Optical Coherence Tomography for Retinal Surgery: Perioperative Analysis to Real-Time Four-Dimensional Image-Guided Surgery

Abstract

Magnification of the surgical field using the operating microscope facilitated profound innovations in retinal surgery in the 1970s, such as pars plana vitrectomy. Although surgical instrumentation and illumination techniques are continually developing, the operating microscope for vitreoretinal procedures has remained essentially unchanged and currently limits the surgeon's depth perception and assessment of subtle microanatomy. Optical coherence tomography (OCT) has revolutionized clinical management of retinal pathology, and its introduction into the operating suite may have a similar impact on surgical visualization and treatment. In this article, we review the evolution of OCT for retinal surgery, from perioperative analysis to live volumetric (four-dimensional, 4D) image-guided surgery. We begin by briefly addressing the benefits and limitations of the operating microscope, the progression of OCT technology, and OCT applications in clinical/perioperative retinal imaging. Next, we review intraoperative OCT (iOCT) applications using handheld probes during surgical pauses, two-dimensional (2D) microscope-integrated OCT (MIOCT) of live surgery, and volumetric MIOCT of live surgery. The iOCT discussion focuses on technological advancements, applications during human retinal surgery, translational difficulties and limitations, and future directions.

Figure 1

Handheld OCT (HHOCT) imaging during surgical pauses. (A) The surgeon holds the probe over the patient's eye and manually aligns the scan to the site of interest. Intraoperative HHOCT imaging requires displacement of the surgical microscope. (B) Intraoperative HHOCT before (B1) and after (B2) epiretinal membrane (ERM) peeling. Note the multiple ERM attachment points (white arrows) in (B1) and decreased retinal traction (white arrows) in (B2) with normalization of the retinal contour. (C) Preoperative (C1) and intraoperative HHOCT imaging immediately after internal limiting membrane (ILM) peeling (C2) in macular hole surgery. The postpeeling scan (C2) shows the elevated appearance of the hole edge and smaller base diameter, suggesting reduced traction. Residual ILM (white arrow) is also visible in (C2) as distinct hyperreflectivity along the retinal surface. Figures reprinted with permission from Dayani PN, Maldonado R, Farsiu S, Toth CA. Intraoperative use of handheld spectral domain optical coherence tomography imaging in macular surgery. Retina. 2009;29:1457–1468. © 2009 The Ophthalmic Communications Society, Inc.⁷⁰

Figure 2

Live 2D microscope-integrated OCT (MIOCT) imaging of human retinal surgery. (A) System in use during human retinal surgery. MIOCT allows concurrent visualization of surgery with the operating microscope and OCT. (B) Imaging in a human patient undergoing surgery for macular hole repair. The preincision image (B1) depicts the macular hole and confirms the preoperative diagnosis. Imaging following internal limiting membrane peeling (ILM) (B2) suggests a more relaxed retinal contour, shows the location of residual ILM (asterisks), and reveals intraretinal hemorrhage (double arrow), small intraretinal cystoid spaces (arrowheads), and subretinal fluid (arrow). (C) Excerpts of a real-time B-scan recording of retinal brushing with a diamond-dusted retinal scraper during epiretinal membrane removal. The large images were denoised in postprocessing; the smaller insets are the corresponding non-postprocessed images viewable intraoperatively. (A, B) Reprinted with permission from Hahn P, Migacz J, O'Donnell R, et al. Preclinical evaluation and intraoperative human retinal imaging with a high-resolution microscope-integrated spectral domain optical coherence tomography device. Retina. 2013;33:1328–1337. © 2013 by Ophthalmic Communications Society, Inc.⁹¹; (C) reprinted with permission from Hahn P, Carrasco-Zevallos O, Cunefare D, et al. Intrasurgical human retinal imaging with manual instrument tracking using a microscope-integrated spectral-domain optical coherence tomography device. Trans Vis Sci Tech. 2015;4:1–9. © 2015 The Association for Research in Vision and Ophthalmology, Inc.⁹⁴

Figure 3

Live 2D MIOCT imaging of human retinal surgery with the commercially available RESCAN 700 and a Cirrus HD-OCT system adapted to an operating microscope. (A) Frame captured with the camera that records the surgeon's view through the operating microscope. The orthogonal arrows correspond to the B-scan locations. (B) Horizontal (B1) and vertical (B2) B-scans acquired with the RESCAN 700 during inner limiting membrane (ILM) peeling. The membrane edge (white arrowheads) is clearly visible in the B-scans along with “shadowing” (yellow arrowheads) from the intraocular forceps. (C) B-scan (C1) and volume (C2) acquired intraoperatively before epiretinal membrane (ERM) peeling with the reconfigured Cirrus HD-OCT system. (D) B-scan (D1) and volume (D2) acquired after ERM peeling. The volumes required intensive postprocessing to render and were visualized postoperatively. The prepeeling volumes depict ERM and puckering of the retina, while the postpeeling volumes show a small residual part of ERM. (A, B) Reprinted with permission from Ehlers JP, Goshe J, Dupps WJ, et al. Determination of feasibility and utility of microscope-integrated optical coherence tomography during ophthalmic surgery: the DISCOVER Study RESCAN Results. JAMA Ophthalmol. 2015;133:1124–1132. © 2015 American Medical Association. All rights reserved.⁹⁵; (C, D) reprinted with permission from Falkner-Radler CI, Glittenberg C, Gabriel M, Binder S. Intrasurgical microscope-integrated spectral domain optical coherence tomography-assisted membrane peeling. Retina. 2015;35:2100–2106. © 2015 by Ophthalmic Communications Society, Inc.

Figure 4

4D MIOCT imaging during live human retinal surgery to remove an epiretinal membrane associated with a partial-thickness lamellar hole. All volumes and B-scans were viewable intraoperatively by the surgeon with the stereo heads-up display. (A) Volume (A1) and corresponding B-scan (A2) of retinal brushing with a membrane scraper (red asterisk) during inner limiting membrane (ILM) peeling (yellow arrow) (see Supplementary Movie S1). (B) Volume (B1) and corresponding B-scan (B2) of ILM peeling with intraocular forceps (blue asterisk) (see Supplementary Movie S2). The white rectangle on the volumes denotes the B-scan location. Instrument–ILM interaction, deformation of the lamellar hole, and underlying intraretinal cystoid spaces are shown in the images. (C) Prepeeling surgical visualization with a frame from the surgical camera recording (C1), B-scan (C2), and volume (C3). (D) Postpeeling visualization of the same region. Compared to the prepeeling volume, the postpeeling volume shows decreased lamellar hole size (green) while the B-scan confirms removal of ILM adjacent to the hole. Note the enhanced visualization of choroid (compared to SD-MIOCT at ∼850 nm) due to the use of longer wavelengths for 4D MIOCT imaging. Scale bars: 1 mm.

Figure 5

4D MIOCT volumetric recording of retinal brushing with a membrane scraper during human retinal surgery for removal of epiretinal membrane (ERM). The images were viewable intraoperatively by the surgeon with the stereo heads-up display. Excerpts from the time series (A1–A4) are shown in volumes (top row) and corresponding B-scans (bottom row). The white rectangle on the volumes denotes the B-scan location. Both the membrane scraper (red asterisk) and ERM (yellow arrow) are clearly visualized in the volumes and B-scans. The volumes show retinal contour deformation during instrument contact and three-dimensional ERM structural alterations during and after brushing. Increased retinal surface tension is particularly prominent in (A2) and (A3). Scale bars: 1 mm.