Iris Cyst Treated Cy Electrolysis.

CYSTS of the uveal tract have been classified clinically as congenital, parasitic, exudative or degenerative, traumatic implantation, and spontaneous or idiopathic (Duke-Elder, 1940). There is considerable overlap between the last two groups and many cases which one suspects of being traumatic in origin give no history of injury. The tissue forming the cyst in traumatic cases has been implanted either as an island or by active ingrowth of epithelium along the tract of a penetrating wound and may appear as a pearl tumour or as a serous cyst. The former is solid and greyishwhite with walls formed of stratified or cuboidal epithelium, the innermost layers of which as a rule degenerate to produce a fluid rich in fat globules and cholesterol crystals. A foreign body may be present in the lesion. The serous cyst is the more common form and may arise a few weeks or perhaps not for many years after the injury. It has a relatively thin wall of ill-developed or irregular epithelium and contains a yellowish or slightly turbid fluid. Congenital cysts of the iris are rare and may be pigmented or unpigmented. Some observers claim that all spontaneous cysts of the iris are congenital and that their apparently late appearance is due to sudden rapid dilatation leading to a rise in tension, but according to Mann (1937) this cannot be taken as certain. A diagnosis of spontaneous cyst of the iris is usually made only when all other causes have been eliminated. It may occur in the stroma or between the two epithelial layers in the posterior surface of the iris and may be pigmented or unpigmented. Stromal cysts occur mainly in young persons, 50 per cent. before 10 years of age and two-thirds before 20 years (Duke-Elder, 1940), which suggests that they may be congenital in type. After having been quiescent for years, they may suddenly start to grow and give rise to glaucoma. Various theories have been put forward to account for them. It was suggested that the unpigmented were mesoblastic cysts derived from iris endothelium, but Wolfrum (1915) has shown that the human iris has no endothelium. Mann (1937) favoured the idea that the unpigmented cysts, like the pigmented ones, are formed from the neural ectoderm of the rim of the optic cup, but at a much earlier age before it is fully pigmented. More recently, Politzer (1953) has reported histological findings on sections from four human embryos having small vesicles springing from the anterior border of the optic cup. The author thinks it likely that these may contribute to the formation of spontaneous iris cysts.