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The intricate steps of human ocular embryology are impacted by cellular and genetic signaling pathways and a myriad of external elements that can affect pregnancy, such as environmental, metabolic, hormonal factors, medications, and intrauterine infections. This review focuses on presenting some of these factors to recognize the multifactorial nature of ocular development and highlight their clinical significance. This review is based on English-language articles sourced from PubMed, Web of Science, and Google Scholar; keywords searched included "ocular development in pregnancy," "ocular embryology," "maternal nutrition," "ophthalmic change," and "visual system development." While some animal models show the disruption of ocular embryology from these external factors, there are limited post-birth assessments in human studies. Much remains unknown about the precise mechanisms of how these external factors can disrupt normal ocular development in utero, and more significant research is needed to understand the pathophysiology of these disruptive effects further. Findings in this review emphasize the importance of additional research in understanding the dynamic association between factors impacting gestation and neonatal ocular development, particularly in the setting of limited resources.

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Highly effective cystic fibrosis (CF) transmembrane conductance regulator (CFTR) modulator therapies (HEMT), including elexacaftor-tezacaftor-ivacaftor, correct the underlying molecular defect causing CF. HEMT decreases general symptom burden by improving clinical metrics and quality of life for most people with CF (PwCF) with eligible CFTR variants. This has resulted in more pregnancies in women living with CF. All HEMT are known to be able pass through the placenta and into breast milk in mothers who continue on this therapy while pregnant and breast feeding. Toxicity studies of HEMT in young rats demonstrated infant cataracts, and case reports have reported the presence of congenital cataracts in early life exposure to HEMT. This article reviews the evidence for how HEMT influences the dynamic and interdependent processes of healthy and abnormal lens development in the context of HEMT exposure during pregnancy and breastfeeding, and raises questions that remain unanswered.

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The increasing use of cosmetics has raised widespread concerns regarding their ingredients. Cysteamine hydrochloride (CSH) is a newly identified allergenic component in cosmetics, and therefore its potential toxicity needs further elucidation. Here, we investigated the in vivo toxicity of CSH during ocular development utilizing a zebrafish model. CSH exposure was linked to smaller eyes, increased vasculature of the fundus and decreased vessel diameter in zebrafish larvae. Moreover, CSH exposure accelerated the process of vascular sprouting and enhanced the proliferation of ocular vascular endothelial cells. Diminished behavior in response to visual stimuli and ocular structural damage in zebrafish larvae after CSH treatment were confirmed by analysis of the photo-visual motor response and pathological examination, respectively. Through transcriptional assays, transgenic fluorescence photography and molecular docking analysis, we determined that CSH inhibited Notch receptor transcription, leading to an aberrant proliferation of ocular vascular endothelial cells mediated by Vegf signaling activation. This process disrupted ocular homeostasis, and induced an inflammatory response with neutrophil accumulation, in addition to the generation of high levels of reactive oxygen species, which in turn promoted the occurrence of apoptotic cells in the eye and ultimately impaired ocular structure and visual function during zebrafish development.

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The aim of this study was to examine the effect of microRNA 92b-3p (MiR92b-3p) overexpression on the embryonic development of zebrafish. A synthetic MiR92b-3p analogue (mirVana™ mimic, in vivo-ready) was injected at doses up to 5 ng/embryo into the yolk sac of embryos (2-16 cell stage). At 24 h post fertilization (hpf), the locomotor activity of the embryos was measured, and after hatching (72 hpf), the rates of malformation occurrence, hatching, and mortality were determined. Next, the larvae were fixed for histological and molecular examinations. Exposure to the MiR92b-3p mimic impaired embryonic development, leading to increased occurrence of malformations (i.e., pericardial edema, spine curvature, smaller eyes), decreased locomotor activity and hatching rate, and increased mortality. Importantly, the mimic affected retinal differentiation and lens formation during zebrafish embryogenesis, which suggests that MiR92b-3p could be an important factor in the regulation of fish embryogenesis and ocular development. The expression level of MiR92b-3p was substantially higher in the exposed larvae than in the untreated larvae, indicating that the mimic was successfully delivered to the zebrafish. Although screening of potential MiR92b-3p target genes suggested some changes in their expression levels, these results were inconclusive. Together, this study indicates that MiR92b-3p mimic impairs zebrafish embryonic development, and further research is necessary to identify the MiR92b-3p-regulated cell pathways involved in the impairment of the fish's development.

