Article

iOCT for Anterior Segment Surgery

The value of visualization, particularly for complex cases

Even among those of us who routinely perform anterior segment surgery, not many have observed real-time intraoperative OCT, also known as iOCT. Sightings are not quite as rare as, say, Big Foot or a jackalope, but they are rare nonetheless. That’s why I’d like to share some cases where I’ve used the real-time iOCT integrated with my surgical microscope (OPMI Lumera 700, Zeiss) to get the surgical advantage of anterior segment OCT views without any disruption in surgery. I practice in a referral setting, so I often find myself operating on complex cases, many times with a retina surgeon. iOCT helps ensure we can see in these difficult cases.

Complex anterior segment surgery + retina surgery: When we combine a complex anterior segment surgery with a retina procedure, my retina colleague and I can both see clearly with our microscope by making a push-button switch between views. We can also use anterior segment iOCT with the same scope, making for a very smooth workflow.

Cataract surgery + endothelial keratoplasty: In endothelial keratoplasty, or Descemet’s stripping endothelial keratoplasty (DSEK), we transplant a thin lens ovule of posterior cornea onto the cornea (about 100 microns). To combine DSEK with cataract surgery, we perform cataract surgery as we usually do, with a small change in the size of the capsulorrhexis. As we score the endothelium, the overlaid iOCT allows us to visualize the removal of Descemet’s. We can also visualize the endothelial graft in the anterior chamber as well as its displacement against the posterior cornea with air bubble injection.

Most importantly, we can visualize the interface between the endothelial graft and the overlying stroma, which is impossible without using iOCT. The objective is to remove all fluid from the graft-host stromal interface. I’ve been surprised to find that sometimes, when I think all of the fluid is removed, iOCT shows there’s still a pocket of fluid at the interface. And had we not caught that fluid, the patient might have returned with a dislocation of the graft.

Seamlessly Moving Data

New diagnostic technologies are altering the traditional barrier between the clinic and the OR. We’ve seen data transfer evolve over the past few years. Taking a picture in the office and carrying it with us in some form to the OR just doesn’t work. Now we have an automatic flow of data from office diagnostics to the OR. I think the unit that will integrate the technologies will be the microscope, and it’s going to make our lives so much easier.

Today, when I go to the OR, I’ve got my iPad as well as my cell phone, so I can call the office and get data if I want to make a change on the fly. I’ve always been anxious to get more data transfer into the OR to help me make decisions.

The Forum system (Zeiss) transfers the data, so surgeons don’t have to take images and cell phones to the OR. It puts all of the patient’s data at our fingertips, prevents potential data entry errors, and eliminates potential HIPAA issues associated with carrying records between locations. As we aim to eliminate paper by transferring data seamlessly between machines and locations, we will also improve patient safety and work more efficiently.

Complex retinal detachment: iOCT gives us a few advantages in complex anterior segment cases. In one particular case, the patient had three previous retinal detachment repairs. He was aniridic, with two tube shunts, so I needed to make sure the interface was free of any fluid. The patient was only 8 years old, so I wanted to get it right the first time to minimize his risk for return to the operating room.

Through the microscope, iOCT images are highlighted above and to the side of the surgical field, so I can see what I’m doing and refer to the iOCT images in real time. For this patient, I was very careful to ensure the interface was gone, minimizing the chance of dislocation the next day. iOCT made that visualization possible, and the patient did well with no repeat air bubble.

Corneal Transplant with DMEK: When performing Descemet membrane endothelial keratoplasty (DMEK) with a partial thickness (12 μm) corneal transplant, visualization has always been a problem. The procedure is a bit of a different beast as compared to DSEK. We have a very thin endothelial graft that wants to curl up on itself into a scroll or double scroll, and we have to unfold it in the correct orientation. We stain and mark the graft, but it still can be very challenging to complete the surgery.

With iOCT, I can see the graft and its orientation in the eye. As soon as the graft is placed, I use iOCT to see the shape and orientation of the graft, which allows me to know how best to unscroll it. At the end of the case, I can once again visualize the DMEK graft with its edges scrolling upward toward the posterior cornea. That’s how you know the graft is in the correct orientation. Even at a time when eye bank preparation is so advanced, I’ve seen grafts with poor staining or stromal marks that fade or can’t be seen during surgery, so I rely on iOCT.

iOCT even lets us see the capsular bag. In many cases, we’re performing cataract surgery in patients who have edematous corneas, and it can be difficult to judge depth in the anterior chamber. With iOCT, we can look into the lens and see the groove we’re making. If we’re teaching residents, we can show them and say, “Look — you’re only 10% into the lens.”

Penetrating keratoplasty: Many patients who need advanced corneal transplant surgery have disorganized anterior segments. For example, I had a young patient with chronic uveitis, extensive fibrosis, and disorganization of the anterior segment. I wasn’t sure what was going on inside the eye. iOCT showed a dense fibrotic membrane over the patient’s intraocular lens and extensive peripheral anterior synechia. With this knowledge, I was able to formulate a surgical plan prior to removal of the cornea. Once the cornea was removed, the iOCT was used to highlight the fibrous membrane, helping me slowly and meticulously dissect it, freeing the IOL and opening the angle. Once the cornea was placed, the angle was deep with a well-positioned lens. In this case, iOCT allowed a more successful surgical procedure with reduced risk of transplant failure.

ADDED EFFICIENCIES OF iOCT

Whenever we choose new technology, it has to improve our outcomes and increase efficiency. Real-time iOCT in surgery gives us the ability to make surgical decisions on the fly without stopping, checking our images, and returning to surgery. This is a benefit to anterior segment surgery, even empowering me to take on cases I may not have tackled without it. Visualization of structures in the anterior segment gives me confidence to perform complex cases with more confidence. It’s like having x-ray vision in the operating room. ■