Pathology of the Head and Neck

294 M.R. Canninga-Van Dijk10Descemet’s membrane is thickened and there is reductionof the endothelial cell population. A PAS stainsometimes shows lamination of Descemet’s membrane.On the posterior surface of Descemet’s membrane, nodularexcrescences can be seen.10.3.4 Failed Previous GraftsMany corneal diseases can be treated by keratoplasty.Complications are rejection, formation of a retrocornealfibrous membrane and recurrence of the original disease.Rejection of the graft can occur immediately afterthe operation or many years later. Histologically, there isvascularisation of the corneal stroma, accompanied by alymphocytic infiltrate.Formation of retrocorneal fibrous membranes occursfollowing fibroblastic metaplasia of keratocytes at theposterior edges of the host-graft junction. This complicationis diminishing with advances in microsurgery.Over a longer period of time, recurrence of the originaldisease is common in patients with corneal dystrophies.10.4 Intraocular TissuesPathology of the intraocular tissues can be divided intodevelopmental anomalies, inflammatory processes,trauma, degeneration and tumours.10.4.1 Developmental Anomalies10.4.1.1 Congenital GlaucomaGlaucoma due to congenital malformation is rare. Associationswith systemic disorders like neurofibromatosis[8, 84, 130] and Sturge-Weber syndrome [18, 19] havebeen described. A malformation of the trabecular meshwork(goniodysgenesis) or persistence of embryonic tissuein the chamber angle causes an outflow obstruction.The corneoscleral envelope of the infant is distensible,so that a raised intraocular pressure can produce an enlargementof the globe (buphthalmos). A hypercellulartrabecular meshwork with hyaloid degeneration is thebest visible histopathological finding in those specimens[133].10.4.1.2 Retinopathy of PrematurityIn premature children requiring artificial breathingwith high oxygen pressures to survive, disordered neovascularisationat the periphery of the retina can occur[91]. A white retrolental fibrous membrane can form inthe most extreme cases, causing bilateral blindness ( retrolentalfibroplasia). At the end stage of the disease neovascularglaucoma leads to enucleation. The distortedretina is macroscopically visible, most frequently forminga straight band behind the lens. Histology showsretinal gliosis and optic atrophy [21].10.4.1.3 Persistent PrimaryHyperplastic VitreousIn the embryo, the lens is supported posteriorly by amass of vascular tissue, the primary vitreous. If this primaryvitreous fails to involute before birth, embryonicfibrovascular tissue persists in the anterior or posteriorpart of the vitreous and becomes hyperplastic. In persistentanterior primary hyperplastic vitreous, a retrolentalfibrovascular mass can penetrate the posterior lens capsuleand lens cortex, causing an autoimmune inflammatoryresponse. In persistent posterior hyperplasticprimary vitreous, the fibrovascular mass damages theoptic disc.10.4.1.4 Retinal DysplasiaFailure of organisation of the layers of the retina leadsto retinal dysplasia, in which nests of neuroblastic cellsform rosettes within the retina. Clustering of rosettesleads to thickening of the retina, which may become detached.Retinal dysplasia is a common feature of trisomy13, trisomy 18 and other chromosomal disorders. As anisolated entity, retinal dysplasia is very rare [65].10.4.1.5 AniridiaAniridia is a rare bilateral disease. It occurs as a conditionthat may be inherited as an autosomal dominantdisorder or as part of several systemic syndromes. Insome cases of aniridia, deletion of the short arm ofchromosome 11 occurs. Because this locus lies closeto the gene for nephroblastoma (Wilms’ tumour), therecognition of a child with sporadic aniridia shouldalert physicians to the increased risk of development ofWilms’ tumour [10, 23]. Histology of enucleated eyesor trabeculectomy specimens shows a rudimentaryiris, consisting of hypercellular stroma, often with anabnormal proliferation of pigment epithelium.10.4.1.6 Congenital Rubella SyndromeMaternal rubella infection during the first trimester ofpregnancy can affect the development and function ofthe entire eye. It can manifest as a congenital cataract,