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AIM: To investigate the effect of intravitreal ranibizumab injection on ocular parameters in the treatment of retinopathy of prematurity(ROP), and analyze its relationship with birth weight(BW)and postmenstrual age(PMA).METHODS: A total of 98 premature infants who received routine ROP screening at Northwest Women's and Children's Hospital from January 1, 2016 to January 31, 2022 were selected, and they were divided into ROP group(49 cases)and non-ROP group(49 cases)according to the results of Retcam3 fundus screening. All children in ROP group were treated with intravitreal ranibizumab injection, with an average PMA of 38.02±3.03 weeks. The ocular parameters were measured at the PMA of 0 month(40 weeks±14d), 3 months(52 weeks±28d)and 6 months(64 weeks±28d), respectively.RESULTS: There was no difference in axial length(AL), anterior chamber depth(ACD), lens thickness(LT), vitreous length(VL)and central corneal thickness(CCT)between ROP group and non-ROP group at the PMA of 0 month(P>0.05); At the PMA of 3 and 6 months, ACD in ROP group was higher than that in non-ROP group, and LT was lower than that in non-ROP group(P<0.05); at the PMA of 6 months, AL and VL in ROP group were lower than those in non-ROP group(P<0.05). AL, ACD and VL were positively correlated with PMA in ROP group and non-ROP group, while CCT was negatively correlated with PMA; there was a positive correlation between LT and PMA in children without ROP. There was no correlation among LT, BW and PMA in ROP group.CONCLUSION: The ocular development of children with early ROP(PMA 0～6 months)treated by intravitreal ranibizumab injection is slower than that of premature infants without ROP, and BW and PMA are the main influencing factors of ocular parameters of premature infants.

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Objective: To compare the rate of refractive growth (RRG3) of the crystalline lens ("lens") versus the eye excluding the lens ("globe") for the fellow, noncataractous eyes of participants in the Infant Aphakia Treatment Study. Design: Retrospective cohort study. Subjects: A total of 114 children who had unilateral cataract surgery as infants were recruited. Biometric and refraction data were obtained from the normal eyes at surgery and at 1, 5, and 10 years. Subjects were included if complete data (axial length [AL], corneal power, and refraction) were available at surgery and at 10 years of age. Methods: At surgery and at 1, 5, and 10 years, AL, corneal power, and cycloplegic refraction were measured in the normal eyes. For each eye, the RRG3 was defined by linear regression of refraction at the intraocular lens (IOL) plane against log10 (age + 0.6 years). The RRG3 for the globe was based on IOL power for emmetropia; the RRG3 for the lens was based on IOL power calculated to give the observed refractions. Intraocular lens powers were calculated with the Holladay 1 formula. The means were compared with a paired 2-tailed t test, and linear regression was used to look for a correlation between RRG3 of the lens globe. Main Outcome Measures: The RRG3 of the lens and globe. Results: Complete data were available for 107 normal eyes. The mean RRG3 of the lenses was -12.0 ± 2.5 diopters (D) and the mean RRG3 of the globes was -14.1 ± 2.7 D (P < 0.001). The RRG3 of the lens correlated with the RRG3 of the globe (R 2  = 0.25, P < 0.001). Conclusions: The RRG3 was 2 D more negative in globes compared with lenses in normal eyes. Globes with a greater rate of growth tended to have lenses with a greater rate of growth.

