Intraocular gas measurement using A-scan ultrasound.

A-scan ultrasound was used to measure the position of the gas-fluid interface in eyes following vitrectomy and gas internal tamponade. Using 20 eyes of 19 patients it was found that in most instances the gas-fluid interface could be measured to within 0.5mm. The procedure was simple to perform and was well tolerated by the patients. This appears a useful way of monitoring changes in intraocular gas volume.