Leiomyoma of the iris is a rare, benign intraocular smooth muscle tumor.  The tumor often originates from the sphincter or less commonly from the dilator muscles. Studies have found that leiomyomas occur much less frequently than previously reported. Iris leiomyoma has been previously overdiagnosed. Stricter diagnostic criteria involving electron microscopy and immunohistopathology have been added as standards for reporting.
The pathogenesis of iris leiomyoma is unclear.  Hormones are speculated to play a role in the pathogenesis due to the tumor's similarity to uterine leiomyoma (fibroids) and its predilection to females. Structures in the iris of neuroectodermal origin believed to give rise to the tumor include the sphincter muscle and the dilator muscle. Structures in the iris of mesodermal origin believed to give rise to the tumor include mesenchymal tissue.
The incidence of smooth muscle tumors has been reported as 2.3%, 4%, 9%, and 14.5%, in different published series of iris tumors.
No data on mortality and morbidity from iris leiomyoma have been reported. Morbidity may be limited to the occasional presence of secondary glaucoma and decreased vision when the mass reaches the visual axis.
This condition is reported only in white subjects.
Females are affected more frequently than males.
Cases of leiomyoma of the iris have been seen in patients aged 10-77 years.
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