THE ROLE OF ULTRASOUND BIOMICROSCOPY DISCLOSING ANGLE CLOSURE PATHOPHYSIOLOGY

To illustrate different clinical presentations of angle closure in which ultrasound biomicroscopy (UBM) was important for their etiologic classification and to analyse its usefulness in our clinical practice with the increasing use of Optical Coherence Tomography (OCT).

Tertiary-care Hospital – Centro Hospitalar Lisboa Ocidental (Lisbon, Portugal)

We present four female patients referenced to Glaucoma Subspeciality Consult (age range 52-74 years) due to elevated intraocular pressure. Following observation, these patients underwent UBM, and an angle closure mechanism was disclosed.

UBM revealed, in each case, the presence of phacomorphic glaucoma, primary pupillary block, plateau iris and uveal effusion with ciliary block. We describe the UBM imaging characteristics of iridotrabecular contact for each case.
UBM allows a quantitative and qualitative, dynamic 360-degree very informative evaluation of angle structures, and helps understanding the pathophysiologic mechanisms determining angle closure. However, it is operator-dependent and requires patient collaboration for optimal outcomes.
Anterior Segment OCT (AS-OCT), a non-contact fast acquisition exam, also offers comprehensive analysis of variations in anterior segment structures and allows determination of quantitative angle biometric parameters. The latter are highly dependent on correct scleral spur morphologic identification and unlike UBM, AS-OCT provides little detail on structures behind the iris pigment epithelium, such as the ciliary body. Moreover, some cases may present with mixed angle closure mechanisms, which may be difficult to interpret in AS-OCT imaging.

Although UBM and AS-OCT remain complementary to gonioscopy in anterior chamber evaluation, they additionally offer high resolution visualization of anatomical structures of iridociliary sulcus with an emphasis for UBM. This work illustrates how UBM can dynamically reveal the structures involved in the pathophysiologic mechanism of angle closure and lead to the most effective treatment.