Clinical Experience With the First Commercially Available Intraoperative Optical Coherence Tomography System

The State of Intraoperative OCT in Vitreoretinal Surgery: Recent Advances and Future Challenges

Since its first introduction more than 30 years ago, optical coherence tomography (OCT) has revolutionized ophthalmology practice, providing a non-invasive in vivo cross-sectional view of the structures of the eye. Mostly employed in the clinical setting due to its tabletop configuration requiring an upright patient positioning, the recent advent of microscope-integrated systems now allows ophthalmologists to perform real-time intraoperative OCT (iOCT) during vitreoretinal surgical procedures. Numerous studies described various applications of this tool, such as offering surgeons feedback on tissue-instrument interactions in membrane peeling, providing structural images in macular hole repair, and showing residual subretinal fluid or perfluorocarbon in retinal detachment surgery. This narrative review aims at describing the state of the art of iOCT in vitreoretinal procedures, highlighting its modern role and applications in posterior segment surgery, its current limitations, and the future perspectives that may improve the widespread adoption of this technology.

[Intraoperative optical coherence tomography in vitreoretinal surgery]

This article reviews literature on the use of intraoperative optical coherence tomography (iOCT) in vitreoretinal surgery, describes the historical aspects of the development of this technology from portable devices to optical coherence tomographs integrated into the surgical microscope, considers the advantages, limitations and disadvantages of this technology, which are now becoming obvious due to the accumulated experience. The review also explores the prospects for the development of iOCT and possible ways to solve its problems. In addition, the review presents and systematizes clinical findings that can be revealed with iOCT in such diseases as rhegmatogenous retinal detachment, complications of proliferative diabetic retinopathy, macular pathology, etc.

Posterior Segment Optical Coherence Tomography in Uncooperative Paediatric Patients Using Exo-Illumination and Microscope-Integrated Optical Coherence Tomography

BACKGROUND AND OBJECTIVE

To describe a non-invasive technique for the acquisition of retinal optical coherence tomography (OCT) scans in paediatric patients undergoing examination under general anaesthesia (EUA) using microscope-integrated OCT (MIOCT).

STUDY DESIGN

Prospective observational study Methods and Material: The study included 10 paediatric patients undergoing EUA for posterior segment pathology. These patients underwent OCT using MIOCT. No sclerotomy was made during imaging. The fundus was externally illuminated with a 25 gauge endoilluminator probe placed at the limbus and directed towards the posterior pole to aid in image acquisition by MIOCT (exo-illumination). Imaging for all patients was done by two trained vitreoretinal surgeons independently. Acquisition time was recorded for each surgeon. Interobserver variability in acquisition time and image quality was assessed to estimate the reliability of the novel imaging technique.

RESULTS

In nine cases (90%), MIOCT successfully imaged the posterior segment pathology while in one case (10%) of X-linked retinoschisis, it failed to detect an inner retinal break located anteriorly at the equator. The mean acquisition time for surgeons one and two was 211.75 ± 26.00 and 212.58 ± 23.47 seconds, respectively. There was no significant difference in total image acquisition time between the two surgeons (P = 1.0) and the findings of both surgeons were comparable for structural morphology. 4x4 mm-sized scans provided the best delineation in macular pathology, while a 16x16 mm scan size was best suited for localising the area of interest and post-equatorial pathology.

CONCLUSION

Using this technique acquisition of posterior segment OCT scans can be achieved non-invasively, using exo-illumination and MIOCT in paediatric patients undergoing EUA.

Intraoperative Optical Coherence Tomography in Idiopathic Macular Epiretinal Membrane Surgery

Objective

To evaluate the feasibility and practicability of intraoperative optical coherence tomography (IOCT) in the surgery of idiopathic macular epiretinal membrane (IMM) without internal limiting membrane staining in all patients.

Methods

Patients were selected from July 2018 to June 2020, and 32 patients (32 eyes) with IMM were operated with the use of IOCT. All patients underwent standard 23g vitrectomy. The internal limiting membrane was peeled off if there were obvious retinal folds. Intraoperative and postoperative complications, macular microstructural changes, and integrity of the detached membranes were recorded. The preoperative and postoperative best corrected visual acuity were compared.