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AIM: To investigate the ocular development of patients who had unilateral congenital cataract (CC) combined with persistent fetal vasculature (PFV). METHODS: This cross-sectional, observational study included patients who had unilateral CC and PFV and those with isolated unilateral CC. Axial length (AL), keratometry, anterior chamber depth (ACD), lens thickness, and vitreous length were obtained. The ocular biometric parameters of the affected eyes of patients with CC and PFV were compared with the fellow eyes and with the affected eyes of patients with isolated CC. RESULTS: A total of 110 patients were included and divided into 4 groups: group 1 (18 patients with CC and PFV, <24mo), group 2 (22 patients with CC and PFV, ≥24mo), group 3 (35 patients with CC, <24mo), and group 4 (35 patients with CC, ≥24mo). The ALs of the affected eyes were shorter than those of the fellow eyes in group 1 (20.02±1.06 vs 20.66±0.63 mm, P=0.025). While the ALs of the affected eyes were longer than those of the fellow eyes in group 2 (23.18±2.00 vs 22.31±1.06 mm, P=0.044) and group 4 (22.64±1.80 vs 22.02±1.01 mm, P=0.033). The keratometries of the affected eyes were steeper than those of the fellow eyes in group 2 (44.78±1.66 vs 43.83±1.38 D, P=0.041) and group 4 (43.76±1.91 vs 43.34±1.46 D, P=0.043). No difference of ACDs between two eyes was found in all groups (all P>0.05). CONCLUSION: Compared with the fellow eyes, the ALs of the eyes with unilateral CC and PFV are shorter in patients younger than 24mo and longer in those older than 24mo; the keratometries of the eyes with unilateral CC and PFV are steeper in patients older than 24mo and similar with those younger than 24mo. These findings provide further understanding of ocular development in patients with both CC and PFV.

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Visually induced changes in the expression of early growth response-1 (EGR1), FBJ osteosarcoma oncogene (FOS), and NGFI-A binding protein-2 (NAB2) appear to form a part of a retinal network fundamental to ocular growth regulation, and thus, the development of myopia (short-sightedness). However, it is unclear how environmental (visual) cues are translated into these molecular changes. One possibility is through epigenetic modifications such as DNA methylation, a known regulator of such processes. By sequencing bisulfite-converted DNA amplicons, this study examined whether changes in DNA methylation occur within specific regulatory and promoter regions of EGR1, FOS, and NAB2 during the periods of increased and decreased ocular growth in chicks. Visually induced changes in ocular growth rates were associated with single-point, but not large-scale, shifts in methylation levels within the investigated regions. Analysis of methylation pattern variability (entropy) demonstrated that the observed methylation changes are occurring within small subpopulations of retinal cells. This concurs with previous observations that EGR1 and FOS are differentially regulated at the peptide level within specific retinal cell types. Together, the findings of this study support a potential role for DNA methylation in the translation of external visual cues into molecular changes critical for ocular growth regulation and myopia development.

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PURPOSE: To examine cone density in relation to gestational and morphological parameters in the Copenhagen Child Cohort (CCC2000). METHODS: The macula was imaged using adaptive optics in 1,296 adolescents aged 16-17 years. Axial length and distance visual acuity were determined. Absolute and angular cone photoreceptor density were analysed for an 80 × 80-pixel area, 2 degrees temporal to the fovea. Association with axial length was analysed with linear regression. Correlation with visual acuity was described with a Pearson correlation coefficient. Associations of cone density with gestational parameters, maternal smoking, sex and age were analysed using multiple regression adjusted for axial length. RESULTS: Mean absolute cone density was 30,007 cones/mm2 (SD ± 3,802) and mean angular cone density was 2,383 cones/deg2 (SD ± 231). Peri- and postnatal parameters, sex and age had no statistically significant effect on cone density (p > 0.05). Absolute cone density decreased with longer axial length (-2,855 cones/mm2 per mm or -9.7% per mm, p < 0.0001). For angular density, which included a correction for the geometrical enlargement of the eye with axial length, a decrease with axial length was detectable, but it was small (-20 cones/deg2 per mm or -0.84% per mm, p = 0.009). CONCLUSIONS: The decrease in cone density per unit solid angle with increasing axial length was small, less than 1 percent per mm, indicating that expansion of the posterior pole during the development of refraction takes place without a clinically significant loss of cones. Perinatal parameters, within the spectrum presented by the study population, had no detectable effect on cone density.

