![]() Even the criteria for determining whether a patient needs a laser iridotomy for angle closure based on gonioscopy alone have not been well defined. 9 Although gonioscopy is relatively quick and easy to perform, it does not offer an easy way to precisely document the degree of angle opening. One of the most common indications for use of gonioscopy is to examine the iridocorneal angle for angle closure. 6,7 In addition, the trabecular meshwork and adjacent structures can be easily visualized by identifying the so-called TM scoop or the newly named band of extracanalicular limbal lamina, or BELL. For these applications, novel anterior segment parameters based on the location of the Schwalbe line (instead of the scleral spur) have been developed, and SD-OCT has exquisite ability to visualize Schwalbe line. Although this limits penetration through the sclera, most SD-OCT devices now have anterior segment lenses or attachments that allow imaging of the anterior segment and iridocorneal angles. The wavelength of SD-OCT devices is typically between 840 nm and 870 nm, compared with the 1,310 nm of dedicated AS-OCT devices. Therefore, purchase of a separate dedicated OCT designed only for the anterior segment is no longer necessary. Although AS-OCT cannot provide images analogous to indentation gonioscopy, taking scans with the lights on and off can offer an idea about the narrowing of the angle with lighting and the degree of pupillary constriction.įortunately, the current generation of spectral-domain OCT (SD-OCT) devices widely used by clinicians to image the posterior segment can also acquire anterior segment images. It requires no contact with the eye, can be done in complete darkness or under standardized lighting conditions, 5 and can be performed by a technician to be interpreted by the physician. Additionally, with gonioscopy, the operator may inadvertently open the angle by unintentional indentation.ĪS-OCT offers certain advantages compared with gonioscopy. ![]() Gonioscopy takes hands-on training to learn and potentially years to master, requires contact with the patient’s eye, is subjective, and requires light for visualization, which may affect angle opening. CLINICAL ADVANTAGESĭespite its recognized advantages, gonioscopy has inherent shortcomings, some of which may be significant hindrances to obtaining precise measurements. Some glaucoma specialists maintain that there is no incentive to adopt AS-OCT because gonioscopy is quick and fairly easy to perform. Furthermore, the relatively high cost of the device along with the inability to receive insurance reimbursement for the procedure (at least in the United States) were likely factors affecting the low adoption rate.Īdditionally, despite the large number of research studies showing AS-OCT to have good reproducibility and repeatability, 2-4 AS-OCT systems were meant to augment the standard gonioscopy technique rather than replace gonioscopy. The initial AS-OCT device that was introduced (Visante, Carl Zeiss Meditec) could be used only for anterior segment evaluation, and the wavelength for the scans (1,310 nm) was optimized for examination of the iridocorneal angle.
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