OCT in the OR: Using OCT During Retina Surgery

Optical Coherence Tomography (OCT) has revolutionized the practice of ophthalmology, becoming a mainstay of modern clinical practice. The advancement from time-domain OCT to spectral and swept-source OCT has further refined diagnosis and pre- and post-operative management for many conditions, including diabetic retinopathy, macular degeneration, retinal vein occlusions, etc. Utilizing the OCT intraoperatively (iOCT) has been viewed as the next frontier in the application of OCT, with recent advancements providing increased promise moving forward.

The transition from handheld to microscope mounted to now microscope-integrated iOCT represents major leaps towards more widespread implementation of iOCT. Early studies show promising results for utilizing iOCT in both anterior and posterior segment surgeries. This article discusses the background, practical clinical applications, and challenges of utilizing iOCT with a particular focus on the posterior segment.

OCT in the intraoperative setting

OCT is a cross-sectional imaging tool that is rapid and non-invasive, utilizing reflected light to obtain images of different layers of intraocular tissues. Initially, a major barrier to using OCT in the intraoperative setting was the size of the OCT machine themselves. This barrier necessitated the creation of handheld or portable OCT machines to be utilized in the OR. A major issue with these portable OCTs was that the surgeon had to pause from surgery and move the patient to take images. That issue has been resolved with the advent of the microscope-integrated OCT, which allows for more live integrated imaging.

DISCOVER and PIONEER: studies in practical clinical applications in posterior segment cases

While iOCT has shown promise and benefit for various anterior segment surgeries such as DMEK, DSEK, and corneal biopsy,¹ we will focus our discussion on the posterior segment.

To start, Chavela et al were able to consistently obtain valuable subclinical anatomical information including subretinal membranes and retinoschisis utilizing iOCT.² Pfau et al. conducted a prospective study looking at 40 surgical cases undergoing posterior segment surgery, finding that additional information was provided in nearly 75% of cases and that surgical decision-making was affected or changed in over 40% of cases due to iOCT findings.³ Faulkner et al. examined 51 patients with epiretinal membranes undergoing surgery, finding that membranes could be identified in around 40% of cases without dyes such as brilliant blue G or indocyanine green.⁴

Two other major studies, the DISCOVER and PIONEER studies, looked at both anterior and posterior segment surgeries and iOCT, with promising findings. Both studies demonstrated that information provided by iOCT impacted decision-making in a significant number of cases.

PIONEER was a 2-year study featuring 532 eyes and primarily examined membrane peeling, finding nearly 10% of surgeons felt the iOCT affected their surgical decision making, and 43% of cases were affected by information provided by the iOCT, without any adverse events.⁵

DISCOVER was a larger 3-year, single-center, multi-surgeon study that looked at over 2100 eyes, finding the value of iOCT in describing and identifying membrane borders, distinguishing between partial and full-thickness holes, confirming epiretinal membrane peel completion, and more. In the DISCOVER study, surgical decision-making was altered in nearly a third of cases based on iOCT feedback.⁶ These decision-making changes ranged in scope from identifying full-thickness holes, targeting precise chorioretinal biopsy sites, and limiting the need for additional staining.⁶

Additionally, the DISCOVER study revealed that iOCT helped surgeons identify residual membranes, even when surgeons believed they had removed all membranes (in over 15% of cases studied).⁶ iOCT also assisted in the reverse, helping confirm completion of membrane peels when the surgeon felt there still may be membranes to peel (in 20% of cases studied).⁶ In over 20% of RD cases iOCT led to changes in surgical plan, including changing retinotomy sites and assisted in distinguishing between subretinal fluid vs hemorrhage.⁶ Overall, nearly 30% of posterior segment surgeries were affected by the presence of the iOCT in the DISCOVERY trial, in the ways mentioned above.⁶

These findings all suggest the iOCT has value in bridging the gap between surgeon perception and anatomical reality. Bridging this gap means less likelihood of iatrogenic macular holes, superior endpoint visualization, less reliance on stains/dyes, better visualization of the presence of subretinal fluid, better able to distinguish between areas of detachment from schisis, and increased detection of smaller retinal breaks.

In addition to the above, the iOCT has shown the ability to provide additional information about tissue configuration and precise location for intervention in proliferative diabetic retinopathy, vitreous hemorrhage, retinal prosthesis placements, retinal biopsies, and targeted stem, gene, and pharmacotherapy.^7-13

Future challenges for posterior segment iOCT

While there is potential and promise with recent progress to microscope-integrated OCT, there are still some challenges facing iOCT in its current form. These challenges include the cost of the integrated technology, limited visualization of peripheral retina, overall image quality, OCT compatible tools (in particular tools that do not create shadows), and instrument tracking.