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The salamander clade Eurycea from the karst regions of central Texas provides an ideal platform for comparing divergent nervous and sensory systems since some species exhibit extreme phenotypes thought to be associated with inhabiting a subterranean environment, including highly reduced eyes, while others retain an ancestral ocular phenotype appropriate for life above ground. We describe ocular morphology, comparing three salamander species representing two phenotypes-the surface-dwelling Barton Springs salamander (E. sosorum) and San Marcos salamander (E. nana) and the obligate subterranean Texas blind salamander (E. rathbuni) - in terms of structure and size of their eyes. Eyes were examined using confocal microscopy and measurements were made using ImageJ. Statistical analysis of data was carried out using R. We also provide a developmental series and track eye development and immunolocalization of Pax6 in E. sosorum and E. rathbuni. Adult histology of the surface-dwelling San Marcos salamander (E. nana) shows similarities to E. sosorum. The eyes of adults of the epigean species E. nana and E. sosorum appear fully developed with all the histological features of a fully functional eye. In contrast, the eyes of E. rathbuni adults have fewer layers, lack lenses and other features associated with vision as has been reported previously. However, in early developmental stages eye morphology did not differ significantly between E. rathbuni and E. sosorum. Parallel development is observed between the two phenotypes in terms of morphology; however, Pax6 labeling seems to decrease in the latter stages of development in E.rathbuni. We test for immunolabeling of the visual pigment proteins opsin and rhodopsin and observe immunolocalization around photoreceptor disks in E. nana and E. sosorum, but not in the subterranean E. rathbuni. Our results from examining developing salamanders suggest a combination of underdevelopment and degeneration contribute to the reduced eyes of adult E. rathbuni.

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Coloboma and microphthalmia (C/M) are related congenital eye malformations, which can cause significant visual impairment. Molecular diagnosis is challenging as the genes associated to date with C/M account for only a small percentage of cases. Overall, the genetic cause remains unknown in up to 80% of patients. High throughput DNA sequencing technologies, including whole-exome sequencing (WES), are therefore a useful and efficient tool for genetic screening and identification of new mutations and novel genes in C/M. In this study, we analyzed the DNA of 19 patients with C/M from 15 unrelated families using singleton WES and data analysis for 307 genes of interest. We identified seven novel and one recurrent potentially disease-causing variants in CRIM1, CHD7, FAT1, PTCH1, PUF60, BRPF1, and TGFB2 in 47% of our families, three of which occurred de novo. The detection rate in patients with ocular and extraocular manifestations (67%) was higher than in patients with an isolated ocular phenotype (46%). Our study highlights the significant genetic heterogeneity in C/M cohorts and emphasizes the diagnostic power of WES for the screening of patients and families with C/M.

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Since the publication of the Age-Related Eye Disease Study 2 (AREDS2) in 2013, the macular pigment carotenoids lutein (L) and zeaxanthin (Z) have become well known to both the eye care community and the public. It is a fascinating aspect of evolution that primates have repurposed photoprotective pigments and binding proteins from plants and insects to protect and enhance visual acuity. Moreover, utilization of these plant-derived nutrients has been widely embraced for preventing vision loss from age-related macular degeneration. More recently, there has been growing awareness that these nutrients can also play a role in improving visual performance in adults. On the other hand, the potential benefits of L and Z supplementation at very young ages have been underappreciated. In this review, we examine the biochemical mechanisms and supportive data for L and Z supplementation throughout the lifespan, with particular emphasis on prenatal supplementation. We propose that prenatal nutritional recommendations may aim at improving maternal and infant carotenoid status. Prenatal supplementation with L and Z might enhance infant visual development and performance and may even prevent retinopathy of prematurity, possibilities that should be examined in future clinical studies.

