OBJECTIVES: To determine the use of high-frequency ultrasound biomicroscopy (UBM) in the assessment of hypotony and in particular to determine the proportion of cases for which UBM contributed significant additional hitherto unaccessible information. PATIENTS AND METHODS: Ultrasound biomicroscopy was performed in a standard manner, using a Humphrey UBM 840 system (Humphrey Instruments, Inc., San Leandro, CA). UBM findings were analysed and the clinical relevance of UBM information was determined for the whole collective. RESULTS: Twelve patients with hypotony were examined. UBM findings contributed essential information that allowed to reach a diagnosis or that determined the therapeutic attitude in 10 of the 12 hypotonic patients. In two cases the cause of hypotony was tractional ciliary body detachment, in 5 cases it was post-inflammatory atrophy of the ciliary body, in 3 cases it was post-traumatic irido and cyclodialysis, in one case it was supraciliary and suprachoroidal effusion and in the last case it was due to uveal effusion syndrome. Based on these findings we established a schematic approach for hypotony. CONCLUSIONS: This procedure enabled us to assess the morphological changes found in patients with hypotony. In a majority of cases UBM was useful either to orient therapeutic intervention or to establish a diagnosis. On the base of our findings a schematic approach for hypotony, using UBM, was established.