Ultrasonography to assess patency of the tube in Molteno seton implantation.

It is occasionally difficult to ascertain postoperatively whether a Molteno implant is functioning or not. We have found that ultrasonography (B-scan) is a useful diagnostic tool in assessing tube patency. Polaroid images of 29 ultrasound pictures, 8 with occluded tubes, were taken postoperatively and presented independently to a radiologist and a retinal specialist, who were asked to determine the functioning state of the Molteno implant. In all cases the observers were able to correctly identify whether the tube was patent or not.