Intraoperative OCT for retinal surgeons

Intraoperative OCT provides retinal surgeons with a valuable tool to guide their instruments and also assess the quality of their work before exiting the eye, said Ramin Tayadoni MD, Lariboisiere Hospital, Paris University, Paris, France . “The benefit of intraoperative OCT for research was obvious from the beginning, but last year I had a question mark about its benefit in clinical practice. This year I delete the question mark. After long-term use, it seems that it is truly useful,” according to Dr Tayadoni. He noted that intraoperative OCT provides, in real time, the same information as pre- or postoperative OCT, such as retinal thickness, the distinction between the layers of the retina, and the presence of openings in the layers. It also provides dynamic information, such as the amount of traction induced during surgery. For example, he noted that in eyes with epiretinal membranes, the most common indication for vitreoretinal surgery, intraoperative OCT makes it easy to see the traction on the retina during membrane peeling and check to see that it returns to its original shape afterwards. Moreover, intraoperative OCT also enables the surgeon to determine whether or not the epiretinal membrane peeling has been complete and whether repeat staining with triamcinolone will be necessary. Similarly when performing inner limiting membrane peeling for vitreomacular traction or macular holes, the surgeon can view the response of the hole to the release of tractional forces and also whether the peeling is complete. “With intraoperative OCT you have your postoperative OCT right away. Therefore if you can eliminate doubt regarding whether you or not have peeled the epiretinal membrane or inner limiting membrane perfectly without using the stain or the dye. Most of the time the intraoperative OCT will do the job,” Dr Tayadoni said. ADVANTAGES IN HIGHLY MYOPIC EYES Dr Tayadoni noted that a study he and his associates conducted showed that the capacity of pre- and post-operative OCT to provide a better determination of macular holes than preoperative fundus examination also extends to the intraoperative stage, with potential for clinical benefit. The investigators performed a retrospective observational analysis of 22 consecutive highly myopic eyes with conditions involving vitreomacular traction, namely myopic foveoschisis, epiretinal membrane and macular holes. When performing the procedures they used RESCAN 700 (Zeiss) Intraoperative OCT system, which integrates spectral domain OCT (SD OCT) into a surgical microscope allowing both direct en face and cross-sectional visualisation of the macular region. They found that the benefits in these eyes were more of qualitative than quantitative nature. Dr Tayadoni noted that quantitative assessment of retinal changes following surgery in terms of central macular thickness in eyes that underwent epiretinal membrane peeling, size of the macular hole, central macular thickness or the foveal detachment base diameter. Qualitative analysis on the other hand showed that two eyes had macular holes that only became detectable with intraoperative OCT. In one case with macular foveoschisis they found that peeling had caused a macular hole. They also found a retinal defect in an eye that underwent epiretinal membrane peeling. How the information should be used is still not clear. It might conceivably lead to improvements in technique that will reduce the complication. In addition, the surgeon might want to consider whether to use a gas tamponade or, in the case of a small hole, watchful waiting. Intraoperative OCT also provides visualisation of the optic nerve, allowing the surgeon to see whether the hyaloid remains attached to it without further staining following treatment for macular holes or foveoschisis, he added. “In our department we don't like to do myopic cases without having this intraoperative OCT device in the operating room. It gives you the post-op OCT intraoperatively, and that reassurance is important because it avoids complementary manoeuvres and their potential complications,” Dr Tayadoni said.