A comparative approach to anterior segment dysgenesis

Abstract

SUMMARYThe role of animal models in our developing understand ing of anterior segment dysgenesis is outlined. Research in avian models shows the importance of the neural crest in the development of the anterior segment and the fail ure of terms such as anterior segment cleavage adequately to describe the embryology of this area. Study of the anatomical differences between the anterior seg ment of the primate and that of the sub-primate mammal explains the differences seen in the dysplastic changes occurring in the iridocorneal angle in man and those occurring in sub-primate mammals such as the rabbit or the dog. Such work gives an improved understanding of congenital lesions seen ophthalmologically in man as well as those encountered in veterinary ophthalmology.The last 15 years have seen an upsurge of knowledge con cerning the embryological origins of the craniofacial region, including the eye. These new insights into the normal and abnormal patterns of craniofacial develop ment have inevitably overturned and refined cherished theories concerning the embryology of specific structures in this area. Nowhere has this been more obvious than in the anterior segment of the eye, where theories of meso dermal cleavage have been definitively demonstrated to be totally incorrect. Mesoderm is clearly not involved in the establishment of the anterior segment, which is almost completely derived from neurectoderm and neural crest. There is no cleavage: sequential migration of waves of neural crest cells establishes the corneal endothelium and stroma, iris, and angle.We now understand the embryological origins of the anterior segment development, but are by no means out of the trees with regard to a comprehensive appreciation of the genesis of the wide range of congenital, and indeed later onset abnormalities of the corneal endothelium, iris

Bilateral Buphthalmia in a 4-Month-Old Texas Longhorn Steer

“…8 Anterior segment dysgenesis (ASD) is well known in humans and has also been reported in a variety of animal species, including dog, cat, cattle, horse, llama, rabbit, and mouse. 2,4,7,12 Lesions associated with ASD in humans and animals include a wide range of anomalies, such as corneal opacities, persistent pupillary membranes, malformations of the iridocorneal angle, microphthalmia or buphthalmia, microphakia, and congenital cataracts, which can cause varying degrees of visual impairment. 4,7 Dysgenesis of components of the anterior segment have been rarely reported in cattle and include absent anterior chamber and closure of anterior chamber angles occurring in several calves over multiple years in a single herd of Brahman  Santa Gertrudis  Herefords, iris hypoplasia in albino Hereford cattle, and anterior staphyloma and rudimentary lens in a Holstein calf.…”

Duty, professionalisation and nursing knowledge

“…While the debates around the pros and cons of professionalisation rage on in nursing and medicine (Daly, Speedy & Jackson ), it is perhaps unsurprising that the veterinary healthcare sector should seek affiliation with human healthcare. As shown by interdisciplinary initiatives such as the One Health Initiative (One Health Initiative ), the cross‐fertilisation of veterinary and human surgery (Williams ) and the explicit synergies with the human paediatric nursing approaches (Williams & Jewell ), there are clear areas of interface which offer many opportunities to learn from one another.…”