Article Date: 1/1/2011

Novel Illumination With an Eye on the Future

Novel Illumination With an Eye on the Future

Stellaris PC offers versatility and excellent visualization with the potential for increased safety.

By Suber S. Huang, MD, MBA

Successful vitreoretinal surgery depends on many perfectly executed steps. The ability to optimally visualize the tissue is critical to fully utilize new and emerging vitreoretinal techniques. To that end, Bausch + Lomb has developed a unique illumination system for its recently introduced Stellaris PC combined posterior vitrectomy and phacoemulsification surgical platform. Here, I explain several of the novel features that set it apart from what we are accustomed to using.

VERSATILITY

One aspect of illumination for vitrectomy that has been noticeably lacking is versatility, particularly in terms of the wavelengths used. We have only recently begun to appreciate how a number of different lighting options exist, and that they may have some differential advantages. Additionally, some systems are limited to one illumination port. The Stellaris PC brings us improvement on both of these fronts. The system has two different illumination sources. One provides the efficient luminosity of a mercury vapor lamp. The other provides the broad spectrum white light of a xenon lamp. These are dual independent lamps, which can be used simultaneously or as backups. Furthermore, because the system is open-architecture, chandelier lighting systems, illuminated infusion cannulas and illuminated instruments can be used in combination to optimize visualization.

This new system also includes three filters: amber, green and yellow. As one considers different concepts of advanced visualization, surgeons can actually begin to explore whether different wavelengths provide a more efficient, safer or more effective means of visualizing the retina. This option has not been available in the past, and it is a promising feature of this new technology.

All of the filters can be controlled by the surgeon in the operating room and changed during the case as the pathology dictates. Five different light scenarios, adjustable to our needs, are available. Lighting intensity can be precisely controlled and easily adjusted. The ability to use different wavelengths and filters in various combinations gives us versatility that may be very useful as vitreoretinal technique and instrumentation continue to evolve.

Ideally, an illumination system should be easy to use, and that is another positive aspect of the Stellaris PC. For example, both lamps can be replaced without tools. Also, all gauges of Stellaris PC fibers use the same fiber size. Therefore, all gauges deliver the same amount of light.

FILTERED LIGHT AND INCREASED SAFETY

Light matters when it comes to vitreoretinal surgery. In many ways, a lecture hall is very much like the inside of the eye. We illuminate where the action is taking place, but the type and intensity of lighting in the other parts of the hall are equally important to consider. Thanks to David Chow, MD, FRCSC, and others who have pioneered research, a great deal has been learned about how light can affect the eye both in a hazardous fashion and in a beneficial fashion. The lighting system of the Stellaris PC was developed from the “ground up” with specific attention to the fundamental and functional aspects of the eye's photopic response in order to develop useful, safe and versatile illumination.

Light is quantified in lumens, the sum of all wavelengths in the spectrum (the range of color by wavelength) weighted by the sensitivity of the surgeon's eye under surgical conditions. The standard light system delivers approximately 10 lumens at 100% power. The Stellaris PC light options can produce significantly more light. At 100%, the xenon puts out 30 lumens, the amber 15, the green 24, the yellow 27 and the mercury vapor 30. Therefore, the Stellaris PC has reserves of illumination that can be called upon when needed. This allows us to look to the future and consider some very novel thoughts and concepts.

The concept of hazard watts is important for safety and is calculated as the sum of all wavelengths in the spectrum weighted by the sensitivity of the patient's eye to photochemical reaction. At 100% illumination with the Stellaris PC, this value ranges from 0.0001 to 0.0117 hazard watts. The lumens per hazard watt is the inverse of the hazard watt value. Under certain circumstances, we can obtain much more intensity and still have a perfectly safe spectrum. For example, with the amber filter using xenon, we have lumens per hazard watt of 157,885, which is approximately seven and a half times safer than xenon white light at the same intensity (Figure 1). This demonstrates the ability to reduce the hazard for our patients while maximizing the most efficient wavelength for our visualization. The ability to continuously optimize illumination should help to make surgery easier and safer for patients.

Figure 1. The illumination system for the Stellaris PC was designed under the concept that it is possible to reduce the hazards of light exposure for patients while maximizing the surgeon's visualization.

Filtered light helps increase safety because it shifts the wavelength away from the more damaging effects of the blue light spectrum (Figure 2). Another way to enhance safety is to use light efficiently. With the Stellaris PC mercury vapor lamp, the spectral output peaks so that there is less light delivered from undesired wavelengths (Figure 3). This has beneficial secondary mechanical effects, such as avoiding heat, while providing that light only in the spectrum that we appreciate.

Figure 2. Filtered light helps to increase safety because it shifts the wavelength away from damaging blue light.

Figure 3. Efficient use of light, as seen here with the Stellaris PC mercury vapor lamp, is one way to enhance safety.

EXCELLENT VISUALIZATION

Regarding illumination for vitreoretinal surgery, we often ask the same question as we do with cutting speed: How much is enough? Using the Stellaris PC lighting system, there is excellent illumination of the ocular structures, even at 20% of capacity of the available wavelengths (Figure 4). At 20%, the optic nerve, macula and the vessels are well visualized. Typically I operate with light settings at 40% to 50% of capacity and I tend to vary the light filter depending on the specific step of the procedure. Moderate amber light provides good illumination for a core vitrectomy and inducing a posterior vitreous detachment. Green or yellow illumination assists in macular membrane peeling while offering an enhanced safety profile. Bright white light is seldom used but has helped in some cases of severe proliferative vitreoretinopathy. I have not found the need for 100% capacity with any light filter, but it is comforting to know that sufficient capacity exists should the clinical situation arise.

Figure 4. The various wavelengths available with the Stellaris PC imaged in the same patient at intensities from 20% to 100% and the resulting surgeon views.

FOSTERING SAFE, UNCOMPLICATED SURGERY

The illumination capabilities of the Stellaris PC provide multiple advantages. Not all cases require a single light source. At times, such as when we're doing bimanual surgery or working in the periphery, our lighting needs change. This new system provides enhanced and welcomed versatility. Just as importantly, the system is safe. Utilizing multiple wavelengths, even within a case, may better protect the retina from phototoxicity. Finally, the system is flexible. Because we have the same fiber size for all gauge instruments, the amount of light is the same across all wavelengths and provides reproducible and reliable surgical experience.

When we put all of the features together, an advanced visualization system helps us identify pathologic tissue, the internal limiting membrane and the vitreoretinal interface, crucial steps for achieving successful and uncomplicated surgery.


Dr. Huang is director of the Center for Retina and Macular Disease at the University Hospitals Eye Institute at University Hospitals Case Medical Center in Cleveland, Ohio, and is a the Philip and Elizabeth Searle Professor and Vice-Chair at the Case Western Reserve University School of Medicine.

Stellaris PC Q&A
Q: For those of us who use indocyanine green for staining the ILM, is it possible that using the different wavelengths available on the Stellaris PC theoretically might be beneficial in avoiding phototoxicity?
Dr. Huang: The reports of toxicity from ICG certainly haven't gone away, and I think certain patients are particularly susceptible. Of course, there are many components to the equation, such as how fast the surgery goes, the concentration of ICG and how thick it is. That said, using different wavelengths may help. With this particular system, although it's still theoretical at this time, the data suggests that using the amber wavelength could be safer.


Retinal Physician, Issue: January 2011