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The optics of the eye is the key to a functioning visual system. The exact nature of the correlation between ocular optics and eye development is not known because of the paucity of knowledge about the growth of a key optical element, the eye lens. The sophisticated optics of the lens and its gradient of refractive index provide the superior optical quality that the eye needs and which, it is thought, has a major influence on the development of proper visual function. The nature of a gradient refractive index lens, however, renders accurate measurements of its development difficult to make and has been the reason why the influence of lens growth on visual function remains largely unknown. Novel imaging techniques have made it possible to investigate growth of the eye lens in the zebrafish. This study shows measurements using X-ray Talbot interferometry of three-dimensional gradient index profiles in eye lenses of zebrafish from late larval to adult stages. The zebrafish lens shows evidence of a gradient of refractive index from the earliest stages measured and its growth suggests an apparent coincidence between periods of rapid increase in refractive index in the lens nucleus and increased expression of a particular crystallin protein group.

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During vertebrate embryonic development, a population of dorsal neural tube-derived stem cells, termed the neural crest (NC), undergo a series of morphogenetic changes and extensive migration to become a diverse array of cell types. Around the developing eye, this multipotent ocular NC cell population, called the periocular mesenchyme (POM), comprises migratory mesenchymal cells that eventually give rise to many of the elements in the anterior of the eye, such as the cornea, sclera, trabecular meshwork, and iris. Molecular cell biology and genetic analyses of congenital eye diseases have provided important information on the regulation of NC contributions to this area of the eye. Nevertheless, a complete understanding of the NC as a contributor to ocular development remains elusive. In addition, positional information during ocular NC migration and the molecular pathways that regulate end tissue differentiation have yet to be fully elucidated. Further, the clinical challenges of ocular diseases, such as Axenfeld-Rieger syndrome (ARS), Peters anomaly (PA) and primary congenital glaucoma (PCG), strongly suggest the need for better treatments. While several aspects of NC evolution have recently been reviewed, this discussion will consolidate the most recent current knowledge on the specification, migration, and contributions of the NC to ocular development, highlighting the anterior segment and the knowledge obtained from the clinical manifestations of its associated diseases. Ultimately, this knowledge can inform translational discoveries with potential for sorely needed regenerative therapies.

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Retinoic acid (RA), the active derivative of vitamin A (retinol), is an essential morphogen signaling molecule and major regulator of embryonic development. The dysregulation of RA levels during embryogenesis has been associated with numerous congenital anomalies, including craniofacial, auditory, and ocular defects. These anomalies result from disruptions in the cranial neural crest, a vertebrate-specific transient population of stem cells that contribute to the formation of diverse cell lineages and embryonic structures during development. In this review, we summarize our current knowledge of the RA-mediated regulation of cranial neural crest induction at the edge of the neural tube and the migration of these cells into the craniofacial region. Further, we discuss the role of RA in the regulation of cranial neural crest cells found within the frontonasal process, periocular mesenchyme, and pharyngeal arches, which eventually form the bones and connective tissues of the head and neck and contribute to structures in the anterior segment of the eye. We then review our understanding of the mechanisms underlying congenital craniofacial and ocular diseases caused by either the genetic or toxic disruption of RA signaling. Finally, we discuss the role of RA in maintaining neural crest-derived structures in postembryonic tissues and the implications of these studies in creating new treatments for degenerative craniofacial and ocular diseases.

