|Year : 2016 | Volume
| Issue : 1 | Page : 20-22
Role of real-time intraoperative optical coherence tomography in lamellar corneal surgeries
Rajesh Sinha, Tarun Arora
Lens and Refractive Surgery Services, R P Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
|Date of Web Publication||11-Nov-2016|
Lens and Refractive Surgery Services, R P Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi
Source of Support: None, Conflict of Interest: None
Real-time intraoperative optical coherence tomography (iOCT) integrated into the operating microscope can be used for optimizing the outcome of lamellar corneal surgeries. Surgical technique can be modified intraoperatively by its use, and surgical endpoint can be achieved in the operating room itself. We have successfully utilized the use of iOCT for refining the endpoint of surgical procedures such as deep anterior lamellar keratoplasty, descemet stripping automated endothelial keratoplasty, descemet membrane endothelial keratoplasty, and superficial anterior lamellar keratoplasty. Continuous iOCT imaging is a new technique that allows an accurate estimation of the depth of dissection, aiding in the modification of surgical planning.
Keywords: asOCT; iOCT; lamellar corneal surgeries.
|How to cite this article:|
Sinha R, Arora T. Role of real-time intraoperative optical coherence tomography in lamellar corneal surgeries. Kerala J Ophthalmol 2016;28:20-2
|How to cite this URL:|
Sinha R, Arora T. Role of real-time intraoperative optical coherence tomography in lamellar corneal surgeries. Kerala J Ophthalmol [serial online] 2016 [cited 2019 Aug 22];28:20-2. Available from: http://www.kjophthal.com/text.asp?2016/28/1/20/193864
| Introduction|| |
Real-time intraoperative optical coherence tomography (iOCT) integrated into the operating microscope is increasingly finding role in the field of lamellar corneal surgeries. It enhances visualization and helps in surgical decision-making. Modification of the surgical procedure can be performed, if required, and confirmation of the surgical endpoint can be achieved in the operating room itself. In the last few years, advantages of iOCT have been reported in various case scenarios related to both anterior and posterior lamellar corneal surgeries. iOCT is particularly helpful for visualization in the presence of corneal edema or scar because the infrared illumination used by OCT scatters less than the visible light used by standard ophthalmic microscopes. Real-time iOCT imaging can be performed using a microscope-integrated iOCT system (RESCAN 700; Carl Zeiss Meditec, Oberkochen, Germany). This integrated system includes a “heads-up display” with a visible transparent overlay of the OCT data stream in the surgeon's right ocular and an external video display panel. Surgeon foot-pedal control or external assistant control is also possible in this system.
Based on scientific literature and our personal experience, we have assessed various advantages and limitations of iOCT in lamellar corneal surgeries.
Intraoperative optical coherence tomography in deep anterior lamellar keratoplasty
iOCT plays the role of surgeon's third hand as it permits live or real-time monitoring during surgery, especially if it is necessary to estimate depth or if the view of anterior chamber is limited. The technology has shown great potential, especially in performing deep anterior lamellar keratoplasty (DALK). In cases with irregular corneal scarring and thinning, iOCT can help to determine the initial trephination depth so as to avoid a perforation and reach an adequate depth to achieve a big bubble. iOCT permits depth estimation during deep needle or cannula insertion before air injection so as to maximize the possibility of achieving the big bubble. After the big bubble is achieved, the descemet's membrane (DM) is seen as a separate layer from the corneal stroma [Figure 1]. On creating a full thickness incision through the stroma, the DM can be visualized coming back up towards its normal position. On injecting viscoelastic through the incision, DM again separates from the stroma. De Benito et al. also highlighted its advantage for viscodissection assisted DALK where they could visualize the exact location of DM in relation to viscoelastic. In cases of manual dissection, the depth of dissection can be estimated and therefore regular dissection can be performed. Knowing the exact level of dissection also helps to prevent rupture of DM. Therefore, each step of the surgery can be clearly visualized with the help of iOCT. It also allows the visualization of intraoperative interface fluid at the end of the surgery.
|Figure 1: Descemet membrane can be seen separated from the corneal stroma after the big bubble is achieved|
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The use of iOCT for the successful management of descemet's membrane detachment (DMD) following DALK with intracameral injection of 20% sulphur hexafluoride has also been recently described. Continuous real-time monitoring of the change in height of the detached DM was observed to ensure the surgical endpoint. Stab incisions were given through the anterior cornea due to the presence of residual fluid above the DM, which were also visible on continuous iOCT imaging. iOCT helps to visualize the advancing edge of the needle beneath the DM before the gas is injected.
