FOCUS ON …
Patient-tailored Retina Treatments Could Improve Safety and Predictability
LESLIE GOLDBERG, ASSOCIATE EDITOR
Among the recent advances in laser technology, one stand-out is the Navilas laser system (OD-OS, Teltow, Germany), which allows physicians to place a registered overlay of a patient's diagnostic image and surgical plan onto the retina during treatment.
"The Navilas laser system is a scanning slit ophthalmoscope capable of capturing infra-red, red-free and color fundus imaging as well as performing fluorescein angiograms, giving the surgeon images to directly design his/her treatment plan which will then be overlaid on the live fundus view. The system will pre-register these treatment locations including spot size and pulse width and follow the patient's eye movements in a serial delivery controlled by the surgeon.," explains William R. Freeman, MD, director of the University of California-San Diego's Jacobs Retina Center, one of the clinical investigators for the device. Navilas received FDA approval in late 2009.
The system combines image capture technology, surgical planning software and an integrated 532-nm DPSS treatment laser. Physicians view the angiogram on a PC screen and decide, based on the clinical situation and the angiographic leakage, which areas to treat.
A UNIQUE TREATMENT PROTOCOL
"What is unique about this system is that, after you decide where you want to treat, you can do your treatment planning on top of your patient's angiogram, color or red-free photograph," says Dr. Freeman. "I can highlight microaneurysms, areas of edema and diffuse leakage. I can also look out into the periphery of the retina and see if the patient needs limited panretinal photocoagulation." After the angiogram is taken, physicians are then able to treat the patient immediately or schedule the treatment for a later date, as the system stores digital documentation of treatment plans. The documentation feature is also useful if there's a need for retreatment in the future.
"I look at my patient's angiogram, decide exactly where I want the treatments done, and highlight those areas. When I bring the patient back for treatment and put him or her in front of the fundus camera again, the machine takes the patient's treatment plan and overlays the angiogram on top of the live fundus image," using its image registration and stabilizing technology, says Dr. Freeman.
Figure 1. Planned and marked microaneurysms as well as marked areas not to treat are overlaid and stabilized onto the living patient fundus, which is being comfortably imaged in infrared light. The laser-aiming beam has locked on to the first microaneurysm seen at 2:30 o'clock near the optic nerve head.
Figure 2. Fundus photograph after treatment shows precise localization of burns at areas of microaneurysms or targeted areas.
The areas that are to be treated appear as small white circles on top of the patient's live fundus image. If the eye moves, the planned position and aiming beam stays with it. If the patient closes the eye or the image is not overlaid correctly, the system will not treat. This is called registered imaging and treatment. "The laser is really semiautomatic. You have already planned yourself or with the photographer where you want to treat. That treatment plan is overlaid onto the patient's retina, and the laser beam auto advances to the first and subsequent points to treat. You see an aiming beam on top of your first point on the retina," says Dr. Freeman. Once the doctor confirms that that point is correct, he or she hits the pedal, and that area is treated and the laser moves to the next mark. It will beep once it locks onto the next target. The physician, however, fully controls the application of each laser pulse.
ADVANTAGES OF THE NAVILAS
Dr. Freeman says this system has many advantages. With this system, doctors don't have to look at an angiogram on a different monitor and then look back at the eye and guess if they are treating the same aneurysm. "The angiogram is overlaid on to the actual patient's eye when you are treating them. Though it does provide many preset laser patterns, "most doctors will want to choose the areas they want treated," Dr. Freeman says. Its strength is in the ability to tailor the application of pulses, and mark areas that should not be treated. "If you want to do panretinal photocoagulation, you can, while avoiding certain areas of the retina.
He says another advantage is elimination of slit-lamp visualization, which causes reflections and limits the field of view. "You are able to see the entire retina and it can be imaged in infrared mode, so you see a black-and-white image," says Dr. Freeman. "The patient is comfortable be cause a bright lamp is not being shone in his or her eye the entire time. The device now has incorporated a treatment verification switch so you can toggle to a color fundus view to verify treatment uptake." He says this helps doctors see the intensity of the burn. Doctors can then titrate the laser power based on lesion burns.
In addition, doctors don't always need to use a contact lens for this treatment. This is an advantage because nothing is touching the patient's eye during treatment and the doctor has two hands available during the procedure. RP
|William R. Freeman, MD, is professor and director of the Jacobs Retina Center at the UCSD Shiley Eye Center in La Jolla, CA. He is a consultant for OD-OS and works with Heidelberg, Canon and other imaging companies as well.|