Hindawi Journal of Ophthalmology Volume 2020, Article ID 1497089, 10 pages https://doi.org/10.1155/2020/1497089 Research Article Intraoperative Optical Coherence Tomography Imaging in Corneal Surgery: A Literature Review and Proposal of Novel Applications Hiroshi Eguchi ,1 Fumika Hotta,1 Shunji Kusaka,1 and Yoshikazu Shimomura2 1Department of Ophthalmology, Kindai University, Faculty of Medicine, 377-2 Ohnohigashi, Osakasayama, Osaka 589-8511, Japan 2Department of Ophthalmology, Fuchu Eye Center, 1-10-17 Hiko-cho, Izumi, Osaka 594-0076, Japan Correspondence should be addressed to Hiroshi Eguchi; [email protected] Received 26 June 2020; Revised 12 August 2020; Accepted 21 August 2020; Published 11 September 2020 Academic Editor: Sang Beom Han Copyright © 2020 Hiroshi Eguchi et al. &is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Intraoperative optical coherence tomography (iOCT) is widely used in ophthalmic surgeries for cross-sectional imaging of ocular tissues. &e greatest advantage of iOCTis its adjunct diagnostic efficacy, which facilitates to decision-making during surgery. Since the development of microscopic-integrated iOCT (MIOCT), it has been widely used mainly for vitreoretinal and anterior segment surgeries. In corneal transplantation, MIOCT allows surgeons to visualise structure underneath the turbid and distorted cornea, which are impossible to visualise with a usual microscope. Real-time visualisation of hard-to-see area reduces the operation time and leads to favorable surgical outcomes. &e use of MIOCT is advantageous for a variety of corneal surgical procedures. Here, we have reviewed articles focusing on the utility of iOCT and MIOCTin penetrating keratoplasty, deep anterior lamellar keratoplasty, Descemet stripping automated endothelial keratoplasty, and Descemet membrane endothelial keratoplasty. &e applications of MIOCT to corneal surgery in terms of surgical education for trainees, emergency surgery, and novel surgery are also discussed, with our cases performed using RESCAN® 700. 1. Introduction supine position [2–4]. However, handheld OCTs have limited use in the operation theatre since surgeons need to Intraoperative optical coherence tomography (iOCT) is an discontinue surgical manoeuvres when they obtain OCT imaging modality capable of showing real-time OCT images images or require another medical staff for obtaining the of the ocular tissue. &is system confers advantages for both image using this device, which translates to the OCT images surgeon and the medical staff in the operating theatre during not being truly “real time.” Although no article has reported surgery. Although iOCT is now widely adopted to many the occurrence of intraoperative infections caused by ophthalmic surgeries for intraoperative cross-sectional im- handheld OCT, its use may increase the risk of intra- aging of the ocular tissues, there were some hurdles which operative infection since it entails bringing nonsterile ma- conventional OCT modality must overcome before it is chine from outside of the operation theatre. Involuntary applied in the operating theatre [1]. &e first OCT machines hand movement while using the handheld device also causes were desktop, stationary, and expensive, since they were artifacts, which leads to lower quality of the acquired images initially designed for seated patients in outpatient clinic. [1]. Subsequently, Ray et al. [5] created their own mount for &us, relocating them to the operation theatre for intra- attaching a handheld OCT to the microscope, which allowed operative use was not practical. &ereafter, lightweight the surgeon or assistant to move the device above the pa- handheld OCTs were introduced, making it possible to bring tient’s eye using the microscope foot pedal to ensure the OCT machine into the operation theatre for patients in maintenance of sterility, improve image quality and 2 Journal of Ophthalmology reproducibility, and reduce image capture time. Similarly, For the same reason as mentioned above, there could be Ehlers et al. [6, 7] fastened a handheld probe to the surgical value in the use of MIOCT in PK for educational purpose, microscope to provide increased stability of the probe and especially for the verification of needle depth during su- successfully obtained high quality iOCT images during turing. Ideally, when suturing the graft to the host cornea, vitreoretinal surgery. these structures’ representative Descemet membranes Ehlers et al. were the first to demonstrate a microscope- (DMs) should be at the same height. If they were sutured at integrated iOCT research system, which utilised a spectral the different height, the grafted cornea may dissociate when domain OCT