20-MHz ultrasound and its value in imaging of lacrimal plugs.

BACKGROUND High-frequency B scan ultrasonography is a proven method for the assessment of anterior segment diseases. Only few studies have used sonography to examine the lacrimal drainage system. We examined the proximal lacrimal drainage system by high-resolution 20-MHz ultrasound to verify the possibility to identify intracanalicular lacrimal plugs. METHODS Eight patients who had received 12 lacrimal plug implants were examined by high-resolution ultrasound. A 20-MHz sector scanner was used for detection and localization of 2 types of intracanalicular plugs (Herrick) lacrimal silicone plug, Smart trade mark acrylic polymer plug) and 1 punctum plug. Ultrasound examinations were performed 1-24 months after plug placement. Cross-sections of the lacrimal canaliculi were obtained. RESULTS The various intracanalicular implants were successfully viewed using the 20-MHz ultrasound sector scanner. Intracanalicular plugs were located at the appropriate position as intended. The silicone plugs could be seen as areas of higher reflectivity. In contrast, acrylic polymer plugs were seen as low-reflective inner structures. In a longitudinal echogram, the interface between the acrylic polymer plug and the lacrimal canaliculus produced a strong acoustic impedance. In patients with an intracanalicular acrylic polymer plug, the caliber of the plug could be ascertained and the diameter measured. CONCLUSION High-resolution ultrasound with a 20-MHz sector scanner is helpful in detecting intracanalicular plugs and is a valuable tool to assess the migration of lacrimal plugs through lacrimal canaliculi. A 20-MHz sector scanner can be used to identify and locate lacrimal plugs in the proximal drainage system even if biomicroscopic signs or clinical data are absent.