Results

The macular epiretinal membrane was completely removed in 75% (24 eyes) patients without internal limiting membrane staining, and in 15.6% (5 eyes) patients with combined internal limiting membrane stripping. The "starting point" of macular epiretinal membrane stripping was found in 75% (24 eyes), and the time required to find the best starting point ranged from 28s to 140s (mean 66 ± 15s). At 3 months after operation, 96.8% of the patients had stable or improved BCVA (p < 0.05). The central macular thickness of the affected eyes decreased significantly at 1 and 3 months after operation (p < 0.05).

Conclusion

IOCT can significantly reduce the use of internal limiting membrane staining in idiopathic macular epiretinal membrane surgery, and it is safe, feasible and practical in idiopathic macular epiretinal membrane surgery without internal limiting membrane staining in all patients.

Intraoperative Optical Coherence Tomography Guided Ocular Surgeries: Critical Analysis of Clinical Role and Future Perspectives

Intraoperative imaging of ocular tissues for diagnostic and therapeutic applications has gained immense admiration in recent years. The real time cross-sectional imaging, as well as three and four dimensional reconstruction abilities of intraoperative optical coherence tomography (iOCT), has enhanced our knowledge on many fronts in surgical maneuvers. In this review, we discuss the iOCT discovered constructive knowledge in the cornea, cataract, refractive, glaucoma, pediatric ocular, and various retinal conditions. The practical utility with decision modifying aspects along the specified ocular tissues and with respect to specific ocular entities have been narrated. Moreover, limitations and future directions have also been emphasized to make ophthalmic care more comprehensive in the future.

What Is the Impact of Intraoperative Microscope-Integrated OCT in Ophthalmic Surgery? Relevant Applications and Outcomes. A Systematic Review

Background: Optical coherence tomography (OCT) has recently been introduced in the operating theatre. The aim of this review is to present the actual role of microscope-integrated optical coherence tomography (MI-OCT) in ophthalmology. Method: A total of 314 studies were identified, following a literature search adhering to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. After full-text evaluation, 81 studies discussing MI-OCT applications in ophthalmology were included. Results: At present, three microscope-integrated optical coherence tomography systems are commercially available. MI-OCT can help anterior and posterior segment surgeons in the decision-making process, providing direct visualization of anatomic planes before and after surgical manoeuvres, assisting in complex cases, and detecting or confirming intraoperative complications. Applications range from corneal transplant to macular surgery, including cataract surgery, glaucoma surgery, paediatric examination, proliferative diabetic retinopathy surgery, and retinal detachment surgery. Conclusion: The use of MI-OCT in ophthalmic surgery is becoming increasingly prevalent and has been applied in almost all procedures. However, there are still limitations to be overcome and the technology involved remains difficult to access and use.

Conventional Microscope-Integrated Intraoperative OCT Versus Digitally Enabled Intraoperative OCT in Vitreoretinal Surgery in the DISCOVER Study

BACKGROUND AND OBJECTIVE

To compare conventional microscope-integrated intraoperative optical coherence tomography (iOCT) and digitally enabled microscope-integrated iOCT in vitreoretinal surgery.

PATIENTS AND METHODS

In this post-hoc analysis of the DISCOVER prospective iOCT study, two surgical groups were compared: (1) conventional iOCT and (2) digitally enabled iOCT. Surgeon questionnaires were collected immediately following surgery.

RESULTS

A total of 187 subjects were included in the study: 91 in the conventional iOCT group and 96 in the digitally enabled iOCT group. There were no differences in surgeon-perceived iOCT utility between the two groups. There was significantly higher surgical field-based visualization of the iOCT datastream in the digitally enabled iOCT group (67.7% vs. 3.3%; P < .0001). Reported significant back discomfort (1.0% vs. 18.7%; P < .0001) and headaches (5.2% vs. 20.9%; P < .002) were lower in the digitally enabled iOCT group.

CONCLUSIONS

Feasibility and utility of iOCT were similar in both groups. Digitally enabled iOCT datastream enabled increased attention on the surgical field during OCT review. [Ophthalmic Surg Lasers Imaging Retina. 2020;51:S37-S43.].