device attached in the space between the the stitches are removed in the future. &erefore, the needle surgeon’s eyepiece and microscope objective in a com- should be passed through a relatively deep corneal stroma, mercial surgical microscope [7, 8]. In recent years, OCT keeping the DMs of both host and graft cornea in mind. probes have been integrated into the microscope as com- However, if the cornea is cloudy, it is not possible to de- mercially available products to enable true “real time” im- termine the depth at where the needle is located using a aging of ocular tissues during the surgery, which was termed typical microscope. If the host and graft were lifted with microscopic-integrated iOCT (MIOCT) [9]. &e greatest forceps so that these cross-sections could be visualised, the advantage of iOCT is its adjunct diagnostic efficacy, which depth of the needle penetration into the cornea can be facilitates decision-making during surgery [6, 9, 10]. Its determined. However, such manoeuvre is impossible and utility has been further enhanced with the advent of MIOCT, undesirable in many cases. &erefore, the depth of the passed which allows the capture of cross-sectional images both on needle is usually estimated using the surgeon’s hand. the microscope barrel and head-up monitor [10] without the Two studies have reported visualisation of the pene- need to discontinue surgical manoeuvre. tration depth of the syringe needle by iOCT in human [33] iOCT was initially developed for anterior segment sur- and porcine cornea [41], but no reports of iOCT confir- gery [11]. &ereafter, it has been applied to vitreoretinal mation of suture needle depth in the human corneal suturing surgeries, with numerous articles on such applications being in PK has yet been published. In the PK case presented in this published. &ese include its use for macular hole [5, 12, 13], study, confirmation of the position of the needle passing epiretinal membrane [5, 14–16], retinal detachment through the cornea was possible through the use of MIOCT. [6, 17–19], and vitreomacular traction [15, 20, 21], among If the needle depth was found to be shallow, determining others [22–27]. Subsequently, its application has been ex- whether the thread should be rethreaded was made by the panded to include glaucoma surgery [28–31] and corneal use of MIOCT and determining if the needle has uninten- transplantation [7, 9, 32–55]. To our knowledge, three tionally penetrated through the host or graft cornea systems are currently commercially available in worldwide: (Figure 1(a)). &e needle is then rethreaded accordingly, and Rescan® 700 (Carl Zeiss Meditec, Germany), OPMedT the host and the graft are adjusted to the appropriate DM (OPMedT, Germany), and Bioptigen/Leica EnFocus (Leica, height (Figure 1(b)). Even for a skilled corneal surgeon, Germany). In this review, we will focus on the utility of passing the suture needle into the cornea at the appropriate iOCT or MIOCT for corneal surgeries, specifically pene- depth each time is not easy. &erefore, MIOCT would be trating keratoplasty (PK), deep anterior lamellar kerato- useful in training of novice doctors for corneal suturing, plasty (DALK), Descemet stripping automated endothelial especially in terms of verifying needle depth during the keratoplasty (DSAEK), and Descemet membrane endothe- procedure. &is verification may also be useful in emergency lial keratoplasty (DMEK). New applications of MIOCT to corneal suturing in cases of corneal rupture and corneal both corneal surgery and in surgical education by intro- perforation. ducing treated cases using Rescan® 700 will be discussed. A report on the application of MIOCT to the latest corneal 3. Deep Anterior Lamellar Keratoplasty (DALK) surgery will also be introduced. In DALK, surgeons always need to assess the thickness of 2. Penetrating Keratoplasty (PK) residual corneal stroma carefully during stromal excision. Even though it may appear that a significant amount of In PK, structures on the underside of the cornea, which are cornea has been removed when viewed from above under a distorted at the host-graft interface, are hard to identify. If the typical microscope, MIOCT often reveals that more cornea structure in the anterior chamber underneath a severe pe- remains than expected when the cross section is examined ripheral corneal scar has changed during surgery, it is also by MIOCT. Ehlers et al. reported in two articles that iOCT difficult to detect the alteration using a typical microscope. facilitated changes in dissection depth in 38–56% of cases During corneal suturing, after trephination of the host cornea, [7, 9]. &e use of air or ophthalmic viscoelastic bubbles iris incarceration