
BACKGROUND: Human-induced pluripotent stem cell-derived retinal organoids are a valuable tool for disease modelling and therapeutic development. Many efforts have been made over the last decade to optimise protocols for the generation of organoids that correctly mimic the human retina. Most protocols use common media supplements; however, protocol-dependent variability impacts data interpretation. To date, the lack of a systematic comparison of a given protocol with or without supplements makes it difficult to determine how they influence the differentiation process and morphology of the retinal organoids. METHODS: A 2D-3D differentiation method was used to generate retinal organoids, which were cultured with or without the most commonly used media supplements, notably retinoic acid. Gene expression was assayed using qPCR analysis, protein expression using immunofluorescence studies, ultrastructure using electron microscopy and 3D morphology using confocal and biphoton microscopy of whole organoids. RESULTS: Retinoic acid delayed the initial stages of differentiation by modulating photoreceptor gene expression. At later stages, the presence of retinoic acid led to the generation of mature retinal organoids with a well-structured stratified photoreceptor layer containing a predominant rod population. By contrast, the absence of retinoic acid led to cone-rich organoids with a less organised and non-stratified photoreceptor layer. CONCLUSIONS: This study proves the importance of supplemented media for culturing retinal organoids. More importantly, we demonstrate for the first time that the role of retinoic acid goes beyond inducing a rod cell fate to enhancing the organisation of the photoreceptor layer of the mature organoid.