![]() This non-invasive imaging technique is capable of providing high-quality cross-sectional images based on the reflectance of tissue using a near-infrared light, in contrast to UBM that uses sound. Optical coherence tomography (OCT) is a widely used imaging device in ophthalmology and has been evolving since its first publication in 1991 by Huang et al. However in the case of a cyclodialysis cleft where the angle may appear closed to the observer, UBM is particularly useful in the localization of the cleft.Īnterior segment – Optical Coherence Tomography Background Its disadvantages are the need for direct contact of the transducer to the eye or through immersion technique, which requires the patient to be in supine position and may falsely widen the anterior chamber, and its acquisition are patient- and operator-dependent. Additionally, UBM can be used for clinical diagnosis and management of anterior ocular trauma, anterior segment cysts and neoplasms, uveitis/scleritis, localization of IOL implants in suspected uveitis-glaucoma-hyphema syndrome, and planning for secondary IOL implantation, among other uses. In contrast, the resolution does not allow a high intralesional detailing with this modality. It can improve detection of invasion to adjacent structure since it is able to identify the posterior margin identification, even in densely pigmented tumors or cases with corneal opacities in anterior chamber tumors. UBM is particularly important in the diagnosis and management of ocular surface tumors. Therefore, none of the current AS imaging modalities should be considered a substitution for gonioscopy, rather as a complimentary tool in glaucoma. Īlthough UBM provides high quality images and a close agreement with gonioscopy, the latter remains the gold standard to diagnose narrow angle and angle closure allowing direct visualization of structures to assess the presence and extent of PAS and differentiating from iridotrabecular apposition. It can also distinguish between different types of angle closure, including pupillary block, plateau iris and lens-related. UBM can describe the presence of angle closure glaucoma, which is indicated by irido-corneal contact anterior to the scleral spur. Analysis and interpretation of images begins with identification of the scleral spur, a protrusion of the sclera into the anterior chamber that attaches anteriorly to the trabecular meshwork. įurther, UBM is frequently used in research to better understand the angle and can be used for qualitative analysis of the anterior chamber angle (ACA). UBM is particularly useful to confirm presence of iris plateau which has been shown in approximately 33% of patients after laser iridotomy for PACG treatment, an important group of patients that need closer follow-up due to the higher risk of peripheral anterior synechia (PAS) formation and further angle closure. In primary angle closure glaucoma (PACG), the AOD and ACD are significantly decreased and can assist in diagnosis. Lens vault, the distance of the lens located anterior to the perpendicular line between the scleral spurs.Anterior chamber depth (ACD), the distance between the central corneal endothelium and the anterior surface of the lens.Angle recess area (ARA), the triangular area bound between the AOD line and the angle recess.Angle opening distance (AOD), the perpendicular distance between the trabecular meshwork at a point 500um anterior to the scleral spur, and the iris. ![]() Another advantage is the ability to provide quantitative measurements of the anterior chamber angle (ACA) that are useful for accurate diagnosis and management. A high agreement between UBM, especially in a dark room, and gonioscopy has been shown in detecting iridotrabecular apposition. UBM is a useful non-invasive tool for evaluating the presence of narrow anterior chamber angles, angle closure glaucoma, and pathology of the ciliary body. UBM can be used for imaging much of the anatomy of the anterior segment, as well as associated pathologies, including angle closure glaucoma, ciliary body cysts, neoplasms, and angle trauma. This results in resolutions up to 20um axially and 50um laterally, and depth of tissue penetration is 4-5mm. Compared to regular ultrasound modalities such as A-scan or B scan (10 MHz), UBM uses a much higher frequency transducer (35-100 MHz). It was first introduced in the early 1990’s by Foster and Pavlin as a way to obtain cross-sections of the eye at microscopic resolution. Ultrasound Biomicroscopy (UBM) is a technique primarily used for imaging of the anterior segment (AS) of the eye. ![]()
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