The idea of integrating optical coherence tomography (OCT) into surgery arose during the late 2000s, when surgeons recognized the potential to visualize real-time tissue and surgical interfaces.1 Intraoperative optical coherence tomography (iOCT) thus emerged as a significant innovation in vitreoretinal surgery, transforming how retina specialists visualize and address retinal conditions. Its intraoperative adaptation allows for real-time feedback during surgery, enabling precise assessment of microstructural changes and verification of surgical outcomes.
Since 2010, the technology’s evolution involved adapting existing OCT systems for the operating room, including microscope-mounted (mi-iOCT) and handheld design versions. First described by Tao et al, iOCT has since become a valuable tool for the retina specialist seeking to detect changes and make real-time patient management decisions.2
In the retina community, pars plana vitrectomy (PPV) continues to be one of the most performed surgeries for the management of vitreoretinal disorders, including usage in lens dislocation surgery, epiretinal membrane (ERM), macular hole (MH), and retinal detachment repair (Figure 1). To quantify iOCT’s efficacy with PPV, early efforts, including the PIONEER and DISCOVER trials, were conducted to assess the impact iOCT had on surgeons’ decision-making in the operating room.3,4 These landmark studies demonstrated its feasibility and utility, sparking advancements in integration and ergonomics. iOCT was found to be valuable in up to 50% of cases, influencing intraoperative choices significantly.4 By the mid-2010s, major imaging companies such as Zeiss, Leica, and Haag Streit had developed integrated iOCT solutions to offer enhanced resolution and usability.5 Current imaging systems have platforms tailored to support intraoperative settings, incorporating features such as enhanced eye tracking and compact designs for efficient use. Herein we review the
latest updates in the literature on the clinical usage and application of iOCT in various vitreoretinal diseases.
Figure 1. This intraoperative OCT (iOCT) image, taken with a Leica EnFocus device, shows a dislocated intraocular lens (IOL) in the vitreous cavity. The dislocated IOL is being safely maneuvered off the retina with microforceps. Image courtesy Sidney A. Schechet, MD.
Epiretinal Membrane
iOCT can be valuable during ERM surgery, particularly for the severe, extensive, and/or atypical types where the membrane peel may be more complex. iOCT can be used to find better areas to initiate peeling that are easier to access, aid in visualizing surgical planes (between ERM, ILM, and neurosensory retina, for example), and identify any remaining subtle membranes and traction that still need to be peeled. A retrospective case-control study by Tuifua et al compared clinical outcomes between patients undergoing iOCT-guided PPV for ERM removal and those undergoing conventional PPV with mandatory internal limiting membrane (ILM) peeling.6 When the 2 groups were compared over 1 year postoperatively, there were no statistically significant differences in BCVA outcomes, as both groups experienced similar significant decrease in central subfield thickness (CST). Additionally, both groups did not have visually significant ERM recurrences needing repeat PPV.6
This study demonstrated that iOCT-guided ERM removal without ILM peeling and indocyanine green (ICG) staining achieved comparable visual and anatomic outcomes to conventional ICG-assisted ILM peeling, highlighting the potential of iOCT to offer a less invasive, alternative surgical approach without compromising outcomes.
Macular Hole
iOCT use has been described in MH surgery to study ILM peeling dynamics and retinal architectural changes. iOCT in complex MH surgeries has also been described in the literature, including the use of an amniotic membrane plug and peripheral autologous retinal transplants.7,8 To assess the utility of iOCT in MH surgery, a systematic review was conducted in 2022 by Confalonieri et al, who observed that iOCT provides real-time guidance and feedback in response to various advanced surgical maneuvers, which can confirm intraoperative full-thickness macular hole (FTMH) closure to reduce need for extended postoperative positioning and assist in detecting residual ILM fragments that could influence visual recovery and anatomic outcomes.9
For example, using iOCT to guide techniques like the inverted ILM flap can help vitreoretinal surgeons position flaps correctly, minimizing complications and offering a less traumatic approach while manipulating retinal tissue. iOCT is also useful in identifying key structures during FTMH surgery. For example, using iOCT, Kumar et al identified the “hole-door” sign, named after the appearance of vertical pillars of tissue seen at the edges of a macular hole projecting into the vitreous cavity after ILM peel.10 This sign became a novel intraoperative finding that is associated with a high prediction of postoperative type-1 closure of macular hole. iOCT can also assist the precision of various surgical techniques, such as perfecting the placement and positioning of amniotic membrane or autologous retinal transplants within macular holes, retinal laser, and more (Figures 2 and 3).10,11
Figure 2. Still image from an iOCT scan showing the placement of an autologous retinal transplant over a large macular hole that was previously repaired but reoccurred several years postoperatively. Image courtesy Sidney A. Schechet, MD.
Vitreomacular Traction
iOCT is valuable when operating during vitreomacular traction (VMT) cases. In a retrospective case series of 12 eyes undergoing PPV for VMT using iOCT, Ehlers et al reported that in 42% of cases, iOCT findings led to modifications in the surgical approach, including additional steps such as ILM peeling or gas tamponade, to address newly identified issues such as occult FTMH formation or residual traction.12 iOCT was able to reveal significant changes particularly in the outer retina, such as increased subretinal hyporeflectivtivity and expansion of the distance between the RPE and photoreceptor layers following surgical release of VMT.
