A dacryocystocele or timo cyst is a benign, bluish-gray mass in the inferomedial canthus that forms as a result of a narrowing or obstruction of the nasolacrimal duct, usually during prenatal development. The prevalence of dacryocystocele is 1 in 3884 live births.
The diagnosis can be made prenatally; routine obstetric ultrasound can identify the characteristic hypoechoic lesion inferior and medial to the globe. It is important to distinguish a dacrocystocele from the more serious encephalocele, which is a neural tube defect.
A dacryocystocele can be diagnosed postpartum with a non-invasive ultrasound (US). Timo cysts may spontaneously resolve or with pressure directed toward the nose; however, nasolacrimal duct probing may be required to open the obstruction. While usually filled with sterile mucus, dacryocystoceles occasionally become infected dacryocystitis.