Iris
cysts, both primary and secondary, are a diagnostic and treatment challenge. Primary
cysts arise either from the iris pigment epithelium or the iris stroma. Posterior pigment epithelial
cysts are subdivided according to their location as central, midzonal, and peripheral. Iris stromal
cysts are classified either as congenital or acquired. Free-floating
cysts are usually dislodged pigment epithelial
cysts. Secondary
cysts are classified according to the underlying cause as implantation
cysts,
drug-induced, uveitic,
tumor-induced, parasitic, or as
cysts associated with systemic disorders. Differential diagnosis is based on the clinical presentation and imaging. Ultrasound biomicroscopy is the gold standard for the imaging of iris
cysts, combining excellent resolution with sufficient tissue penetration. Treatment of iris
cysts depends largely on whether they become symptomatic or not. Symptoms include obstruction of the visual axis, corneal decompensation, secondary
uveitis, and secondary
glaucoma. Treatment options cover a range from simple observation to fine-needle aspiration (with or without intracystic injection of
absolute alcohol or
antimitotic agents),
laser (
argon, Nd:YAG), or surgical excision. In the past, the prevailing notion was that of a radical surgical intervention in the form of
iridectomy or iridocyclectomy. Given the high rate of recurrence, a stepwise conservative approach is currently favored by most clinicians.