Cataracts in Infancy

1988 ◽  
Vol 9 (7) ◽  
pp. 227-233
Author(s):  
Joseph H. Calhoun
Keyword(s):  
Basement Membrane ◽  
Spherical Cavity ◽  
Posterior Part ◽  
Crystalline Lens ◽  
Vitreous Humor ◽  
Lens Capsule ◽  
Optic Vesicle ◽  
Surface Ectoderm ◽  
Ciliary Processes ◽  
Lens Vesicle

A cataract is a loss of transparency of any size or degree in that unique organ of vision, the crystalline lens of the eye. To the layman a cataract often connotes a visually significant opacity that impairs vision and requires surgery. ANATOMY OF THE LENS The lens is a biconcave transparent organ that can alter its shape to meet different optical needs. It lies immediately posterior to the iris and just anterior to the vitreous humor. A portion of the lens is visible through the pupil. The lens is held or suspended in place by the zonules or suspensory ligaments, which arise from the reqion of the ciliary processes and attach to the equator of the lens. EMBRYOLOGY OF THE LENS The lens is unique in many ways. At about the 4-mm stage in the embroy. the surface ectoderm over the advancing optic vesicle begins to thicken, and then invaginates to form the lens pit, which later separates from the surface ectoderm to form a spherical cavity, the lens vesicle. Those cells originally on the surface of the ectoderm now line the lens vesicle surrounded by the basement membrane of these cells, the future lens capsule. By the seventh week of life, those cells on the posterior part of the vesicle have elongated and proliferated to obliterate the cavity of the lens vesicle to form the embryonic nucleus, which remains unchanged throughout life (Fig 1).

Mechanics of Optic Cup Invagination in the Embryonic Chick Eye

2012 ◽  
Author(s):  
Alina Oltean ◽  
David C. Beebe ◽  
Larry A. Taber
Keyword(s):  
Eye Development ◽  
Embryonic Chick ◽  
Optic Vesicle ◽  
Surface Ectoderm ◽  
Morphogenetic Process ◽  
Optic Cup ◽  
Optic Vesicles ◽  
Lens Vesicle ◽  
Lens Placode

Invagination of epithelia is an essential morphogenetic process that occurs in early eye development. The mechanics of the tissue forces necessary for eye invagination are not yet understood [1]. The eyes begin as two optic vesicles that grow outwards from the forebrain and adhere to the surface ectoderm. At this point of contact, both the surface ectoderm and optic vesicle thicken, forming the lens placode and retinal placode, respectively. The two placodes then bend inward to create the lens vesicle and bilayered optic cup (OC) [1, 2].

scholarly journals Lens Extrusion fromLaminin Alpha 1Mutant Zebrafish

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Mallika Pathania ◽  
Elena V. Semina ◽  
Melinda K. Duncan
Keyword(s):  
Basement Membrane ◽  
Structural Integrity ◽  
Crystalline Lens ◽  
Lens Capsule ◽  
Structural Defects ◽  
Ocular Lens ◽  
Report Analysis ◽  
Lens Material ◽  
Hyaloid Vasculature

We report analysis of the ocular lens phenotype of the recessive, larval lethal zebrafish mutant,lama1a69/a69. Previous work revealed that this mutant has a shortened body axis and eye defects including a defective hyaloid vasculature, focal corneal dysplasia, and loss of the crystalline lens. While these studies highlight the importance of lamininα1 in lens development, a detailed analysis of the lens defects seen in these mutants was not reported. In the present study, we analyze the lenticular anomalies seen in thelama1a69/a69mutants and show that the lens defects result from the anterior extrusion of lens material from the eye secondary to structural defects in the lens capsule and developing corneal epithelium associated with basement membrane loss. Our analysis provides further insights into the role of the lens capsule and corneal basement membrane in the structural integrity of the developing eye.

The upstream ectoderm enhancer in Pax6 has an important role in lens induction

Development ◽  
2001 ◽  
Vol 128 (22) ◽  
pp. 4415-4424 ◽  
Author(s):  
Patricia V. Dimanlig ◽  
Sonya C. Faber ◽  
Woytek Auerbach ◽  
Helen P. Makarenkova ◽  
Richard A. Lang
Keyword(s):  
Transcriptional Control ◽  
Control Element ◽  
Pax6 Gene ◽  
Pax6 Expression ◽  
Surface Ectoderm ◽  
Targeted Deletion ◽  
Lens Vesicle ◽  
Normal Lens ◽  
Lens Formation ◽  
Lens Placode

The Pax6 gene has a central role in development of the eye. We show, through targeted deletion in the mouse, that an ectoderm enhancer in the Pax6 gene is required for normal lens formation. Ectoderm enhancer-deficient embryos exhibit distinctive defects at every stage of lens development. These include a thinner lens placode, reduced placodal cell proliferation, and a small lens pit and lens vesicle. In addition, the lens vesicle fails to separate from the surface ectoderm and the maturing lens is smaller and shows a delay in fiber cell differentiation. Interestingly, deletion of the ectoderm enhancer does not eliminate Pax6 production in the lens placode but results in a diminished level that, in central sections, is apparent primarily on the nasal side. This argues that Pax6 expression in the lens placode is controlled by the ectoderm enhancer and at least one other transcriptional control element. It also suggests that Pax6 enhancers active in the lens placode drive expression in distinct subdomains, an assertion that is supported by the expression pattern of a lacZ reporter transgene driven by the ectoderm enhancer. Interestingly, deletion of the ectoderm enhancer causes loss of expression of Foxe3, a transcription factor gene mutated in the dysgenetic lens mouse. When combined, these data and previously published work allow us to assemble a more complete genetic pathway describing lens induction. This pathway features (1) a pre-placodal phase of Pax6 expression that is required for the activity of multiple, downstream Pax6 enhancers; (2) a later, placodal phase of Pax6 expression regulated by multiple enhancers; and (3) the Foxe3 gene in a downstream position. This pathway forms a basis for future analysis of lens induction mechanism.