Intraoperative Optical Coherence Tomography Demonstrating Macular Hole Associated With Ruptured Retinal Arterial Macroaneurysm

A 67-year-old female presented with vitreous hemorrhage and sub-internal limited membrane (ILM) hemorrhage in her right eye associated with ruptured retinal arterial macroaneurysm. During pars plana vitrectomy, intraoperative optical coherence tomography aided in the diagnosis of a small macular hole previously obscured by the sub-ILM hemorrhage. Nonexpansile gas was placed followed by postoperative prone positioning, and the hole closed successfully. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:e125-e127.].

Intra-operative optical coherence tomography in glaucoma surgery-a systematic review

The application of the OCT in clinical ophthalmology has expanded significantly since its introduction more than 20 years ago. There has been recent growing interest in the application of intra-operative optical coherence tomography (iOCT). The iOCT's ability to enhance visualisation and depth appreciation has the potential to be further exploited in glaucoma surgery, especially with the emergence of Minimally Invasive Glaucoma Surgery (MIGS)-to facilitate targeted device placement and fine surgical manoeuvres in the angles, the sub-conjunctival layer and the suprachoroidal space. Hence, this study aims to appraise the current literature on the applications of iOCT in glaucoma surgery. A total of 79 studies were identified following a literature search adhering to PRISMA guidelines. After full text evaluation, 10 studies discussing iOCT use in glaucoma surgery were included. Traditional glaucoma filtering procedures reviewed included trabeculectomy surgery, goniosynechiolysis, bleb needling and glaucoma drainage device implantation. MIGS procedures reviewed included canaloplasty, trabecular aspiration, ab-interno trabectome and the XEN45 gel stent. iOCT use in ophthalmic surgery is becoming increasingly prevalent and has already been applied in various surgeries and procedures in the field of glaucoma. With the greater adoption of MIGS, iOCT may further contribute in facilitating surgical techniques and improving outcomes. While iOCT offers many advantages, there are still limitations to be overcome-iOCT technology continues to evolve to optimise imaging quality and user-experience.

Intraoperative Optical Coherence Tomography in Vitreoretinal Surgery

Intraoperative OCT (iOCT) is an emerging modality capable of displaying real-time OCT images to the surgeon during surgery. The use of iOCT during vitreoretinal surgery improves our understanding of the tissue alterations that occur during surgical manipulations, which may impact surgical decision-making. We review the current iOCT modalities and clinical applications of iOCT.

Microscope-Integrated Intraoperative Ultrahigh-Speed Swept-Source Optical Coherence Tomography for Widefield Retinal and Anterior Segment Imaging

BACKGROUND AND OBJECTIVE

To demonstrate the feasibility of retinal and anterior segment intraoperative widefield imaging using an ultrahigh-speed, swept-source optical coherence tomography (SS-OCT) surgical microscope attachment.

PATIENTS AND METHODS

A prototype post-objective SS-OCT using a 1,050-nm wavelength, 400 kHz A-scan rate, vertical cavity surface-emitting laser (VCSEL) light source was integrated to a commercial ophthalmic surgical microscope after the objective. Each widefield OCT data set was acquired in 3 seconds (1,000 × 1,000 A-scans, 12 × 12 mm² for retina and 10 × 10 mm² for anterior segment).

RESULTS

Intraoperative SS-OCT was performed in 20 eyes of 20 patients. In six of seven membrane peels and five of seven rhegmatogenous retinal detachment repair surgeries, widefield retinal imaging enabled evaluation pre- and postoperatively. In all seven cataract cases, anterior imaging evaluated the integrity of the posterior lens capsule.

CONCLUSIONS

Ultrahigh-speed SS-OCT enables widefield intraoperative viewing in the posterior and anterior eye. Widefield imaging visualizes ocular structures and pathology without requiring OCT realignment. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:94-102.].

Intraoperative Optical Coherence Tomography-Guided Membrane Peeling for Surgery of Macular Pucker: Advantages and Limitations

PURPOSE

Epiretinal membranes (ERMs) are a disorder leading to progressive vision loss and metamorphopsia. The gold standard in therapy is vitrectomy with membrane peeling. The aim of this study was to assess whether the use of intraoperative optical coherence tomography (iOCT), which allows tomographic visualization of the membrane during peeling, enables peeling without staining.