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In a juvenile toxicology program, an unexpected finding of vacuolation of inner nuclear, ganglion cell, and nerve fiber layers of the retina was observed microscopically in routine Davidson's fixed and hematoxylin and eosin-stained tissue sections of eyes in beagle dogs at approximately 5 weeks of age. There was no necrosis or degeneration of the affected cells and no associated inflammation. Fluorescein angiography revealed no vascular leakage. Optical coherence tomography (OCT) indicated swollen cells in the same layers of the retina as observed at light microscopic examination. Transmission electron microscopy revealed that the retinal vacuolation likely was consistent with intracellular swelling of amacrine, horizontal, and/or bipolar cells of the inner nuclear layer as affected cells had an expanded cytoplasm but contained normal nucleus and organelles. As assessed by animal behavior and full-field electroretinography, the retinal vacuolation appeared to have no impact on visual function. Retinal vacuolation was seen in approximately 40% of dogs at 5 weeks of age using OCT and/or light microscopic examination. Because the change was transient and age related, did not result in degenerative retinal changes, and was not present in dogs older than 5 weeks of age, it was considered a background developmental observation in beagle dogs.

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Midkine (MDK) and Pleiotrophin (PTN) belong to a group of heparin-binding growth factors that has been shown to have pleiotropic functions in various biological processes during development and disease. Development of the vertebrate eye is a multistep process that involves coordinated interactions between neuronal and non-neuronal cells, but very little is known about the potential function of MDK and PTN in these processes. In this study, we demonstrate by section in situ hybridization, the spatiotemporal expression of MDK and PTN during ocular development in chick and mouse. We show that MDK and PTN are expressed in dynamic patterns that overlap in a few non-neuronal tissues in the anterior eye and in neuronal cell layers of the posterior eye. We show that the expression patterns of MDK and PTN are only conserved in a few tissues in chick and mouse but they overlap with the expression of some of their receptors LRP1, RPTPZ, ALK, NOTCH2, ITGß1, SDC1, and SDC3. The dynamic expression patterns of MDK, PTN and their receptors suggest that they function together during the multistep process of ocular development and they may play important roles in cell proliferation, adhesion, and migration of neuronal and non-neuronal cells.

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Polychlorinated biphenyls (PCBs), a class of persistent organic pollutant, are closely related to abnormal eye development in children. However, little is known regarding the role of peptides in the development of PCB-induced ocular dysplasia. To characterize the nature of PCB exposure on peptides involved in the development of the ocular system, we used liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) to detect differential expression of peptides between normal and PCB-exposed zebrafish embryos. A total of 7900 peptides were analyzed, 90 of which were differentially expressed, with 29 being up-regulated and 61 down-regulated. These peptides were investigated using ingenuity pathway analysis (IPA) and gene ontology (GO) analysis to explore their role in eye development. This study identified 18 peptides associated with the development of the optic nerve and ocular system in the PCB-exposure group, as well as 10 peptides that are located in the functional domain of their precursor proteins. These peptides provide potential biomarkers for the treatment of ocular dysplasia caused by PCBs and may help us understand the mechanism of abnormal eye development caused by organic pollutants.

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This chapter provides an overview of the early developmental origins of six ocular tissues: the cornea, lens, ciliary body, iris, neural retina, and retina pigment epithelium. Many of these tissue types are concurrently specified and undergo a complex set of morphogenetic movements that facilitate their structural interconnection. Within the context of vertebrate eye organogenesis, we also discuss the genetic hierarchies of transcription factors and signaling pathways that regulate growth, patterning, cell type specification and differentiation.

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Over recent decades, zebrafish has been established as a sophisticated vertebrate model for studying human ocular diseases due to its high fecundity, short generation time and genetic tractability. With the invention of morpholino (MO) technology, it became possible to study the genetic basis and relevant genes of ocular diseases in vivo. Many genes have been shown to be related to ocular diseases. However, the issue of specificity is the major concern in defining gene functions with MO technology. The emergence of the first- and second-generation genetic modification tools zinc-finger nucleases (ZFNs) and TAL effector nucleases (TALENs), respectively, eliminated the potential phenotypic risk induced by MOs. Nevertheless, the efficiency of these nucleases remained relatively low until the third technique, the clustered regularly interspersed short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system, was discovered. This review highlights the application of multiple genome engineering techniques, especially the CRISPR/Cas9 system, in the study of human ocular diseases in zebrafish.