Aniridia

ANIRIDIA (from Greek a- negative particle and iris - rainbow), or irideremia, the absence of the iris, complete (a. totalis) or partial (a. partialis), is usually a congenital condition, although it may also result from the tearing away of the iris after trauma (a. traumatica). Congenital aniridia is often accompanied by other changes in the eye: opacities of the cornea, lens (in the form of cataracts—polar, zonular, partial, complete); dislocations and subluxations of the lens, its colobomas; opacities of the vitreous body, persistent hyaloid artery, underdevelopment of the retina, in particular its central fovea; nystagmus, and refraction anomalies. Visual acuity in aniridia is usually reduced both as a result of light scattering and blinding with a wide pupil, and due to the aforementioned concomitant changes. Clinically, in typical cases of complete aniridia, the iris is completely invisible; however, pathological-anatomical studies have established the presence of a narrow rudimentary iris hidden behind the limbus of the cornea. Because of this, aniridia does not preclude glaucoma; the latter has sometimes been observed in aniridia. Partial aniridia is the absence of the iris along a greater or lesser significant extent of its circumference, and even in the preserved part, the iris may be narrow and rudimentary. Partial aniridias approach atypical colobomas of the iris in their form. The literature emphasizes the role of heredity in the origin of aniridia (cases of its presence in three to four successive generations). There are several views on the etiology of aniridia. According to Manz, the cause of aniridia formation is adhesions of the lens with the cornea in the embryo, which prevent the growth and advancement between them of the later-developing iris. According to Duyse (v. Duyse), the occurrence of aniridia is explained by the pressure of the amnion on the surface of the optic vesicle and the resulting delay in the development of the iris. Of later authors, some support the view of aniridia as one of the hereditary developmental anomalies, with some considering the basis for the development of such anomalies to be developmental anomalies of the ectodermal rudiments of the eye, i.e., the retina. Others defend the toxic theory, based on the experimental production in young rabbits and guinea pigs (when feeding their parents with naphthalene) of a whole series of developmental anomalies, among them colobomas of the iris and choroid. Finally, it is also pointed out that the influence of radiant energy, in the form of X-rays, on pregnant animals can also manifest in various developmental anomalies of the eye. To reduce photophobia in persons suffering from aniridia, smoked glasses or special diaphragmatic glasses by Königshofer are recommended.