الفهرس 
Ultrasound BiomiocroscopyOnly 14 pages are availabe for public view
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Abstract
With proper detection and prophylaxis, angle closure glaucoma appears to be a potentially preventable disease. Identifying persons at risk for acute angle closure attacks, as well as those prone to develop more chronic forms of angle closure remains a challenge.
A key element in this decision-making process is the assessment of the anterior chamber angle. The current reference standard is gonioscopy, which offers a detailed view of angle structures. Gonioscopy is subjective and difficult to learn. Furthermore, skill is needed to perform gonioscopy properly, particularly in older individuals who are frequently less able to sit comfortably at the slit lamp. Studies generally report moderate reproducibility, but these studies employ trained persons with extensive gonioscopy experience. The real-world situation is likely not as good. Ultrasound biomicroscopy has allowed a much deeper understanding of anterior chamber dynamics and the role of the ciliary body in angle closure. It provides high quality images of anterior segment structures, but is cumbersome to perform, requires a trained technician, and involves placing an eyecup on the eye, all of which limit its usefulness in the clinical setting. Questions still remain about reproducibility with UBM, although most reports of analyses on a single image indicate that images analysis is highly reproducible. UBM remains a tool that is largely used only at academic centers.
Four approaches to assessing the angle that do not require contact with the eye are assessment of LACD ( limbal anterior chamber depth) at the slit lamp, Scheimpflug photography, SPAC photography, and AS-OCT. LACD is a simple approach that in the published literature appears to be highly sensitive at identifying angles that are gonioscopically closed. If gonioscopy remains the reference standard for angle assessment, then strategies for screening for angle closure that employ LACD assessment may prove effective.
The Scheimpflug camera requires light to enter the angle, and therefore only gives an approximation of angle configuration. Whether it, too, could be used as a screening device for gonioscopically closed angles is unclear from the literature. The correlation with gonioscopy appears good, but image analysis requires a trained observer and substantial manipulation of the obtained image. SPAC imaging of the anterior segment also does not directly assess ACA configuration, but appears to segregate out reasonably well those with closed angles (on gonioscopy) from those with open angles. Further research will be needed to confirm these findings.
AS-OCT appears to be a promising technology for angle assessment. However, more data are needed to determine if AS-OCT can reproducibly image the angle and provide information that is clinically useful. The devices currently available allow for noncontact imaging of the ACA, and are fairly easy to operate. Furthermore, semi-automated image analyses can be performed (as with UBM). These devices cannot image the ciliary body, and this may be an important limitation since insight into angle closure mechanisms may require this. Prognosis for angle closure suspects may vary by ciliary body anatomy. However, even with these limitations, the AS-OCT appears to be an important improvement over current approaches to imaging the angle, and its place in clinical ophthalmology will become more clear as research studies are published in the coming years.
In summary, ACA assessment is challenging, but it is a key clinical activity that alters how patients with glaucoma or suspect glaucoma are treated. Gonioscopy remains the reference standard, but it is suboptimal. Newer technologies may improve our ability to assess and monitor the ACA.