Double‐hump sign on gonioscopy: definitive plateau iris? A cross‐sectional study using ultrasound biomicroscopy

Purpose Plateau iris configuration (PIC) is a rare condition involving an angle closure unrelated to pupillary block. It may be defined by a narrow angle and a double‐hump configuration on gonioscopy. Plateau iris syndrome (PIS) may lead to acute angle‐closure glaucoma due to an anterior displacement and rotation of the ciliary body. It has been proposed that ultrasound biomicroscopy (UBM) is helpful in PIC/PIS diagnosis. Our work aims to describe UBM quantitative and qualitative findings in patients whose gonioscopy suggested a PIC/PIS Methods Cross‐sectional study involving patients with a double hump gonioscopic finding. UBM was then performed by a blinded observer and evaluated for the presence of following ultrasonographic (US) criteria: (1) a thick and flat iris, (2) a sharp, square root angulation on its insertion, (3) an anterior rotation of the ciliary body, (4) irido‐ciliary sulcus narrowing, (5) iris‐trabecular apposition and (6) a relatively normal anterior chamber (AC) depth. Only high‐quality images were accepted Results From September 14 to May 15, 35 patients (59 eyes) were recruited. Only 3 eyes presented the six US criteria, 23 eyes filled five of the criteria, 13 satisfied four criteria, 16 presented three criteria and 4 two criteria. The most commonly verified criteria (over 95% of them) were a thick and flat iris and a square root insertion. There was no association between any of these criteria and sex nor age (p > 0.10). Furthermore, the presence/absence of these criteria did not correlate with either anterior chamber depth, lens vault and lens length (p > 0.10) Conclusions The majority of patients presenting with clinical iris plateau syndrome do not fulfill the entire US criteria for this condition. However, the US‐based iris morphological parameters seem to be present in nearly all iris plateau patients.