Correspondence of the Dark-prone test to ultrasound biomicroscopy in the diagnosis of plateau iris syndrome: A pilot study

Background: This study evaluated the correspondence of the dark-prone provocative test to ultrasound biomicroscopy (UBM) in the diagnosis of plateau iris syndrome. Materials and methods: Patients, after undergoing a laser iridotomy to eliminate pupillary block, with UBM-confirmed plateau iris syndrome underwent the dark-prone provocative test. An increase in intraocular pressure (IOP) of 8 mmHg or more following the test was considered a positive result. Nine eyes from six patients were included in the study. Results: Eight eyes (88.9%) had elevated IOP of at least 8 mmHg following 1 hour of provocation and, therefore, a positive dark-prone provocative test. One eye had an IOP elevation of only 5 mmHg. Conclusion: There is a high level of correspondence between a positive dark-prone test and UBM in patients with plateau iris syndrome. The dark-prone test could be effective in confirming the clinical diagnosis of plateau iris syndrome.