What are the typical ultrasound biomicroscopy (UBM) findings in a middle‑aged hyperopic adult with aqueous misdirection (malignant) glaucoma after incisional glaucoma surgery?

UBM Findings in Aqueous Misdirection Syndrome

Ultrasound biomicroscopy in aqueous misdirection syndrome characteristically demonstrates anterior rotation of the ciliary processes, shallow or absent ciliary sulcus, and forward displacement of the lens-iris diaphragm, with or without supraciliary fluid accumulation. 1, 2

Key Diagnostic UBM Features

Primary Anatomical Abnormalities

• Anteriorly rotated ciliary processes are the hallmark finding, representing the mechanical basis for aqueous misdirection by obstructing normal posterior-to-anterior aqueous flow 3, 1, 2
• Absent or markedly reduced ciliary sulcus distinguishes aqueous misdirection from other causes of angle closure 3, 1
• Shallow or flat anterior chamber (both centrally and peripherally) despite a patent peripheral iridotomy confirms the diagnosis 1, 2
• Forward positioning of the entire lens-iris diaphragm creates the characteristic configuration 2, 4

Secondary Findings

• Supraciliary fluid accumulation may be present as a shallow fluid level in some cases, though this is not universally seen 4
• Iridocorneal angle closure results from the anterior displacement of peripheral iris 2, 5
• Posterior chamber configuration changes with obliteration or marked narrowing of the space between iris and lens 2

Why UBM is Superior for This Diagnosis

UBM provides better characterization of the posterior iris and ciliary body compared to anterior segment OCT, making it the preferred imaging modality for identifying aqueous misdirection. 3, 1

Technical Advantages

• High-frequency ultrasound (35-80 MHz) penetrates through corneal edema and opacities that commonly accompany this condition, unlike optical imaging 3, 6
• Visualization of retroiridal structures including ciliary body position and posterior chamber anatomy is superior with UBM versus AS-OCT 3, 6
• Real-time cross-sectional imaging allows dynamic assessment during the examination 3

Clinical Context

• UBM is particularly valuable in the postoperative setting where corneal edema may preclude gonioscopy or AS-OCT imaging 3
• The technology is operator-dependent and more time-consuming than AS-OCT, but this trade-off is justified by the superior diagnostic information for ciliary body pathology 3

Differential Diagnosis Using UBM

Excluding Pupillary Block

• Patent peripheral iridotomy must be confirmed, with absence of iris bombé configuration distinguishing aqueous misdirection from pupillary block 1
• UBM directly visualizes the iridotomy and posterior chamber to confirm patency 2, 5

Excluding Posterior Pushing Mechanisms

• Choroidal detachment or effusion appears as distinct suprachoroidal fluid collections, different from the ciliary body rotation seen in aqueous misdirection 1
• Suprachoroidal hemorrhage shows characteristic echogenic material in the suprachoroidal space 1
• Ciliary body edema (drug-induced or post-laser) demonstrates thickened ciliary body without the characteristic anterior rotation 1

Excluding Anterior Pulling Mechanisms

• Neovascularization or inflammatory membranes can be identified as distinct structures separate from the ciliary body abnormalities 1

Pre-operative Risk Assessment

In hyperopic eyes being considered for intraocular surgery, pre-operative UBM can identify anatomical risk factors for aqueous misdirection. 3

High-Risk Features

• Nanophthalmic eyes (axial length <20 mm, corneal diameter <11 mm) show crowded anterior segment anatomy on UBM 3, 1
• Plateau iris configuration demonstrates anteriorly positioned ciliary processes even before surgery 3
• These findings should prompt aggressive prophylactic measures during surgery 3, 1

Post-Treatment Monitoring

• Serial UBM imaging documents normalization of ciliary body position and restoration of the ciliary sulcus after successful treatment 2
• Anterior chamber deepening and posterior rotation of ciliary processes confirm resolution 2, 4
• UBM can assess trabeculectomy ostium patency when aqueous misdirection complicates filtration surgery 4

Common Pitfalls

• Assuming AS-OCT is equivalent to UBM for this diagnosis—AS-OCT cannot adequately visualize the ciliary body position, which is the key diagnostic feature 3, 1
• Failing to perform UBM when corneal edema prevents gonioscopy—UBM remains effective despite corneal opacity 3, 7
• Misinterpreting supraciliary fluid as the primary pathology rather than recognizing the ciliary body rotation as the fundamental abnormality 4
• Not obtaining pre-operative UBM in high-risk eyes (short axial length, chronic angle closure, hyperopia) undergoing glaucoma or cataract surgery 3, 1