Intraoperative optical coherence tomography for descemet stripping automated endothelial keratoplasty
In cases of severe bullous keratopathy, the chronic significant corneal edema can compromise the necessary intraoperative views using standard microscope illumination. iOCT helps in visualization of DM remnants [Figure 2] in such hazy cornea after host DM stripping has been performed. iOCT confirms the presence of the graft in the anterior chamber, its configuration (edges folded/unfolded), its relative location to the host cornea, and the presence or absence of interface fluid [Figure 3] to ensure adequate graft-host adherence.
|Figure 2: Visualization of DM remnants in a hazy cornea after descemet's stripping has been performed|
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|Figure 3: Well-apposed donor graft in a case of endothelial keratoplasty with no interface fluid|
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Intraoperative optical coherence tomography for descemet membrane endothelial keratoplasty
Similar to DSAEK, the implementation of iOCT for descemet membrane endothelial keratoplasty (DMEK) may provide information to the surgeon that helps improve tissue apposition and orientation while minimizing unnecessary and potentially dangerous manipulation of the donor scroll. In a study performed by Cost et al., the graft orientation was rapidly identifiable with intraoperative OCT in 100% of cases based on the rolling behavior of the graft. iOCT was also used to evaluate graft apposition and the impact of external sweeping on interface fluid, when visible.
Intraoperative optical coherence tomography for superficial anterior lamellar keratoplasty
iOCT can help in cases of suture-less superficial anterior lamellar keratoplasty (SALK) by aiding in the visualization of smoothness and level of dissection of both donor and host cornea [Figure 4]. It also helps in the visualization of graft host edge apposition [Figure 5], and graft exchange can be performed in cases of malposition.
|Figure 4: Superficial anterior lamellar keratoplasty performed in a case of macular corneal dystrophy|
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|Figure 5: Well-apposed graft host edge in the case discussed in Figure 4|
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Depending on the system used, there may be limitations in the depth and lateral extent of the OCT scans. With the current iOCT systems, automated tracking to areas of interest is not available. In addition, software analysis of fluid dynamics is not available. As of now, the iOCT provides only qualitative details without providing the quantitative measurements of the anterior segment instantly. To overcome limits in field of view, the OCT scan should be moved to specific areas of interest such as the central or peripheral cornea. Metallic instruments and air obscure the underlying OCT image acquisition, and thereby preclude complete visualization. High expense of the technology prohibits its widespread use.
| Conclusion|| |
Continuous iOCT imaging is a new tool in the armamentarium of the lamellar corneal surgeons. This allows an accurate estimation of the depth of dissection and aids in the modification of surgical planning. In future, introduction of tools for quantitative analysis will provide a new dimension to this technology.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Pasricha ND, Shieh C, Carrasco-Zevallos OM, Keller B, Izatt JA, Toth CA, et al
. Real-Time Microscope-Integrated OCT to Improve Visualization in DSAEK for Advanced Bullous Keratopathy. Cornea 2015;34:1606-10.
Siebelmann S, Steven P, Cursiefen C. Intraoperative Optical Coherence Tomography In Deep Anterior Lamellar Keratoplasty. Klin Monbl Augenheilkd 2016;233:717-21.
De Benito-Llopis L, Mehta JS, Angunawela RI, Ang M, Tan DT. Intraoperative anterior segment optical coherence tomography: A novel assessment tool during deep anterior lamellar keratoplasty. Am J Ophthalmol 2014;157,:334-41.
Sharma N, Aron N, Kakkar P, Titiyal JS. Continuous intraoperative OCT guided management of post-deep anterior lamellar keratoplasty descemetthy. estimation of the dSaudi J Ophthalmol 2016;30:133-6.
Cost B, Goshe JM, Srivastava S, Ehlers JP. Intraoperative optical coherence tomography-assisted descemet membrane endothelial keratoplasty in the DISCOVER study. Am J Ophthalmol 2015;160:430-7.
[Figure 1], [Figure 2, [Figure 3], [Figure 4], [Figure 5]