Sebastian Siebelmann

Intraoperative Optical Coherence Tomography: Ocular Surgery on a Higher Level or Just Nice Pictures?

In recent years, optical coherence tomography (OCT) has developed into one of the most important imaging techniques in ophthalmology. Nonetheless, this technology is still evolving rapidly as recent developments in multimodal swept-source OCT devices and 4-dimensional real-time OCT demonstrate. Another currently developing sector in OCT application is the intraoperative use of OCT technology. Several approaches have been used to transfer OCT into an intraoperative setting, beginning with OCT-compatible positioning of the anesthetized patient1 and handheld OCT devices.2 The latest step in this evolution is the integration of OCT devices into surgical microscopes, allowing for the correlation of the magnified microscope image with the OCT image and for exact positioning systems of OCT and microscope, thus avoiding artifacts. Moreover, the integration of OCT into the surgical microscope and the visualization via the heads-up display facilitates the online monitoring of the surgical procedure without interruption and without the necessity to switch between OCT and microscope, thus reducing surgery times. Currently, to our knowledge, there exist 2 commercially available and US Food and Drug Administration–approved microscope-integrated OCT devices (the RESCAN 700 integrated into the OPMI Lumera 700 from Carl Zeiss Meditec AG and the iOCT from Optomedical Technologies integrated into the HS Hi-R Neo 900A from Haag-Streit Surgical GmBH). In addition, one other device can be used for handheld and microscope-integrated setups, the Envivu C-Class from Bioptigen. According to our own experience, intraoperative OCT is able to deliver new information during several surgical procedures, especially in the anterior segment and especially in eyes with opaque media. Examples of potentially useful indications for intraoperative OCT include anterior lamellar corneal grafting (deep anterior lamellar keratoplasty), to monitor the depth of the needle insertion, the remaining stroma, and the interface fluid at the end of the procedure3,4; posterior lamellar corneal transplant surgery (Descemet stripping automated endothelial keratoplasty or Descemet membrane endothelial keratoplasty), for eyes with opaque corneas and difficult graft orientation; assessment of the position of the surgical device in ab interno glaucoma surgery,5 as well as in canaloplasty; and assembly and implantation of Boston keratoprosthesis (S.S., unpublished data, May 2015). Children under general anesthesia with anterior segment anomalies and opacified corneas also seem to benefit from procedure monitoring via intraoperative OCT.6 In posterior segment surgery, Tao et al7 indicated the benefit of intraoperative OCT (eg, during macular hole surgery and vitrectomy). In summary, we see 4 emerging fields where microscopeintegrated intraoperative OCT could be a useful extension of the conventional surgical microscope: (1) in procedures with a reduced anterior chamber view, (2) in procedures where transparent or very thin structures are not readily visible with the microscope, (3) to monitor surgical procedures, and (4) for intraoperative projection of preoperative imaging data onto ocular structures (eg, in macular membrane peeling). In the study by Ehlers et al,8 an overview is presented of several of the aforementioned anterior and posterior segment surgical procedures, including lamellar keratoplasty, cataract surgery, membrane peeling, macular hole surgery, and retinal detachment repair. The authors used the RESCAN 700 OCT device. This device is mounted to the microscope and uses an ocular-integrated image display, as well as an external display. The OCT beam is controlled with a foot-steering mechanism. This study8 analyzes the surgeons’ impressions during the performance of intraoperative OCT for different surgical procedures and assesses the feasibility and effect on surgical decision making of this OCT device. In general, in the majority of cases, OCT provided important information about the procedure and affected the decision-making process of the surgeon. The low rate of cases in which OCT monitoring interfered with the procedure demonstrates that distinct advances have been made in the development of microscope-mounted OCT devices. The majority of the additional OCT findings, not being visible by use of the surgical microscope, were not decisive for further surgical treatment but, in contrast, changed surgical maneuvers substantially for certain procedures. For some types of procedures (such as lamellar keratoplasty, membrane peeling, and macular hole surgery), the findings indicate the importance of future studies to separate indications for which intraoperative OCT is just a novel device from indications for which it really helps the patient and improves outcome. In this study,8 the main adverse events associated with intraoperative OCT were contamination outside the surgical field during the imaging process and surgery delay, which could be reduced by optimizing the OCT systems. Additional problems included the artifacts caused by shadowing of the surgical instruments. This could be avoided in the future by using transparent or coated OCT-compatible instruments. Finally, this study8 underlines the importance of the need for randomized clinical trials regarding the magnitude of the definitive benefit of intraoperative OCT compared with not using the device. These studies should answer the following questions: In which diagnostic or therapeutic intraoperative settings does intraoperative OCT provide a significant benefit in terms of increased safety, efficacy, better outcome, or higher precision of diagnosis? Which type of intraoperative OCT Related article page 1124 Microscope-Integrated OCT During Ophthalmic Surgery Original Investigation Research

Future prospects: assessment of intraoperative optical coherence tomography in ab interno glaucoma surgery.