METHODS

This prospective study included 30 eyes of 30 patients with idiopathic ERMs scheduled for surgery. Pars plana vitrectomy with iOCT was performed in all cases, whereas staining of ERMs was only performed if needed. Internal limiting membrane (ILM) peeling was performed in case of wrinkled retinal surface after peeling of ERMs.

RESULTS

In 63% (n = 19) eyes the ERM could be peeled successfully without use of staining. Nevertheless, in 89% (n = 17) of patients having had ERM peeling without dye, staining of the ILM was performed afterwards for peeling the ILM. Best corrected visual acuity improved in 80% (n = 24) and remained unchanged in 7% (n = 2) 3 months after surgery. There were no significant differences in postoperative results between patients with and without staining for ERM peeling.

CONCLUSIONS

Use of iOCT helps to complete ERM peeling in a majority of cases without use of a chromovitrectomy dye, but as iOCT fails to visualize the ILM, chromovitrectomy still facilitates macular surgery in a majority of cases.

Use of iOCT in Vitreoretinal Surgery for Dense Vitreous Hemorrhage in a Chinese Population

PURPOSE

To evaluate the feasibility and utility of intraoperative optical coherence tomography (iOCT) during pars plana vitrectomy (PPV) surgery for dense vitreous hemorrhage (VH).

METHODS

A retrospective, consecutive, interventional case series. A total of 68 dense VH patients (71 eyes) were enrolled, and the patients were divided into two groups. The control group (43 eyes) did not receive iOCT and the experimental group (28 eyes) did. All patients with macular structures that could not be assessed by preoperative OCT underwent PPV for dense VH. iOCT images were qualitatively evaluated for retinal abnormalities that might affect intraoperative management. The assessment of iOCT utility was evaluated by the surgeon. Intraoperative membrane peeling, postoperative macular structure, and postoperative visual acuity were compared between the two groups.

RESULTS

There were no significant differences in sex, age, different etiologies of VH, or best corrected visual acuity between the two groups at baseline. In the experimental group, iOCT revealed macular edema (eight eyes, 28.6%), epiretinal membranes (ERM, five eyes, 17.9%), macular atrophy (one eye, 3.6%), lamellar macular hole (one eye, 3.6%), polypoidal choroidal vasculopathy (one eye, 3.6%), and the existence of both macular edema with ERM (one eye, 3.6%). Eight cases showed macular abnormalities on the iOCT images that were inconsistent with the surgeon's judgment without iOCT. iOCT imaging affected the surgical plan for seven of the eight cases. Significantly more iOCT eyes had intraoperative membrane peeling than control eyes (P = 0.01), while significantly fewer iOCT eyes had postoperative ERMs (P = 0.04).

CONCLUSIONS

iOCT during PPV for VH may provide the surgeon with clinically relevant information that influences surgical management. The iOCT group had a higher incidence of ERM peeling intraoperatively and lower incidence of ERM postoperatively compared with the control group.

THE INTEGRATIVE SURGICAL THEATER: Combining Intraoperative Optical Coherence Tomography and 3D Digital Visualization for Vitreoretinal Surgery in the DISCOVER Study

PURPOSE

To evaluate the feasibility of integrating intraoperative optical coherence tomography (OCT) with a digital visualization platform for vitreoretinal surgery.

METHODS

The DISCOVER study is a prospective study examining microscope-integrated intraoperative OCT across multiple prototypes and platforms. For this assessment, a microscope-integrated OCT platform was combined with a three-dimensional (3D) surgical visualization system to allow for digital display of the OCT data stream on the large immersive display. Intraoperative OCT scans were obtained at various surgical milestones that were directly overlaid to the surgical view in a 55-inch passive 3D 4K high-definition display. Surgeon feedback was obtained related to system performance and integration into the surgical procedures through a prespecified surgeon questionnaire.