Perhaps most important, there is greater external validation needed to justify the inclusion of iOCT as the standard of practice.

It is important to highlight that currently, whether or not iOCT imaging is used intraoperatively, the reimbursement from insurance for the surgery performed would not be altered.

Conclusions

At the minimum, iOCT provides additional information in a vast majority of cases in which it is utilized. Oftentimes, this information translates to altered decision-making by the surgeon. More accurate and thorough visualization is just the beginning, however, as iOCT also provides the opportunity for cost efficiency through reducing unnecessary surgical steps and shows potential for superior outcomes from safer and more precise procedures.

While some challenges remain with regards to software, image quality, and tool refinement, rapid advances and hopefully reduced costs will lead to increased adoption of iOCT.

While it is estimated that only around a quarter of surgeons currently utilize iOCT, leading experts agree that it is likely with the advent of microscope-integrated iOCT that iOCT will become a commonly used tool for surgical decision making,¹⁴ just as OCT in the clinics currently guides many clinical decisions on a daily basis.

References

Review of intraoperative optical coherence tomography: technology and applications [Invited] (nih.gov).
Chavala SH, Farsiu S, Maldonado R, Wallace DK, Freedman SF, Toth CA. Insights into advanced retinopathy of prematurity using handheld spectral domain optical coherence tomography imaging. Ophthalmology. 2009 Dec;116(12):2448-56.
Pfau M, Michels S, Binder S, Becker MD. Clinical experience with the first commercially available intraoperative optical coherence tomography system. Ophthalmic Surg Lasers Imaging Retina. 2015;46(10):1001-1008.
Falkner-Radner CI, Glittenberg C, Gabriel M, Binder S. Intrasurgical microscope-integrated spectral domain optical coherence tomography-assisted membrane peeling. Ophthalmol Retina 2015;35(10):2100-2106.
Ehlers JP, Dupps WJ, Kaiser PK, Goshe J, Singh RP, Petkovsek D, Srivastava SK. The Prospective Intraoperative and Perioperative Ophthalmic ImagiNg with Optical CoherEncE TomogRaphy (PIONEER) Study: 2-year results. Am J Ophthalmol. 2014 Nov;158(5):999-1007. doi: 10.1016/j.ajo.2014.07.034. Epub 2014 Jul 29. PMID: 25077834; PMCID: PMC4250395.
Ehlers JP, Modi YS, Pecen PE, Goshe J, Dupps WJ, Rachitskaya A, Sharma S, Yuan A, Singh R, Kaiser PK, Reese JL, Calabrise C, Watts A, Srivastava SK. The DISCOVER Study 3-Year Results: Feasibility and Usefulness of Microscope-Integrated Intraoperative OCT during Ophthalmic Surgery. Ophthalmology. 2018 Jul;125(7):1014-1027. doi: 10.1016/j.ophtha.2017.12.037. Epub 2018 Mar 2. PMID: 29409662; PMCID: PMC6015779.
Intraoperative OCT: An Emerging Technology - American Academy of Ophthalmology (aao.org).
Use of a new intra-ocular spectral domain optical coherence tomography in vitreoretinal surgery - PubMed (nih.gov).
The Value of Intraoperative OCT Imaging in Vitreoretinal Surgery (nih.gov)
Falkner-Radner CI, Glittenberg C, Gabriel M, Binder S. Intrasurgical microscope-integrated spectral domain optical coherence tomography-assisted membrane peeling. Ophthalmol Retina 2015;35(10):2100-2106.
Gregori NZ, Lam BL, Davis JL. Intraoperative use of microscope-integrated optical coherence tomography for subretinal gene therapy delivery. Retina 2019.
Ehlers JP, Petkovsek DS, Yuan A, et al. Intrasurgical assessment of subretinal tPA injection for submacular hemorrhage in the PIONEER study utilizing intraoperative OCT. Ophthalmic Surg Lasers Imaging Retina 2015;46:3:327-32.
Ehlers JP, Ohr MP, Kaiser PK, et al. Novel microarchitectural dynamics in rhegmatogenous retinal detachments identified with intraoperative optical coherence tomography. Retina 2013;33:7:1428-34.
Khan M and Ehlers JP. Curr Opin Ophthalmol. 2016;27(3):201-209.