Abstract Purpose: Ab interno glaucoma surgery, such as trabecular aspiration or ab interno trabeculotomy, has been introduced as an alternative, non-filtering procedure to lower intraocular pressure in glaucoma patients. The purpose of the present study was to assess the feasibility of intraoperative spectral domain optical coherence tomography (iOCT) for improving ab interno glaucoma surgery. Materials and Methods: Intraoperative optical coherence tomography was performed to visualize the anterior chamber angle, the aspiration canula during trabecular aspiration, and the trabectome device during ab interno trabeculotomy. A commercially available 840-nm iOCT was used in a clinical setting, a 1310-nm spectral-domain OCT in an experimental setting. Results: In the clinical setting using the 840-nm iOCT, visualization of the aspiration canula and the trabectome device was possible, however, with rather limited visibility of the chamber angle and the trabecular meshwork. In the experimental setting, the 1310-nm OCT enabled excellent visualization of the chamber angle and detailed evaluation of the instrument–trabecular meshwork relation. Conclusions: Intraoperative use of optical coherence tomography may be helpful for ab interno glaucoma surgery. Adjustments of the commercially available iOCT, including longer wavelengths and oblique scanning options, are necessary for the clinical use.

Development, alteration and real time dynamics of conjunctiva-associated lymphoid tissue

Purpose Conjunctiva-associated lymphoid tissue (CALT) is thought to play a key role in initiating ocular surface related immune responses. This study was planned to get first profound insights into the function of CALT related to development, cellular dynamics and morphological alteration using a novel mouse model. Methods Expression and morphology of CALT were investigated using BALB/c mice kept under different housing conditions, after topical antigen-stimulation and following lymphadenectomy and splenectomy. Particles and bacteria were applied topically to study antigen-transport. Intravital visualization was performed using two-photon microscopy. Results Postnatal development and ultrastructure of CALT in the mouse is similar to humans. Topical antigen-challenge significantly alters CALT expression. Bacterial translocation is demonstrated via lymphoepithelium whereas cellular velocities within follicles were approximately 8 µm/min. Conclusions CALT in the mouse is an immunological interface of the ocular surface, featuring dynamic processes such as morphological plasticity, particle/bacteria transport and cellular migration.

One-year outcome after Descemet membrane endothelial keratoplasty (DMEK) comparing sulfur hexafluoride (SF6) 20% versus 100% air for anterior chamber tamponade

Purpose To investigate 1-year clinical outcome and complication rates following Descemet membrane endothelial keratoplasty (DMEK) with sulfur hexafluoride 20% (SF620%) anterior chamber tamponade compared with conventionally used 100% air for primary graft attachment during DMEK surgery. Methods Records of 1112 consecutive DMEKs were reviewed retrospectively and grouped by anterior chamber tamponade used during DMEK surgery (SF620% vs 100% air). Outcome measures included intraocular pressure (IOP), best spectacle-corrected visual acuity (BSCVA), endothelial cell density (ECD) and central corneal thickness (CCT) at 1, 3, 6 and 12 months after DMEK surgery. Complication rates were assessed, including intraoperative and postoperative complications, and graft detachment rate requiring rebubbling. Results A total of 854 cases were included in this study. In 105 cases (12.3%), DMEK was performed with SF620%, and in 749 cases (87.7%) 100% air was used for anterior chamber tamponade. Outcome results for IOP, BSCVA, ECD and CCT at all follow-up time points were comparable for both anterior chamber tamponade groups without statistical significant differences (p≥0.05), but graft detachment rate requiring rebubbling was significantly lower in the SF620% group (p<0.001). Conclusion Whereas SF620% anterior chamber tamponade does not seem to negatively affect the clinical outcome of DMEK surgery within the first postoperative year, use of SF620% significantly reduces the rate of rebubblings.

Intraoperative Optical Coherence Tomography Enables Noncontact Imaging During Canaloplasty.

