The standard approach to retinal photocoagulation, commonly used to manage proliferative diabetic retinopathy, vein occlusions and diabetic macular edema, involves examining fundus images to determine targets and then treating the patient at the slit lamp. Now, a new system from German company OD-OS al-lows surgeons to manage the entire process using a single computerized platform, with onscreen imaging and choosing of targets, and computer-guided lasering. The system is called Navilas, short for navigated laser. It received approval from the Food and Drug Administration in November 2009. (Another system based on the same premise is under development by Vantage Surgical Systems in Los Angeles; they hope to have their product on the market within a year or two.)
|With a computer as the middleman, this system allows the surgeon to choose targets onscreen, deliver precision treatments and document digitally.|
Here’s how Navilas works: First, the instrument captures 35- or 50-degree-field images of the retina—panable across the fundus—in any one of several modes (true-color, infrared, red-free or fluorescein angiography). Then, the surgeon marks the desired targets, as well as any areas to avoid, on the onscreen image using either a touch screen or the mouse. Target areas can be marked as spots, ranging in size from 50 µm to 500 µm, or as any one of a number of customizable shapes or patterns.
When the surgeon and patient are ready to proceed with lasering, the system begins capturing live video images of the retina (mydriatic or non-mydriatic) at 25 frames per second, and overlays the stored image that shows the marked targets on top of the live image. The surgeon then turns off the original image; the target markings remain, now transferred and locked onto the live video image. Eye-tracking software maintains registration during the procedure.
Next, the system locks onto each target one at a time, beeping when it’s locked on, and the surgeon, via footpedal, performs 532-nm laser photocoagulation on the intended targets while watching the live video onscreen. During the procedure the retina can be imaged in infrared mode, which is more comfortable for the patient than the bright white slit-lamp light. This produces a black and white image onscreen; however, the system allows the surgeon to toggle back and forth to a color fundus view to determine the intensity of each burn and adjust the power as necessary. If the patient closes his eye or any other circumstances cause registration to be interrupted, the laser stops firing.
Finally, the system provides digital documentation of the entire procedure, including images of each laser application, marked with circles, and the laser parameters used at each location.
The Physician’s Perspective
William R. Freeman, MD, professor and director of the University of California-San Diego’s Jacobs Retina Center at the Shiley Eye Center, in La Jolla, Calif., was one of the clinical investigators for the device. (He is a consultant for the company, but has no financial stake in the instrument.) “In our hands, this treatment method is more accurate and reliable than manual lasering at the slit lamp,” he says. “We reviewed the video records the instrument provides to see how many of 400 targeted microaneurysms we actually hit in a group of patients; our accuracy rate was 92 percent. The laser was never more than 150 µm off, and some of those near misses were the result of physician error—imperfect placement of the target spots. This level of accuracy is better than we’ve been able to achieve with the slit lamp.”
Rama D. Jager, MD, a partner at University Retina and Macula Associates of Oak Forest, Ill., and clinical assistant professor of ophthalmology at the University of Chicago, says his practice has owned the Navilas system for about four months and has used it to treat more than 75 patients. (He has no financial connection to the company or product.) Although switching to the system takes a little getting used to, Dr. Jager says his practice has found it to have a fairly short learning curve. “It’s different from what you were taught as a resident or fellow,” he notes.
Dr. Freeman agrees. “It’s a bit like switching from a film camera with a little viewfinder to a digital camera that you hold farther away and look at the screen,” he says. “However, doctors who have any experience with a fundus camera should find it very instinctive.”
Dr. Jager says the system allows him to plan things out more carefully and achieve better results in a shorter amount of time. “Because of the eye tracker, I don’t have to tell the patient to stop moving,” he notes. “In addition, my tension level is reduced because I know exactly where the laser is aiming and the machine guides me to the next spot.
“I think a lot of surgeons using focal laser treatments shy away from areas that are close to the fovea simply because of their fear of hitting it,” he continues. “This system helps to eliminate some of that fear because of the eye-tracker technology, and the ability to create “no burn” zones that the laser will then avoid. Furthermore, I can take quick images to make sure the burn intensity I’m using isn’t too hot or cold.
“The system also aids documentation,” he notes. “Many surgeons document these procedures by drawing a diagram with a few Xs here and there. With this, you’re able to pinpoint exactly where you’ve lasered on an actual picture of the fundus.”
Dr. Freeman says that he now rarely uses a contact lens, because patients don’t blink constantly with the infrared light instead of the bright slit-lamp light. “If they do blink, the laser won’t fire,” he points out. “This is more comfortable for the patient. In fact, patients are happy to have the other eye done in the same session. It’s also easier for me because I have two hands free, and I find it easier to look at a screen than through the slit lamp. I see the entire fundus, not just a narrow slit of light.”
On the downside, Dr. Jager says the cost is an issue, especially in the current economic climate. “It’s an expensive piece of equipment, and it doesn’t add anything to the bottom line from the perspective of a private practice,” he says. “We bought it because we felt it would be better for our patients.” (A spokesman for the company says the Navilas can be purchased in the United States for an initial investment of $120,000; ongoing costs for software, hardware support and the use license will depend on volume.)
Beyond that concern, Dr. Jager would like to see a few more options available with the system. “For example, having an OCT overlay would be helpful,” he notes. “Right now we’re using our Heidelberg Spectralis to look at OCT scans; we then combine that data with the angiogram to decide exactly where to laser. Also, the company is planning a wide-field PRP module which is not available yet. That would be a useful addition.”
For more information about the Navilas system, call 1 (877) 628-6367 or visit od-os.com.