ABSTRACT The authors report the case of a male adult presenting significant ocular complications and irreversible visual impairment, resulting from the long-term progression and late diagnosis of an iris cyst in the right eye, probably secondary to trauma. The patient was admitted to Hospital Universitário Antonio Pedro with a total corneal opacity that blocked direct visualization of the anterior chamber. Ultrasound biomicroscopy was crucial for the anatomic study, and the patient was submitted to enucleation for aesthetic improvement and clarifying diagnosis. We concluded athalamia and deformation of the anterior segment, due to expansion of the cyst, led to gradual elevation of the intraocular pressure and damage of the optic nerve, resulting in visual loss.