Purpose:Here we describe intraoperative optical coherence tomography (iOCT) as a novel noncontact imaging tool for intraoperative monitoring and procedure evaluation during canaloplasty, as a nonpenetrating surgical technique to treat primary open angle glaucoma. Materials and Methods:Retrospective case report of a patient (63 y, female), who underwent traditional canaloplasty, using a commercially available 840 nm OCT device, mounted to an operating microscope (Rescan 700). Main outcome measures were the intraoperative visibility of chamber angle structures and the ability to conduct surveillance of the surgical procedure through the prepared Descemet window, especially correct suture positioning and visible changes of the Schlemm canal after suture tensioning. Results:iOCT delivered high-resolution images during canaloplasty after deep sclerectomy through the prepared Descemet window. All structures of the chamber angle, including the Schlemm canal were visible. Moreover iOCT enabled intraoperative noncontact procedure monitoring and a direct control of the correct localization and changes of the Schlemm canal after suture positioning and tensioning. Conclusions:iOCT seems to be a helpful intraoperative imaging tool during canaloplasty. iOCT allows for noncontact online evaluation of Schlemm canal localization and noncontact evaluation of suture tension. Shadowing of scleral tissue can be avoided by imaging through the routinely prepared Descemet window to visualize chamber angle structures including the implanted suture.

Errata: Advantages of microscope-integrated intraoperative online optical coherence tomography: usage in Boston keratoprosthesis type I surgery.

Boston keratoprosthesis (KPro) type I is a technique to treat patients with corneal diseases that are not amenable to conventional keratoplasty. Correct assembly and central implantation of the prosthesis are crucial for postoperative visual recovery. This study investigates the potential benefit of intraoperative optical coherence tomography (OCT) to monitor KPro surgery. Retrospective case series are presented for two patients who underwent Boston KPro type I implantation. The surgery in both patients was monitored intraoperatively using a commercially available intraoperative OCT (iOCT) device mounted on a surgical microscope. Microscope-integrated intraoperative OCT was able to evaluate the correct assembly and implantation of the KPro. All parts of the prosthesis were visible, and interfaces between the corneal graft and titanium backplate or anterior optics were clearly depictable. Moreover, iOCT visualized a gap between the backplate and graft in one case, and in the other case, a gap between the anterior optic and graft. Neither gap was visible with a conventional surgical microscope. The gap between the anterior optic and the graft could easily be corrected. Microscope-integrated iOCT delivers enhanced information, adding to the normal surgical microscope view during KPro surgery. Correct assembly can be controlled as well as the correct placement of the Boston KPro into the anterior chamber.

Anterior segment optical coherence tomography for the diagnosis of corneal dystrophies according to the IC3D classification

Corneal dystrophies are categorized according to the International Committee for Classification of Corneal Dystrophies (IC3D) classification, and their treatment depends on the affected structures and layer of the cornea. Therefore, estimating the depth and extent of the morphological changes due to the specific dystrophy is crucial when deciding between different treatment options. Besides superficial laser treatments and penetrating keratoplasty, minimal invasive lamellar keratoplasties such as Descemet membrane endothelial keratoplasty, deep anterior lamellar keratoplasty, or Descemet stripping automated keratoplasty have become increasingly popular to exchange the specific opaque layers in dystrophic eyes. To determine the morphological changes of the cornea in the different dystrophies, in addition to slit-lamp examination, anterior segment optical coherence tomography has become an important tool with nearly histological resolution. Nonetheless, only a few case series describe the characteristics of changes seen on anterior segment optical coherence tomography. Therefore, we summarize anterior segment optical coherence tomography signs and correlate with slit-lamp examination, as well as the histopathological findings, of corneal dystrophies according to the IC3D classification.

[Boston-keratoprosthesis : Preliminary experiences in 13 high-risk eyes from the Department of Ophthalmology of the University of Cologne].

BACKGROUND Corneal transplantation in high-risk eyes remains a challenge. The Boston keratoprosthesis (B-KPro) is a final option for patients with end-stage corneal disease and a poor prognosis with conventional penetrating keratoplasty. In this article the results of the first 13 eyes that received a B-KPro type I at the Department of Ophthalmology, University of Cologne, Germany are reported and the usefulness of postoperative slit-lamp optical coherence tomography (SL-OCT) for control purposes is evaluated. MATERIAL AND METHODS All recipients of a B-KPro type I between September 2013 and May 2015 were included in the study. The feasibility of the operation, clinical outcomes, complications and revision surgery were investigated. The visualization of wound healing by SL-OCT was analyzed. RESULTS The age of the patients ranged from 26 to 92 years (mean 57.3 ± 20.9 years). In all 13 eyes from 12 patients (6 males and 6 females) dense corneal opacification with vascularization and sometimes also conjunctivalization was present. Preoperative visual acuity was reduced and ranged from mere light perception up to a maximum of 1/35 eye chart. All 13 eyes could be supplied with a B-KPro type I without any intraoperative complications, in 6 eyes no significant postoperative complications occurred, whereas in 7 eyes various additional surgical interventions were required and 1 B-KPro could not be preserved. Postoperative visual acuity ranged from light perception to 20/32 and was significantly improved in 85 % of the treated eyes. The use of SL-OCT reproducibly allowed the postoperative assessment of stromal thinning. CONCLUSION The B-KPro provides the possibility of visual rehabilitation in high-risk eyes that could never be achieved without artificial cornea replacement. Despite higher complication rates this technique represents a significant progress in the surgical treatment of complex corneal pathologies. Regular and intensive postoperative controls are necessary to achieve good long-term results.

