[Ultrasound biomicroscopy and physiopathology of congenital iris cysts]

Iris epithelial cysts, congenital or acquired, are rare tumors of the anterior chamber. The use of ultrasound biomicroscopy (UBM) and high-resolution echography (50 MHz) specified the diagnosis and confirmed the developmental hypothesis.

UBM examination with general anesthesia can provide very good vision of cysts and iris structure similar to histological examination. Successive slices are systematically produced. We report two cases: one in a 3-month-old boy with a pupillary type of pigment epithelial cyst and one in a 23-month-old boy with stromal iris cyst provides new information on iris cysts.

UBM can clearly differentiate two types of cyst, with results similar to histological slice examination. UBM slices of iris edge cysts show small cellular parietal groups with stromal echogenicity, with no visible tissular continuity. The stromal cyst has no particularity and no echogenicity.

The pupillary type of pigment epithelial cyst was generally recognized very early. The great majority of primary iris cysts, particularly those that arise from the iris pigment epithelial layers, are stable lesions that rarely progress or cause visual complications. Their slow progression could be explained by embryological history. Based on a comparison between the aspects of the two observations, the absence of enlargement of the cyst could be explained by the developmental mechanism.

The advantage of the UBM in diagnosis is confirmed for very young patients, but also in developmental investigations. These case reports also corroborate the migration cellular theory during eye development to explain the appearance of the pupillary type of pigment epithelial cyst.