RESULTS

Seven eyes of seven subjects were identified. Clinical diagnosis included epiretinal membrane (n = 3), macular hole (2), symptomatic vitreous opacity (1), and proliferative vitreoretinopathy (1). Optical coherence tomography images were successfully obtained and displayed on the 4K screen in all cases. Intraoperative OCT images facilitated identification of subtle retinal alterations. Surgeons reported that the 4K screen seemed to provide improved visualization of the OCT data stream compared with the semitransparent ocular view. Surgeons were able to examine the OCT data on the 4K screen without reverting to the external display system of the microscope. The system provided a uniform surgical visualization experience for both the surgeon and the assistant. In addition, the digital platform allowed all surgical personnel to simultaneously view both the OCT and the surgical field. All eyes underwent uneventful vitrectomy without reverting to the conventional microscope. No intraoperative adverse events occurred.

CONCLUSION

Integration of OCT into the digital visualization system may enable unique opportunities for surgeon feedback of intraoperative diagnostics. The overlay of the OCT data onto the 4K monitor seemed to provide excellent visualization of OCT details. Further research is needed to compare the conventional microscope-based approach to the digital 3D screen approach in regards to intraoperative OCT.

The DISCOVER Study 3-Year Results: Feasibility and Usefulness of Microscope-Integrated Intraoperative OCT during Ophthalmic Surgery

PURPOSE

To report the 3-year assessment of feasibility and usefulness of microscope-integrated intraoperative OCT (iOCT) during ophthalmic surgery.

DESIGN

Prospective, consecutive case series.

PARTICIPANTS

Adult participants undergoing incisional ophthalmic surgery with iOCT imaging who consented to be enrolled in the Determination of Feasibility of Intraoperative Spectral-Domain Microscope Combined/Integrated OCT Visualization during En Face Retinal and Ophthalmic Surgery (DISCOVER) study.

METHODS

The DISCOVER study is a single-site, multisurgeon, institutional review board-approved investigational device prospective study. Participants included patients undergoing anterior or posterior segment surgery who underwent iOCT imaging with 1 of 3 prototype microscope-integrated iOCT systems (i.e., Zeiss Rescan 700, Leica EnFocus, or Cole Eye iOCT systems). Clinical characteristics were documented, iOCT was directed by the operating surgeon at predetermined surgical time points, and each surgeon completed a questionnaire after surgery to evaluate the usefulness of iOCT during surgery.

MAIN OUTCOME MEASURES

Feasibility of iOCT based ability to obtain an OCT image during surgery and usefulness of iOCT based on surgeon reporting during surgery.

RESULTS

Eight hundred thirty-seven eyes (244 anterior segment cases and 593 posterior segment cases) were enrolled in the DISCOVER study. Intraoperative OCT demonstrated feasibility with successful image acquisition in 820 eyes (98.0%; 95% confidence interval [CI], 96.8%-98.8%). In 106 anterior segment cases (43.4%; 95% CI, 37.1%-49.9%), the surgeons indicated that the iOCT information impacted their surgical decision making and altered the procedure. In posterior segment procedures, surgeons reported that iOCT enabled altered surgical decision making during the procedure in 173 cases (29.2%; 95% CI, 25.5%-33.0%).

CONCLUSIONS

The DISCOVER iOCT study demonstrated both generalized feasibility and usefulness based on the surgeon-reported impact on surgical decision making. This large-scale study confirmed similar findings from other studies on the potential value and impact of iOCT on ophthalmic surgery.

Real-time corneal segmentation and 3D needle tracking in intrasurgical OCT

Ophthalmic procedures demand precise surgical instrument control in depth, yet standard operating microscopes supply limited depth perception. Current commercial microscope-integrated optical coherence tomography partially meets this need with manually-positioned cross-sectional images that offer qualitative estimates of depth. In this work, we present methods for automatic quantitative depth measurement using real-time, two-surface corneal segmentation and needle tracking in OCT volumes. We then demonstrate these methods for guidance of ex vivo deep anterior lamellar keratoplasty (DALK) needle insertions. Surgeons using the output of these methods improved their ability to reach a target depth, and decreased their incidence of corneal perforations, both with statistical significance. We believe these methods could increase the success rate of DALK and thereby improve patient outcomes.

MACULAR HOLE FORMATION IDENTIFIED WITH INTRAOPERATIVE OCT DURING VITRECTOMY FOR VITREOMACULAR TRACTION SYNDROME

PURPOSE

To report the identification of macular hole formation using intraoperative optical coherence tomography (OCT) during vitrectomy for vitreomacular traction syndrome.

