Lens development and disorders - clinical diagnosis and treatment

Published on May 31, 2016   31 min
0:00
This is the second lecture dealing with lens development and lens development disorders. My name is Professor Chris Lloyd. I'm a consultant ophthalmologist at Great Ormond Street Hospital in London. I'm also an honorary consultant at Manchester Royal Eye hospital and honorary professor of pediatric ophthalmology at Manchester Academic Health Sciences Center in the University of Manchester.
0:25
Congenital aphakia is an extremely rare malformation of the eye. It's usually associated with other ocular malformations. It can be caused by rubella syndrome or other early teratogenic influences during the first four weeks of gestation. It can be caused by homozygous mutations in the FOXE3 gene, as illustrated by the graphic to the right. This is a case that was published in Molecular Vision six years ago. It can also occur as a secondary phenomenon due to persistent fetal vasculature.
1:02
Microspherophakia is a clinical description of a spherical lens, a lens that is reduced in its natural dimensions. This can be caused by several conditions. These include mutations in the LTB2 gene, Weill-Marchesani syndrome, homocystinuria, and other pan-ocular disorders, like Aniridia or Axenfeld-Rieger syndrome, which cause damage to the zonule.
1:31
Lens duplication is also extremely rare. It's associated with corneal metaplasia, uveal coloboma, and cornea plana, or flattening of the cornea. It's presumed to be due to abnormal lens placode formation. The case illustrating this is published in the Indian Journal of Ophthalmology.
1:54
Lens coloboma is due to a failure of zonular development. And the absence of zonules in a sector of the lens leads to a scalloped defect, as illustrated in the graphics to the right-hand side. It can be isolated or part of the uveo-retinal coloboma phenotype. Very rarely, it can occur as a secondary phenomenon due to ciliary body medulloepithelioma.
2:22
Lenticonus and lentiglobus are descriptions of a developmental malformation of either the anterior or posterior lens surface. Lenticonus means a conical shape to the lens. Lentiglobus means a spherical shape. These two conditions overlap and are clinically difficult to differentiate. Posterior lenticonus is much more common. It usually occurs axially, i.e. Involving the central part of the lens. And it induces a myopic or astigmatic refractive error.
2:57
Posterior lentiglobus is mostly unilateral. It's not usually associated with systemic or other ocular anomalies. The unilateral type is typically not genetic. But bilateral lentiglobus is usually genetic, and it can be inherited in either an X-linked or autosomal dominant manner. Associations have been described with microcornea, Duanes syndrome, and anterior lenticonus. Cataract occurs as a secondary phenomenon due to lens fibre damage.
3:31
Posterior lenticonus is similar to lentiglobus in that most cases are usually unilateral and non-genetic. It can occur in the presence of a persistent hyaloid artery remnant. And again, cataract occurs because of damage to the lens fibres, which lie adjacent to the abnormal capsule. This is presumed to be due to osmotic changes in those lens fibers. Bilateral cases, commonly genetic, again, are the X-linked or autosomal dominant. And associations have been described with Trisomy 21, Pai syndrome, and Pierson syndrome.
4:10
Anterior lenticonus is a description of a thin central anterior capsule. And the graphic on the right, which is kindly given to me by Professor David Taylor, illustrates that. Bilateral anterior lenticonus typically occurs in Alport syndrome. And 25% of individuals with Alport syndrome have this lens abnormality. Alport syndrome is mostly X-linked, around 85%. But it can be autosomal recessive or autosomal dominant. And it's caused by mutations in the COL4A1 to COL4A6 genes. These code for type IV collagen. This leads to a basement membrane disorder. And as a result, individuals with this condition have renal problems leading to renal failure, sensory neural deafness, and other ocular anomalies, including changes in the retinal pigment epithelium. Males with X-linked COL4A5 are severely affected. Female carriers with this are only mildly affected.
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Lens development and disorders - clinical diagnosis and treatment

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