Cytomegalovirus
Avindra Nath, Joseph R. Berger in Clinical Neurovirology, 2020
Symptomatic congenital cytomegalic inclusion disease is characterized by disease of the central nervous system, including intracranial calcifications, microcephaly and ventriculomegaly, with or without ophthalmic and auditory damage [7,22]. Ill babies may have an array of clinical findings, including jaundice, hepatitis, hepatosplenomegaly, pneumonitis, petechiae, thrombocytopenia, hemolytic anemia, chorioretinitis, dental defects, and fetal growth retardation. Neurological findings include mental retardation, microcephaly, and other brain defects; abnormal eye development, including ocular atrophy and chorioretinitis; motor deficits, including paresis and paralysis; and seizures, including the infantile spasm syndrome [20]. Mortality may be as high as 30% and most survivors will suffer permanent neurodevelopmental sequelae, including retardation, behavioral problems, visual defects, and hearing loss.
The eye
Angus Clarke, Alex Murray, Julian Sampson in Harper's Practical Genetic Counselling, 2019
Microphthalmos and anophthalmos constitute an extremely heterogeneous group. Unilateral cases are frequently non-genetic but cannot be securely distinguished from genetic forms. Rubella, toxoplasmosis, maternal thalidomide and other drug exposures are possible causes of bilateral disease. Mental retardation is frequently associated, and microphthalmos is a feature of several chromosomal defects as well as Mendelian syndromes. The X-linked Lenz syndrome of microphthalmos with cataract, mental retardation and digital and genitourinary abnormalities must be considered. Microphthalmos with coloboma is usually autosomal dominant (in the absence of known external causes) and is heterogeneous. Complete bilateral anophthalmia can be difficult to distinguish from extreme microphthalmos and may result from environmental factors. Cryptophthalmos, with absent palpebral fissures, may be part of the previously mentioned disorders, or may occur with relatively normal eye development, usually following autosomal recessive inheritance. Some cases are part of the more general Fraser syndrome (autosomal recessive), where renal agenesis and laryngeal atresia may be major features, and where a specific developmental gene defect is known.
An overview of human pluripotent stem cell applications for the understanding and treatment of blindness
John Ravenscroft in The Routledge Handbook of Visual Impairment, 2019
Presently, research on optic neuropathies is hampered by paucity of both readily available RGCs from living patients and in vitro RGC models. However, these issues may be addressed by use of hPSCs (Chamling, Sluch and Zack, 2016; Riazifar et al., 2014). Various protocols have been established for the generation of RGCs from stem cells (reviewed in Gill et al., 2014). Multiple groups, including ours, have focused on developing efficient and robust hPSC-derived RGC differentiation protocols (Gill et al., 2016; Huang et al., 2017; Reichman et al., 2014; Riazifar et al., 2014; Sluch et al., 2015). Differentiation protocols typically rely on modulation of several cellular signalling pathways known to be involved in embryogenesis and early eye development in order to obtain retinal progenitor cells, RGCs and then enrichment of RGCs by cell sorting (Gill et al., 2016; Sluch et al., 2015). Those RGC populations show functionality and marker profiles with close resemblance to native RGCs (Gill et al., 2016; Sluch et al., 2015). Single cell RNA sequencing analysis of RGCs differentiated and enriched by selection with the sensory neuron marker THY1 through our method has revealed three main subpopulations within the hPSC-derived RGCs (Daniszewski et al., 2018).
Aplasia of the Optic Nerve: A Report of Seven Cases
Published in Neuro-Ophthalmology, 2020
Yujia Zhou, Maura E. Ryan, Marilyn B. Mets, Hawke H. Yoon, Bahram Rahmani, Sudhi P. Kurup
Optic nerve aplasia (ONA) is a rare congenital condition characterised by the absence of optic nerve and disc, central retinal vessels, and retinal ganglion cells.1,2 There is no unified aetiology to the mechanisms of ONA. Proper proliferation and apoptosis of retinal ganglion cells (RGC) are important for the development of the optic nerve.3,4 ONA can be a result of primary agenesis or secondary degeneration of RGC during the third to fourth month of gestation due to failure of retinal angiogenesis.1,5 The optic vesicle starts to invaginate at the early stage of eye development and an optic fissure is formed to allow the hyaloid arteries to enter the retina. Failure of this process disrupts retinal vasculature, which is consistent with retinal abnormalities in ONA.3 It is suggested that the failure of neural retina formation may be responsible for disruption of optic nerve development and disorganisation of other ocular tissues in ONA.6 Pax-6 is expressed in the CNS, optic stalk, retinal progenitors, and RGC, and its mutations are likely disruptive to the optic nerve and other ocular structures.7
The Development, Growth, and Regeneration of the Crystalline Lens: A Review
Published in Current Eye Research, 2020
The processes by which de novo and LEC mediated lens regeneration occur can only be understood when placed within the context of the embryologic development and subsequent growth of the lenticular organ. In early eye development the lens is formed by the invagination and closure of the surface ectoderm. The surrounding surface ectodermal tissue goes on to differentiate into the cornea; and the iris and ciliary body differentiate from nearby neural ectoderm.5 With the total removal of the lens organ, de novo regeneration necessitates the new lens tissue to emerge from the transdifferentiation of other surrounding tissues. The conditions necessary to induce the different forms of de novo lens regeneration and the processes by which they occur are informed by the primordial tissues from which the transdifferentiating tissue arises.1,6
Longitudinal Analysis of Refractive Errors in Premature Children during the First Three Years of Life
Published in Journal of Binocular Vision and Ocular Motility, 2020
Lauren Hennein, Alejandra de Alba Campomanes
Amblyopia can be caused by strabismus, visual deprivation such as media opacities and ptosis, and amblyopogenic refractive errors including visually significant myopia, hyperopia, astigmatism, and anisometropia. In the United States, vision screening typically occurs between three and five years of age in an otherwise healthy child. Eye development and subsequent emmetropization may be influenced by prematurity.1–3 Even in the absence of retinopathy of prematurity (ROP), prematurity may lead to an increased risk of amblyopogenic refractive errors.4–11 Both premature children with and without ROP have been shown to be susceptible to myopia,12–15 astigmatism,1 and anisometropia9,11 compared to full-term children. Screening children for amblyopia and amblyopia risk factors (ARFs), followed by appropriate treatment, has been shown to improve visual outcomes.13 Treatment efficacy decreases as children age, and vision loss from amblyopia can be irreversible if it is not diagnosed and treated early.14
Related Knowledge Centers
- Ectoderm
- Mesenchyme
- Mesoderm
- Neural Crest
- Optic Nerve
- Retina
- Embryo
- Ciliary Body
- Neuroepithelial Cell
- Iris