METHODS

A 58-year-old woman with vitreomacular traction syndrome underwent the vitrectomy using the 25-gauge system with scanning the macular area using the integrated and intraoperative OCT (Rescan 700, Zeiss). When posterior vitreous detachment at the fovea was performed using a vitreous cutter, the hyperreflective tissue thought to be the rupture of the internal limiting membrane and the full-thickness macular hole were identified on the horizontal and vertical scans simultaneously in intraoperative OCT.

RESULTS

The procedure was completed after internal limiting membrane peeling and 25% SF6 gas tamponade for closure of macular hole. The closure was confirmed using Swept-Source OCT 1-month after surgery.

CONCLUSION

It is possible to change the surgical approach using the real-time intraoperative OCT because the development of macular hole can be visualized during vitrectomy for vitreomacular traction syndrome.

Utility of microscope-integrated optical coherence tomography (MIOCT) in the treatment of myopic macular hole retinal detachment

Macular hole-associated retinal detachment in high myopia is described as a final stage in progression of myopic traction maculopathy (MTM).^1â€"3 Shimada et al⁴ described the progressive stages of MTM from macular retinoschisis to serous retinal detachment in high myopia. Stage 4 MTM is characterised as disappearance of retinoschisis with progression to retinal detachment due to macular hole formation. It is hypothesised that vitreoschisis and abnormal vitreo-retinal interface create the premacular tangential traction.^{5 6} Intraoperative triamcinolone acetonide is used to visualise the residual posterior vitreous cortex (PVC). We hereby describe the utility of microscope-integrated optical coherence tomography (MIOCT) in assisting complete removal of PVC and internal limiting membrane (ILM) peeling with multilayered inverted ILM flap in the treatment of myopic macular hole retinal detachment. MIOCT helped identify vitreoschisis and confirm the position of ILM flaps over the macular hole intraoperatively.

Microscope-Integrated OCT Feasibility and Utility With the EnFocus System in the DISCOVER Study

BACKGROUND AND OBJECTIVE

To evaluate the feasibility and utility of a novel microscope-integrated intraoperative optical coherence tomography (OCT) system.

PATIENTS AND METHODS

The DISCOVER study is an investigational device study evaluating microscope-integrated intraoperative OCT systems for ophthalmic surgery. This report focuses on subjects imaged with the EnFocus prototype system (Leica Microsystems/Bioptigen, Morrisville, NC). OCT was performed at surgeon-directed milestones. Surgeons completed a questionnaire after each case to evaluate the impact of OCT on intraoperative management.

RESULTS

Fifty eyes underwent imaging with the EnFocus system. Successful imaging was obtained in 46 of 50 eyes (92%). In eight cases (16%), surgical management was changed based on intraoperative OCT findings. In membrane peeling procedures, intraoperative OCT findings were discordant from the surgeon's initial impression in seven of 20 cases (35%).

CONCLUSION

This study demonstrates the feasibility of microscope-integrated intraoperative OCT using the Bioptigen EnFocus system. Intraoperative OCT may provide surgeons with additional information that may influence surgical decision-making. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:216-222.].

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

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.

Review of intraoperative optical coherence tomography: technology and applications [Invited]

During microsurgery, en face imaging of the surgical field through the operating microscope limits the surgeon's depth perception and visualization of instruments and sub-surface anatomy. Surgical procedures outside microsurgery, such as breast tumor resections, may also benefit from visualization of the sub-surface tissue structures. The widespread clinical adoption of optical coherence tomography (OCT) in ophthalmology and its growing prominence in other fields, such as cancer imaging, has motivated the development of intraoperative OCT for real-time tomographic visualization of surgical interventions. This article reviews key technological developments in intraoperative OCT and their applications in human surgery. We focus on handheld OCT probes, microscope-integrated OCT systems, and OCT-guided laser treatment platforms designed for intraoperative use. Moreover, we discuss intraoperative OCT adjuncts and processing techniques currently under development to optimize the surgical feedback derivable from OCT data. Lastly, we survey salient clinical studies of intraoperative OCT for human surgery.

