Anterior segment mesenchymal dysgenesis, or simply anterior segment dysgenesis, is a failure of the normal development of the tissues of the
anterior segment
The anterior segment or anterior cavity is the front third of the eye that includes the structures in front of the vitreous humour: the cornea, iris, ciliary body, and lens
A lens is a transmissive optical device that focuses or dispers ...
of the eye. It leads to anomalies in the structure of the mature anterior segment, associated with an increased risk of
glaucoma
Glaucoma is a group of eye diseases that can lead to damage of the optic nerve. The optic nerve transmits visual information from the eye to the brain. Glaucoma may cause vision loss if left untreated. It has been called the "silent thief of ...
and
corneal opacity
Corneal opacification is a term used when the human cornea loses its transparency. The term corneal opacity is used particularly for the loss of transparency of cornea due to scarring. Transparency of the cornea is dependent on the uniform diamete ...
.
Peters' (frequently misspelled as Peter's) anomaly is a specific type of
mesenchymal
Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood, or bone. The interactions between mesenchyme and epithelium help to form nearly ever ...
anterior segment dysgenesis, in which there is central corneal leukoma, adhesions of the
iris and
cornea
The cornea is the transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the cornea ...
and abnormalities of the posterior
corneal stroma
The stroma of the cornea (or substantia propria) is a fibrous, tough, unyielding, perfectly transparent and the thickest layer of the cornea of the eye. It is between Bowman's layer anteriorly, and Descemet's membrane posteriorly.
At its centre, ...
,
Descemet's membrane
Descemet's membrane ( or the Descemet membrane) is the basement membrane that lies between the corneal proper substance, also called stroma, and the endothelial layer of the cornea. It is composed of different kinds of collagen (Type IV and VIII ...
,
corneal endothelium
The corneal endothelium is a single layer of endothelial cells on the inner surface of the cornea. It faces the chamber formed between the cornea and the iris.
The corneal endothelium are specialized, flattened, mitochondria-rich cells that ...
,
lens
A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'') ...
and
anterior chamber
The anterior chamber ( AC) is the aqueous humor-filled space inside the eye between the iris and the cornea's innermost surface, the endothelium. Hyphema, anterior uveitis and glaucoma are three main pathologies in this area. In hyphema, ...
.
Pathophysiology
Several gene mutations have been identified underlying these anomalies, with the majority of anterior segment dysgenesis genes encoding
transcriptional regulators
Regulation of gene expression, or gene regulation, includes a wide range of mechanisms that are used by cells to increase or decrease the production of specific gene products (protein or RNA). Sophisticated programs of gene expression are wide ...
. In this review, the role of the anterior segment dysgenesis genes ''
PITX2'' and ''
FOXC1'' is considered in relation to the embryology of the anterior segment, the biochemical function of these proteins, and their role in development and disease aetiology. The emerging view is that these genes act in concert to specify a population of mesenchymal progenitor cells, mainly of
neural crest
The neural crest is a ridge-like structure that is formed transiently between the epidermal ectoderm and neural plate during vertebrate development. Neural crest cells originate from this structure through the epithelial-mesenchymal transition, ...
origin, as they migrate anteriorly around the embryonic
optic cup. These same genes then regulate
mesenchymal cell
Mesenchymal stem cells (MSCs), also known as mesenchymal stromal cells or medicinal signaling cells, are multipotent stromal cells that can differentiate into a variety of cell types, including osteoblasts (bone cells), chondrocytes (cartilage c ...
differentiation to give rise to distinct anterior segment tissues. Development appears critically sensitive to
gene dosage, and variation in the normal level of
transcription factor
In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription (genetics), transcription of genetics, genetic information from DNA to messenger RNA, by binding t ...
activity causes a range of anterior segment anomalies. Interplay between ''PITX2'' and ''FOXC1'' in the development of different anterior segment tissues may partly explain the phenotypic variability and the genetic heterogeneity characteristic of anterior segment dysgenesis. In the most recent research, the ''PAX6'' gene has been implicated in Peters' Anomaly.
Diagnosis
Management
There is no standard treatment approval, yet numerous surgical techniques have been tried during the latest years, including: penetrating keratoplasty, cataract aspiration or lensectomy, optical iridectomy, selective endothelial removal, trabeculectomy and implant of glaucoma draining devices. However, postoperative outcomes are not very promising due to severe amblyopia and other ocular complications, including glaucoma or retinal detachment.
History
This congenital anomaly was first described by German ophthalmologist Albert Peters (1862–1938).
References
External links
{{Transcription factor/coregulator deficiencies
Eye diseases
Diseases named after discoverers