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24 Cards in this Set
- Front
- Back
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Cataract
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main disease of the lens
- due to aging, metabolic disorders, trauma, heredity |
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How does the lens develop its spheroidal shape ?
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A band of epithelial cells, just above the equator, divide (germinitive zone)
Epithelial cells that shift below the equator elongate and differentiate into secondary fibre cells Secondary fibres are progressively added to the fibre mass throughout life – this is how the lens grows |
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Y-shaped sutures
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Y-shaped sutures form where tips of fibres meet – both anteriorly and posteriorly
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How does the lens develop its polarity and growth patterns?
- Is it determined by its position in the optic cup? |
Polarity of the lens
•Determined by position of lens in optic cup •Optic cup (vitreous) environment promotes fibre differentiation •Anterior segment (aqueous) environment promotes proliferation/maintenance of epithelial phenotype |
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Lens Inversion Experiment
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The molecule that induces fibre differentiation?
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FGF (fibroblast growth factor)
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Lens FGF composition
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lens epithelial cells Packing
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Lens transition zone
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Packaging of lens cells
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Packing of elongated lens cells and interlocking processes
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Protrusions and invaginations (e.g. ball-and sockets) arise predominantly at the angles between broad and narrow faces and between narrow faces along the length of the fibres - important for cell-cell adhesion with minimal extracellular space - strong cell-cell adhesion is critical for maintaining lens integrity during accommodation
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Lens Gap junctions
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- important for communication
Lens fiber cells have the highest concentration of gap junction plaques of any cells in the body. The fiber cells have extensive low-resistance gap junctions between cells that allow for efficient communication and exchange between the cells of the outer cortex and the more quiescent central fiber cells forming the lens nucleus. This extensive network of low resistance gap junction channels, called a syncytium, results in the uniform voltage seen throughout the lens. Connexins are the subunits that assemble the gap junctions. Gap junctions mediate the cell-cell transport of small molecules. Epithelial cells contain Cx43 and fibres have Cx 46 and Cx50 - these are present along the lateral membranes (broad sides) of the lens fiber cells. |
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Lens transparency depends on ______________
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regular packing of its components
- lens fibre cells - lens proteins (90% crystallins) |
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Localisation of crystallins
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a crystallin is a water-soluble structural protein found in the lens and the cornea of the eye accounting for the transparency of the structure
Alpha: appear first, produced by all cells (mostly epithelial cells) Beta and Gamma: produced only following initiation of prolongation |
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Accomadation
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•Lens needs to be transparent to transmit light
•Lens needs curvature to focus image •Lens needs to be able to change its curvature to focus near and far - accommodate |
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Cilliary muscle actions
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Accomodation prosection
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Aqueous and Viterous Humour Produced by...
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Anterior Chamber exit point
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Iris Muscles
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Cataract Epidemilogy
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By 70 years of age almost everyone has some degree of cataract formation - by 80 years of age many will need cataract surgery
Cataract surgery is very effective |
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Complications of cataract surgery
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•Posterior capsule opacification (PCO) remains the most common long-term complication (particularly with pediatric cataract surgery).
•Increased incidence of major blinding diseases: - glaucoma (particularly after pediatric cataract surgery) - late age-related maculopathy As we are living longer all these issues are becoming more relevant |
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Cataract Surgery procedure
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PCO
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