Eyeworld

WINTER 2024 | EYEWORLD | 75 G Relevant disclosures Shareef: None Xu: ArcScan, Heidelberg Engineering for example, or angle closure in the setting of a patent iridotomy in the presence of plateau iris syndrome. "[Imaging] would enable the phy- sician to counsel the patient to consider argon laser iridoplasty to further open the angle to enhance outflow and lower the eye pressure," Dr. Shareef said. Dr. Xu said anterior segment OCT for glau- coma is an active area of research. "One challenge to performing gonioscopy is that it's qualitative. We describe the structures we can see but we can't take a precise measure- ment. It becomes hard to track conditions like angle narrowing or angle closure over time," he said. "OCT has been around for several decades, and it's widely used in the posterior segment for measuring anatomical structures like the thickness of the retina. We and other research groups have been adapting OCT for the anterior segment as a means of more precisely quanti- fying the anatomical configurations of our pa- tients. I think that is a unique strength of OCT, which nicely complements a primary weakness of gonioscopy. In addition, OCT is fast; it doesn't take a trained clinician to perform; it's non-con- tact so it's comfortable for patients. Analysis of OCT images can also be automated using other technologies, such as artificial intelligence. In these ways, OCT may fill a clinical need for a more convenient and reproducible method to assess the angle." Some knowledge from the research being produced with AS-OCT for angle imaging is being transferred to the clinic already. Dr. Xu said he and colleagues compared AS-OCT and gonioscopy for predicting patients with mild angle closure who would go on to develop more severe angle closure. 2 They found patients with narrow angles on AS-OCT had a higher risk of progression, whereas gonioscopy was not as predictive. He added they have yet to identify specific cutoffs at which a patient should be con- sidered higher risk and receive treatment, but this research is underway. A couple of limitations for anterior segment OCT are that it's expensive and bulky, compared to a gonio lens, which is cheaper and portable. At this point, UBM of the angle is feasible but has some limitations, according to Dr. Xu. Not only does it require a trained technician to perform, but he said there is generally no way to locate the previous location of imaging (no clear landmarks), making repeatability with measurements difficult. "It's hard to know exactly where on the eye you're imaging. From a reproducibility standpoint, if you image a patient and re-image 6 months later, you might not be in the same location and therefore you might get different measurements," he said, adding that some com- panies, like ArcScan, are working on overcom- ing this limitation. "It's not as convenient or as reproducible as AS-OCT," Dr. Xu continued of UBM. "Howev- er, it allows you to look behind the iris, which AS-OCT does not. If you have a ciliary body tumor or a cause of angle closure that originates behind the iris, you can't see that with AS-OCT." As of right now, Dr. Xu said, "we're primari- ly trying to implement OCT as a complement to gonioscopy to make clinicians' lives a bit easier and angle evaluations more precise." In the meantime, Dr. Xu and Dr. Shareef advocate for regular office-based gonioscopy on glaucoma patients. "Imaging typically provides a 2-D view of a representative angle with multiple measure- ments. Even in those technologies that offer 3-D viewing, there are certain deficiencies inherent with imaging wherein manual gonios- copy provides superior clinical information that imaging cannot," Dr. Shareef said, including identifying subtle neovascularization of the angle in patients with retinal ischemia, reliable identification of Schwabe's line and the trabec- ular meshwork to determine the angle's status, differentiating between appositional angle clo- sure vs. synechial angle closure, and confirming proper anatomic placement of microstents in Schlemm's canal postoperatively. Contact Shareef: drshareef@glaucomacc.com Xu: Benjamin.Xu@med.usc.edu In the pipeline Dr. Shareef said the ViaLux Laser System (ViaLase) combines femtosecond laser with gonioscopic imaging for non-invasive tra- beculotomy procedures. "A high-resolution video of the iridocorneal angle allows the surgeon to inspect the angle and to select the desired area of treatment to deliver the laser with minimal collateral damage to adjacent tissue," he said.

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