[Ultrasonography and computed tomography in ophthalmological practice: comparative value during exploration of the eye and orbit (author's transl)].

Ultrasonography is a completely harmless method of examining the eye and the orbit and uses light, inexpensive equipment, within the reach of any ophthalmologist, to provide excellent information concerning the eye and is also well adapted to orbital examination. Cephalic computed tomography, which uses ionizing radiation, is especially efficient in orbital investigations, but this kind of examination is only required in about 10% of cases. It requires expensive, cumbersome equipment and highly specialised staff; frequent use of this method, as well as the injection of contrast products, can be risky. The reader will find 3 tables that summarize briefly the comparative possibilities of ultrasonography and computed tomography in bulbar and orbital investigations and for biometry. A 4th table underlines the suitability of one method or the other in terms of the symptomatology. Consultation of this table could be a time-saver: the ophthalmologist would always begin with the method most likely to give the best information and not waste time doing both. As far as the globe and the orbit are concerned, ultrasonography is normally sufficient. When this method seems problematical or gives insufficient information, the investigation can easily be completed with a computed tomography. Using this method, therefore we can go some way towards limiting the irradiation of the crystalline lens (sometimes unjustified) and towards saving time and money within the Health Service.