Ophthalmology

PARIS — Intrasurgical optical coherence tomography improves intraoperative evaluation of vitreoretinal conditions, facilitates surgery and supports the surgeon’s decision-making process, thus improving surgical outcome, according to a specialist.

“Intraoperative imaging provides immediate information about structural changes during surgery, such as tissue movements, the influence of fluid dynamics and the amount of surgical trauma,” Susanne Binder, MD, said at the Euretina meeting. “All this in a perfectly safe way, without loss of sterility. It also allows examination of patients who are unable to sit upright, such as ROP babies.”

In order to clarify indications for intraoperative OCT, 512 × 128 macular cube scans of 50 eyes of 50 patients were acquired at various stages of surgery, using the Carl Zeiss Meditec Cirrus HD-OCT system adapted to the optical pathway of a Zeiss OPMI VISU 200 surgical microscope with 60D BIOM lens.

“OCT guided our surgery in a variety of situations, such as pars plana vitrectomy with membrane peeling (35 cases), combined or not with cataract surgery and IOL implantation, macular pucker (23 cases), penetrating macular hole (12 cases), retinal detachment (three cases), silicone oil removal (two cases) and cataract surgery alone (12 cases). We were able to acquire intraretinal scans of sufficiently good quality for all the patients,” Dr. Binder said.

Dr. Binder and her colleagues sought answers to questions such as whether the quality of intrasurgical OCT is comparable to that of preoperative OCT, whether surgical manipulation can be observed and whether the amount of surgical trauma can be estimated.In addition, they sought to “verify how precisely we could visualize the outcomes: whether membrane peeling was complete, how was the retina at the end of surgery, whether or not there was a foveal involvement and whether there was any residual subretinal fluid under silicone oil.”

Dr. Binder and colleagues found that intrasurgical OCT was comparable to preoperative OCT in terms of image quality.

“Image quality was excellent and we could visualize details with extreme clarity,” she said.

Benefits of OCT

Surgical maneuvers could be closely observed as they were performed, and this helped in calibrating manipulation and controlling the immediate effects of maneuvers on the eye structures.

“In one case of stage 2 macular hole with a traction, I was able to control the traction force. I decided to remove the membrane with scissors at the end, so I did not de-roof the macular hole. The amount of surgical trauma could be estimated immediately at the beginning, during and at the end of membrane peeling,” Dr. Binder said.

In another case, it was possible to see how complete membrane peeling was. The extension of the membranes and the loss of foveal contours could be seen at the beginning of surgery. At the end of the procedure, a second look was taken in the nasal contour for residual membrane. The 3-D scan of the postoperative processing confirmed some wrinkling of the retina, but the retina itself was clean.

The condition of the retina can be continuously watched during the entire process of membrane peeling.

“Again, at the end of surgery you can double-check, in 3-D, the membrane you have removed and the retinal condition you have left when you have removed the tissue. You will be surprised to see that what you leave is a totally nice flat retina that looks very different,” Dr. Binder said.

Intrasurgical OCT can also visualize features that are not detected clinically, she said.

In a myopic patient with a nasally superior retinal detachment, a dry macula was diagnosed by clinical observation.

“Visual acuity was 20/40, so, why not? He also had a little bit of a cataract. But what we could see at the beginning of surgery was that he had a detached macula when he was in the lying position. I strongly believe we will no longer be able to differentiate macula on and off by clinical observation only,” Dr. Binder said.

The 3-D scan also showed a retinal detachment up to the fovea and only a partial vitreous detachment. This explained why primary vitrectomy was difficult, due to the large parts of attached vitreous.

Future of OCT use

Intrasurgical OCT is a promising examination method that can help greatly during surgery, Dr. Binder said.

“The instrument needs further improvement. The scan line indicator will need to be implemented into the visual field of the surgeon. Now we have to look into two different screens. We also need tracking systems,” she said. – by Michela Cimberle

• Susanne Binder, MD, can be reached at Department of Ophthalmology, Ludwig Boltzmann Institute for Retinology and Biomicroscopic Laser Surgery, Rudolph Foundation Clinic, Juchgasse 25, 1030 Vienna, Austria; +43-1-71165-4607; fax: +43-1-71165-4609; e-mail: susanne.binder@wienkav.at.
• Disclosure: Dr. Binder has no financial interest in the products discussed in this article, nor is she a paid consultant for any companies mentioned.

Intraoperative OCT is a promising and exciting new imaging procedure that is in the early stages of development and refinement. Currently, the only commercially available units that can be feasibly used in the operating room are handheld units or modified table-top systems. Various intraoperative OCT prototypes are currently being studied. The development of a seamlessly integrated OCT system into the operating theater is the ultimate goal that will hopefully impact our understanding of vitreoretinal surgical diseases and improve our clinical outcomes. We are just beginning to describe some of the findings associated with various surgical vitreoretinal diseases and the impact of our surgical maneuvers on these conditions. Intraoperative OCT has also begun to reveal important new information regarding the pathophysiology of certain retinal diseases. Extensive research is still needed to further understand the role for intraoperative OCT and its impact on clinical outcomes. Areas of important future research include rapid scan targeting, OCT-friendly instrumentation, heads-up display systems, imaging protocols for dynamic intraoperative imaging and identification of critical feedback information to the surgeon.

Finally, studies are needed to verify the utility of this technology, not only in providing more information regarding pathophysiology, but also in improving functional and anatomic outcomes.

— Justis P. Ehlers, MD
Vitreoretinal Service, Cole Eye Institute, Cleveland Clinic, Cleveland, USA
Disclosure: Dr Ehlers has no financial interest in the products discussed in this article.