Pediatric corneal surgery and corneal transplantation

ZusammenfassungDie operative Therapie kindlicher Hornhauterkrankungen stellt auch für den erfahrenen Hornhautchirurgen eine Sondersituation dar. Neben der generell erschwerten Befunderhebung bei Kindern sind die Hornhaut und die angrenzende Sklera bei Säuglingen und Kleinkindern noch sehr weich, wodurch beispielsweise bei Keratoplastik die wunddichte Nahtlegung erschwert ist. Intraoperativ sorgen die flache Augenvorderkammer im kleinen kindlichen Auge und der typischerweise recht hohe Glaskörperdruck für enge Platzverhältnisse und wenig Spielraum für chirurgische Manipulationen. Frühe Fadenlockerungen, ein erhöhtes Risiko von postoperativen Fibrinreaktionen sowie immunologischen Transplantatreaktionen nach Keratoplastik und die drohende Amblyopiegefahr machen intensive Kontrollen, teilweise unter Narkose, notwendig. Gerade bei den sehr kleinen Patienten bieten lamelläre chirurgische Verfahren wesentliche Vorteile, da hierdurch die Gefahr von Abstoßungsreaktionen reduziert und durch die geringere Invasivität des Eingriffs bei anterioren lamellären Techniken keine bzw. nur eine geringe Eröffnung der Augenvorderkammer erfolgt. Die schnellere Herstellung optisch klarer Medien bei posterioren lamellären Techniken reduziert darüber hinaus die Amblyopiegefahr.AbstractThe surgical treatment of congenital corneal diseases or corneal diseases occurring during infancy is demanding even for experienced corneal surgeons. Besides the need for frequent examinations under anesthesia during the postoperative follow-up in young children and infants (e.g. after corneal transplantation), the surgeon frequently encounters intraoperative and postoperative problems, such as low scleral rigidity, positive vitreous pressure and a narrow anterior chamber. Other problems include increased fibrin reaction, an increased risk of rejection in cases of allogenic corneal transplantation and frequent loosening of sutures necessitating replacement or early removal. Lamellar corneal transplantation reduces the risk of graft rejection and the risk of wound leakage. Moreover, posterior lamellar keratoplasty in children offers a faster visual recovery compared to penetrating keratoplasty and thus reduces the risk of amblyopia.The surgical treatment of congenital corneal diseases or corneal diseases occurring during infancy is demanding even for experienced corneal surgeons. Besides the need for frequent examinations under anesthesia during the postoperative follow-up in young children and infants (e.g. after corneal transplantation), the surgeon frequently encounters intraoperative and postoperative problems, such as low scleral rigidity, positive vitreous pressure and a narrow anterior chamber. Other problems include increased fibrin reaction, an increased risk of rejection in cases of allogenic corneal transplantation and frequent loosening of sutures necessitating replacement or early removal. Lamellar corneal transplantation reduces the risk of graft rejection and the risk of wound leakage. Moreover, posterior lamellar keratoplasty in children offers a faster visual recovery compared to penetrating keratoplasty and thus reduces the risk of amblyopia.

Transient Ingrowth of Lymphatic Vessels into the Physiologically Avascular Cornea Regulates Corneal Edema and Transparency

Lymphangiogenesis is essential for fluid homeostasis in vascularized tissues. In the normally avascular cornea, however, pathological lymphangiogenesis mediates diseases like corneal transplant rejection, dry eye disease, and allergy. So far, a physiological role for lymphangiogenesis in a primarily avascular site such as the cornea has not been described. Using a mouse model of perforating corneal injury that causes acute and severe fluid accumulation in the cornea, we show that lymphatics transiently and selectively invade the cornea and regulate the resolution of corneal edema. Pharmacological blockade of lymphangiogenesis via VEGFR-3 inhibition results in increased corneal thickness due to delayed drainage of corneal edema and a trend towards prolonged corneal opacification. Notably, lymphatics are also detectable in the cornea of a patient with acute edema due to spontaneous Descemet´s (basement) membrane rupture in keratoconus, mimicking this animal model and highlighting the clinical relevance of lymphangiogenesis in corneal fluid homeostasis. Together, our findings provide evidence that lymphangiogenesis plays an unexpectedly beneficial role in the regulation of corneal edema and transparency. This might open new treatment options in blinding diseases associated with corneal edema and transparency loss. Furthermore, we demonstrate for the first time that physiological lymphangiogenesis also occurs in primarily avascular sites.