Contributor: Gordon K. Klintworth
Axenfeld anomaly is part of the spectrum of anterior segment dysgenesis [dysgenesis - anterior segment]. It is characterized by a posterior embryotoxon and an undue prominence of the connective tissue bundles, which are located in Schwalbe ring between the termination of Descemet membrane and the beginning of trabecular meshwork may be seen. Strands of connective tissue extend from the ring across the anterior chamber to the iris. The combination of Axenfeld anomaly and arteriohepatic dyplasia are found in Alagille syndrome. The causes of Axenfeld syndrome include mutations in the FOXC1 gene,
A severe anterior chamber deformity, in which prominent strands are associated with marked hypoplasia of the iris stroma, constitutes Rieger anomaly. Dysgenetic endothelial cells and Descemet membrane with changes similar to those found in the corneas of congenital hereditary endothelial dystrophy have been reported in a patient with Rieger anomaly adding to the spectrum of this condition. Various abnormalities of the above-mentioned changes with dental and osseous deformities is Rieger syndrome. Persistence of mesenchymal tissue in the angle probably forms the prominent Schwalbe ring and attached iris strands. High insertion of the iris and dysgenesis of the aqueous drainage channel is causally related to the developmental glaucoma, which may have a delayed onset. Juvenile glaucoma develops in 50-70% of such eyes due to faulty development of the filtration angle. Associated corneal anomalies are usually central abnormalities termed clinically corneal leukomas. A focal absence of the corneal endothelium and Descemet membrane results in a gray to white corneal opacity. Ultrastructural examination of some cases show irregular basal epithelial cells, absence of Bowman layer, stromal edema and scarring with derangement of the lamellar architecture, collagen fibrils with a larger than normal diameter in the posterior stroma, absence of Descemet membrane, and endothelium in the central cornea. Fibrous tissue fills the defect. The main central corneal abnormalities are posterior keratoconus, Peters anomaly, and von Hippel internal corneal ulcer. Abnormal neural crest migration of the cells destined to become posterior corneal stroma, Descemet membrane and endothelium can result in this rare anomaly. Inflammation is not a feature.