[Ostensible ultrasonic changes after internal tamponade of the retina with silicone oil]

Echographic control after pars plana vitrectomy (PPV) and internal tamponade of the retina with silikon oil (SO) is necessary in case of opaque optical media (bulous keratopathy, bleeding and exsudation within anterior chamber, complicated cataract). In interpretation of echographic image some difficulties or errors may be caused by physical properties of SO, as for example reduced speed of propagation of ultrasound in this media, ultrasound absorption coefficient, acoustic impedance and reflection coefficient.