We report the case of a 2-day-old child with buphthalmia caused by a congenital pigmented epithelial iris cyst. The use of ultrasound biomicroscopy (UBM) and high-resolution echography (20MHz) specified the diagnosis before general anesthesia for complete examination and treatment. Surgery can control intraocular pressure and the opening of the visual axis; there is, however, relative amblyopia. This case confirms the advantage of UBM in examining tumors of the anterior segment. The early diagnosis, facilitated by use of the UBM, provided quick and well-adapted treatment.