The Msh-like homeobox genes define domains in the developing vertebrate eye

Development ◽  
1991 ◽  
Vol 112 (4) ◽  
pp. 1053-1061 ◽  
Author(s):  
A.P. Monaghan ◽  
D.R. Davidson ◽  
C. Sime ◽  
E. Graham ◽  
R. Baldock ◽  
...  
Keyword(s):  
Mouse Embryo ◽  
Ciliary Body ◽  
Cellular Differentiation ◽  
Temporal Relationship ◽  
Chromosomal Location ◽  
Neural Retina ◽  
Optic Vesicle ◽  
Surface Ectoderm ◽  
Optic Cup ◽  
Vertebrate Eye

The mouse Hox-7.1 gene has previously been shown to be related to the Drosophila Msh homeobox-containing gene. Here we report the isolation of a new member of this family which resides at an unlinked chromosomal location and has been designated Hox-8.1. Both Hox-7.1 and Hox-8.1 are expressed in the mouse embryo during the early stages of eye development in a distinct spatial and temporal relationship. Hox-8.1 is expressed in the surface ectoderm and in the optic vesicle before invagination occurs in regions corresponding to the prospective corneal epithelium and neural retina, respectively. Hox-7.1 is expressed after formation of the optic cup, marking the domain that will give rise to the ciliary body. The activity of these genes indicates that the inner layer of the optic cup is differentiated into three distinct compartments before overt cellular differentiation occurs. Our results suggest that these genes are involved in defining the region that gives rise to the inner layer of the optic cup and in patterning this tissue to define the iris, ciliary body and retina.

scholarly journals Observations on the shape of the lens in the eye of the silver lamprey, Ichthyomyzon unicuspis

1993 ◽  
Vol 71 (1) ◽  
pp. 34-41 ◽  
Author(s):  
Shaun P. Collin ◽  
Bernd Fritzsch
Keyword(s):  
Epithelial Cells ◽  
Basement Membrane ◽  
Single Layer ◽  
Lens Capsule ◽  
Radius Of Curvature ◽  
Dense Layer ◽  
Dorsoventral Axis ◽  
Axial Diameter ◽  
Equatorial Diameter ◽  
Lens Surface

The shape of the lens in the eye of the silver lamprey, Ichthyomyzon unicuspis was examined in live, frozen, and fixed material. Contrary to other reports, the lens was found to be nonspherical with a cone-shaped posterior. The egg-shaped lens, which contains horizontal sutures on both the anterior and posterior surfaces, is also asymmetric in the nasotemporal axis. Its equatorial diameter exceeds its axial diameter (thickness) and the radius of curvature of the lens in the dorsoventral axis is greater than the radius of curvature in the anterioposterior axis. The lens is surrounded by a thick basement membrane with the anterior lens surface covered by a single layer of cuboidal epithelial cells. Juxtaposed to the lens capsule is a dense layer of lens fibres, which stain more darkly and surround an ill-defined lens nucleus. The shape of the lens is discussed in relation to that in aquatic gnathostomes and compared with the putative multifocal lenses of some mesopelagic teleosts. It is also hypothesized that the previously reported active focussing ability of the lamprey eye may have been misinterpreted, owing to failure to take into account the nonspherical lens shape, and may reflect measurements taken of the eye and lens at different angles.

scholarly journals Developmental acquisition of basement membrane heterogeneity: type IV collagen in the avian lens capsule.

1983 ◽  
Vol 97 (3) ◽  
pp. 940-943 ◽  
Author(s):  
J M Fitch ◽  
R Mayne ◽  
T F Linsenmayer
Keyword(s):  
Basement Membrane ◽  
Type Iv Collagen ◽  
Lens Capsule ◽  
Basement Membranes ◽  
Developmentally Regulated ◽  
Membrane Heterogeneity ◽  
Domain Specific ◽  
Type Iv ◽  
Anterior Lens Capsule ◽  
Immunohistochemical Analyses

To investigate potential heterogeneity and developmental changes in basement membranes during embryogenesis, we performed immunohistochemical analyses on lens capsules in chicken embryos of different ages using domain-specific monoclonal antibodies against type IV collagen. We found that the capsule of the newly formed lens stained uniformly with antibodies against this component of basement membranes, but with increasing age and differentiation of the lens cells the anterior lens capsule remained brightly fluorescent while staining of the posterior capsule became relatively much less intense. This antero-posterior gradient of anti-type IV collagen antibody reactivity demonstrated that developmentally-regulated changes can occur within a single, continuous basement membrane.

scholarly journals Mechanical effects of the surface ectoderm on optic vesicle morphogenesis in the chick embryo

2014 ◽  
Vol 47 (16) ◽  
pp. 3837-3846 ◽  
Author(s):  
Hadi S. Hosseini ◽  
David C. Beebe ◽  
Larry A. Taber
Keyword(s):  
Chick Embryo ◽  
Optic Vesicle ◽  
Surface Ectoderm ◽  
Mechanical Effects
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