Long-term surgical outcomes of the inverted internal limiting membrane flap technique in highly myopic macular hole retinal detachment

BACKGROUND

Pars plana vitrectomy (PPV) procedures are used for the surgical treatment of macular hole retinal detachment (MHRD) associated with high myopia. Re-detachment of the retina has been reported in MHRD associated with high myopia. Our aim was to evaluate the 1-year outcomes of vitrectomy, performed using an inverted internal limiting membrane (ILM) flap technique with gas tamponade, in five cases of MHRD associated with high myopia.

METHODS

We performed a retrospective review of medical records of five consecutive cases of highly myopic MHRD. The following postoperative data were collected: refractive error, best-corrected visual acuity, intraocular pressure, ophthalmic fundus examination findings, ocular coherence tomography at 1, 3, 6, and 12 months postoperatively; duration of the follow-up period; and intra- and postoperative complications. The primary endpoint of the study was the rate of postoperative retinal reattachment and macular hole (MH) closure. Paired t-tests were conducted to evaluate postoperative changes.

RESULTS

Mean visual acuity improved significantly (P = 0.008), with an improvement of ≥2 lines on LogMAR value gained in three of the five eyes. Retinal reattachment was maintained in all cases, with no cases of MH reopening identified over the mean follow-up period of 20.2 months. No complications were identified in any eye.

CONCLUSIONS

The inverted ILM flap technique and gas tamponade provided primary retinal reattachment and MH closure over the ≥12-month follow-up period.

Clinical utility of intraoperative optical coherence tomography

PURPOSE OF REVIEW

To explore the clinical utility of intraoperative optical coherence tomography (iOCT) for the management of vitreoretinal conditions.

RECENT FINDINGS

The role of iOCT in guiding surgical decision-making and surgical manipulations during vitreoretinal procedures has been evaluated by multiple studies. This imaging modality is emerging as a valuable asset during procedures for vitreoretinal interface disorders, retinal detachments, submacular surgeries and therapeutics, and in pediatric conditions such as retinopathy of prematurity. iOCT allows the surgeon to assess completion of surgical goals and to directly monitor the architectural impact of instrument-tissue interactions that may correlate with eventual prognosis. The technology has gone through numerous iterations with the eventual goal being the development of a user-friendly, efficient, and integrated system that provides surgeons with 'real-time' feedback during ophthalmic surgeries to allow for a comprehensive image-assisted vitreoretinal surgery platform.

SUMMARY

The role of iOCT in ophthalmic surgery has been evolving with the help of ongoing research to define its utility in the operating room and to develop integrative technologies. Advancements in OCT-friendly surgical instrumentation and in integrative capabilities of this technology may help achieve more widespread adoption of this technology in the vitreoretinal surgical theater. Although the evidence appears clear that this technology impacts surgical decision-making, additional research is needed. However, further research is needed to determine the influence of this technology on overall patient outcomes.

Live volumetric (4D) visualization and guidance of in vivo human ophthalmic surgery with intraoperative optical coherence tomography

Minimally-invasive microsurgery has resulted in improved outcomes for patients. However, operating through a microscope limits depth perception and fixes the visual perspective, which result in a steep learning curve to achieve microsurgical proficiency. We introduce a surgical imaging system employing four-dimensional (live volumetric imaging through time) microscope-integrated optical coherence tomography (4D MIOCT) capable of imaging at up to 10 volumes per second to visualize human microsurgery. A custom stereoscopic heads-up display provides real-time interactive volumetric feedback to the surgeon. We report that 4D MIOCT enhanced suturing accuracy and control of instrument positioning in mock surgical trials involving 17 ophthalmic surgeons. Additionally, 4D MIOCT imaging was performed in 48 human eye surgeries and was demonstrated to successfully visualize the pathology of interest in concordance with preoperative diagnosis in 93% of retinal surgeries and the surgical site of interest in 100% of anterior segment surgeries. In vivo 4D MIOCT imaging revealed sub-surface pathologic structures and instrument-induced lesions that were invisible through the operating microscope during standard surgical maneuvers. In select cases, 4D MIOCT guidance was necessary to resolve such lesions and prevent post-operative complications. Our novel surgical visualization platform achieves surgeon-interactive 4D visualization of live surgery which could expand the surgeon’s capabilities.