In another post hoc analysis of the DISCOVER trial, Huang et al examined the outcomes of iOCT-assisted surgery in 43 eyes with VMT undergoing PPV. iOCT provided critical information in 55.8% of cases and influenced surgical decisions in almost 20% of cases.13
Figure 3. An iOCT scan image used in the same macular hole case demonstrating live laser photocoagulation (A) and resulting laser burns (B) of the retina during repair of a subsequent retinal detachment with proliferative vitreoretinopathy. Image courtesy Sidney A. Schechet, MD.
Retinal Detachment
iOCT proved beneficial especially in complex retinal detachment (RD) cases by assisting in surgical decision-making. In a post hoc analysis of the DISCOVER trial, Abraham et al compared iOCT’s utility and impact on surgical and visual outcomes for uncomplicated primary RD vs complex RD cases.14 In 36% of cases, iOCT was found to provide valuable feedback, and in 12% of cases, iOCT directly influenced surgical decision-making. Complex RD cases were found to benefit more from iOCT, with 50% of complex cases receiving useful feedback compared to 22% of primary cases.
Furthermore, iOCT has been useful for scleral buckle placement in rhegmatogenous retinal detachment (RRD). Sotani et al reported 12 cases of patients who underwent scleral buckling with real-time iOCT, highlighting 5 cases where initial placement needed corrections and that following these adjustments, the scleral buckle surgery resulted in 100% initial anatomic success without significant complications. These cases particularly highlight the ability of iOCT to precisely guide scleral buckle placement to improve outcomes for RRD repair and prevent the need for subsequent repeat or correcting surgeries.15
Multidisciplinary Application
iOCT’s role is expanding across different subspecialties within ophthalmology, offering wider access to care across various ocular conditions. For example, in pediatrics, handheld iOCT can be used for exams under anesthesia for patients with retinopathy of prematurity (ROP), albinism, and nonaccidental trauma.16 iOCT can also provide imaging guidance for critical surgical maneuvers, such as the removal of membranes in complex ROP detachments.
Additionally, iOCT is becoming more widely used in glaucoma surgery in the context of both traditional filtering surgeries and minimally invasive glaucoma surgery (MIGS) procedures.17 iOCT’s ability to improve anterior-segment visualization and facilitate precise surgical maneuvers in challenging anatomic areas like the angle, subconjunctival space, and suprachoroidal space has led to various applications of iOCT in trabeculectomy, stent or drainage device implants, bleb management, and canaloplasty.18
In uveitis, iOCT can provide real-time feedback on the integrity of retinal layers to help various surgical procedures such as membrane peeling, biopsies, and device implants. Reports have described that iOCT can be useful in up to 81% of cases of chorioretinal biopsies while guiding biopsy site selection.19 iOCT can also determine the success of Retisert (Bausch + Lomb) fluocinolone acetonide implant placements in up to 85% of cases, confirming the integrity of scleral wound closure.20 The adaptability of iOCT in various ophthalmic situations highlights its increasing significance in the ophthalmology community.
Challenges and Future Directions
With the potential benefits that iOCT may bring to ophthalmology, associated challenges remain. One roadblock is the inherent incompatibility of iOCT technology across the various brands and models of surgical microscopes.
Other challenges associated with iOCT include efficiency and sterility of the operative field, variance in image quality due to movement, and issues with visualizing surgical instruments when performing scans. For the development of surgical instruments compatible with iOCT, Ehlers et al describe semitransparent rigid plastic material used to develop a few surgical instruments.21 For validation, iOCT imaging of these instruments showed good visualization of each instrument as well as their tissue interaction. Production of iOCT-compatible instruments could further improve the efficacy of iOCT usage by reducing the need for the “stop and scan” method.
Given that iOCT is still emerging, there are potential future developments in the works to improve the technology and further integrate it into regular practice. One example is the use of 4-dimensional technology, using volume through time, to provide further information on surgical techniques and anatomy.22 Another example is the development of an augmented reality headset (Beyeonics One; Beyeonics) that could be integrated with iOCT to provide live information in a heads-up display format.23 In that regard, robotic retinal surgery is another development that is gaining traction. Cereda et al used an integrated iOCT in conjunction with a robotic surgical system (Preceyes Surgical System; Preceyes BV) to study the feasibility of iOCT in robotic vitreoretinal surgery; all but 1 surgical task was reliably completed.24 As iOCT becomes increasingly integrated into these exciting surgical advancements, its use is expected to grow, optimizing workflows, enhancing surgical precision, and ultimately improving patient outcomes.
Conclusion
Intraoperative OCT is an evolving and transformative tool in vitreoretinal surgery, offering real-time feedback that enhances precision and provides novel insights into retinal pathology to guide therapeutic interventions. Despite its potential to improve surgical decisions and clinical outcomes, iOCT remains underutilized by the retina community. With promising clinical trials demonstrating its benefits, we look forward to further exploration of iOCT applications, particularly alongside advancements in surgical platforms and microscopes. As iOCT becomes more integrated and accessible, its role in the operating room will continue to grow, shaping the future of vitreoretinal surgery. RP
References
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