Aniridia is the name of both a disorder and a group of disorders. This because aniridia is both an isolated ocular disease and a feature of several malformation syndromes. Absence of the iris was first reported in the early 19th century. The hallmark of the disease is bilateral iris hypoplasia which may consist of minimal loss of iris tissue with simple radial clefts, colobomas, pseudopolycoria, and correctopia, to nearly complete absence. Goniosocopy may be required to visualize tags of iris root when no iris is visible externally. Glaucoma is frequently present (~67%) and often difficult to treat. It is responsible for blindness in a significant number of patients. About 15% of patients are diagnosed with glaucoma in each decade of life but this rises to 35% among individuals 40-49 years of age. Hypoplasia and dysplasia of the fovea are likely responsible for the poor vision in many individuals. Nystagmus is frequently present. The ciliary body may also be hypoplastic.
Visual acuity varies widely. In many families it is less than 20/60 in all members and the majority have less than 20/200. Photophobia can be incapacitating. Posterior segment OCT changes suggest that outer retinal damage suggestive of a phototoxic retinopathy may also be a factor in the reduced acuity. Cataracts (congenital in >75%), ectopia lentis (bilateral in >26%), optic nerve hypoplasia, variable degrees of corneal clouding with or without a vascularized pannus, and dysgenesis of the anterior chamber angle are frequently present.
Increased corneal thickness (>600 microns) has been found in some series and should be considered when IOP measurements are made. In early stages of the disease, focal opacities are present in the basal epithelium, associated with sub-basal nerves. Dendritic cells can infiltrate the central epithelium and normal limbal palisade architecture is absent.
Meibomian gland anomalies also contribute to the corneal disease. The glands may be decreased in number and smaller in size contributing to deficiencies of the tear film and unstable surface wetting.