Eyeworld

I MARCH 2020 | EYEWORLD | 63 by Chiles Samaniego Contributing Writer I ntraoperative OCT expands the amount of visual information surgeons have at their disposal during any given ophthal- mic surgical procedure, well beyond that provided by the standard binocular surgical microscope. "OCT is helpful to really see the third dimension," said Oliver Findl, MD. While the binocular microscope provides a "3D impres- sion," Dr. Findl said, "at the end of the day we don't have a detailed depth resolution." The OCT provides detailed optical slices for the surgeon to examine in real time. Just how useful is this information, and what is the technology's role in practice? That's what EyeWorld discussed with Dr. Findl, Julie Schallhorn, MD, and Marie-Jose Tassignon, MD. Cataract surgery Dr. Schallhorn thinks intraoperative OCT is useful in phaco cases when there are corneal scars or otherwise poor visibility. "[A]nytime I am having difficulty with visualization, I turn on the OCT," she said. "The OCT wavelength is longer than visible light and can penetrate scars better. I have used it to check for capsular integrity and to help my capsulorhexis when I am having difficulty seeing the flap. If you are a divide-and-conquer surgeon, you can also use OCT to check the thickness of the remaining lens." Dr. Tassignon also thinks intraoperative OCT is "of great help" in cataract surgery, for which it is her "main indication." "In adult cataract, it helps to understand the relationship between the posterior capsule and the anteri- or hyaloid and explains the 'floppy capsule,' a condition due to the detachment of the anterior hyaloid from the posterior capsule, also called AVD [anterior vitreous detachment]," she said. "It is probably the most important cause of posterior capsule tear. In pediatric cataract it allowed me to describe a new type of congenital cataract based on a dysgenesis of the anterior interface." 1,2 Intraoperative OCT in practice At a glance • Intraoperative OCT is helpful in cataract surgery cases that have poor visibility, and it provides useful information on the relationship between the posterior capsule and anterior hyaloid. • It is useful in all forms of corneal surgery, elucidating the layers of the cornea, iden- tifying any residual fluid in the donor-recipient interface, and helping orient donor tissue. • Retina cases benefit from in- traoperative OCT's delineation of the layers of the retina, the identification of pathologies such as epiretinal membranes and cystoid macular edema, and real-time assessment of traction during maneuvers such as membrane peeling. continued on page 64 Though primarily a vitreoretinal surgeon, Dr. Findl has had a prototype OCT system as far back as 2011 and has conducted various trials demonstrating the technology's potential for use in cataract and corneal surgery. For in- stance, he has used intraoperative OCT to study the movements of nuclear fragments during emulsification. They observed tiny fragments making pinpoint contact with the central endo- thelium, resulting in endothelial cell loss, even when the view through the microscope showed an apparently perfect surgery. Dr. Findl has also been studying the technology's potential to improve refractive outcomes by refining IOL power calculations. As he described in his 2018 ASCRS Binkhorst Lecture, "The Challenge of Choosing the Right IOL Power," intraoperative OCT can be used to measure the post-cataract removal position of the capsule relative to the corneal apex, which is a good predictor of the IOL position after surgery. This, he said, would be useful for unusually short or long eyes, which can result in refractive surprises. Intraoperative swept-source OCT of the anterior segment depicting the empty capsule bag after I/A and the anterior hyaloid interface Source: Oliver Findl, MD

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