The CONSTELLATION® Vision System: Assessing the Improvements in Illumination for Vitreoretinal Surgery
ROGER L. NOVACK, MD, PhD
The CONSTELLATION® Vision System (Alcon, Fort Worth, Texas) can be reasonably characterized as the first in a new generation of tools for vitreoretinal surgery. Of the numerous innovations incorporated into the system, the advances in illumination are significant. Changes in the design of the illumination source and improvements in light fiber design combined with the efficiency and ease of use provided by ENGAUGE® RFID Technology deserve attention. These changes are designed to provide brightness and color to enhance visualization, and in my opinion, a substantial improvement in intraoperative efficiency.
The CONSTELLATION® Vision System replaces Alcon's previous instrument, the ACCURUS® Vitrectomy System, which provides an appropriate comparator to understand many of the newer system's innovations. The other contemporary integrated system for vitreoretinal surgery is the MILLENNIUM® (Bausch & Lomb, Rochester, NY).
By themselves, each of the specific properties of the CONSTELLATION® Vision System's illumination system has the potential make a unique contribution to the potential for improved outcomes. However, it is important to consider them within the context of the other features of the system to fully appreciate the sum of the parts.
|Roger L. Novack, MD, PhD, who is affiliated with Retina Vitreous Associates Medical Group in Los Angeles, California, has a BS in electrical engineering, an MS in biomedical engineering, a PhD in physiology and biophysics, and an MD. He has collaborated on the development of several devices for retinal surgery. Dr. Novack is a consultant for Alcon Laboratories, Inc., Fort Worth, Texas.|
NOVEL OPTICS DESIGN
The CONSTELLATION® Vision System features innovations in optics design that have far-reaching implications for enhancing output performance. These innovations relate to the quality of light over the course of bulb life and the properties of the light emission.
The system uses a filtered xenon bulb with an emission wavelength that reduces blue light content compared to previously available light sources. For most applications, the reduction in the blue portion of the spectrum more closely approaches the colorless illumination that most surgeons recognize as providing optimal visual quality. At the time of their introduction, the MILLENNIUM® metal halide and the ACCURUS® halogen illuminators provided incremental light intensity improvements. Initial xenon illuminator designs surpassed those earlier advances. Now, the latest xenon illuminator technology in the CONSTELLATION® system provides an additional step towards optimum color characteristics and light intensity, thereby enhancing visualization during vitreoretinal surgery.
The new optical design used in the CONSTELLATION® Vision System provides longer bulb life than the ACCURUS® AHBI. Longer bulb life could deliver several advantages, including a reduction in the cost and inconvenience of bulb replacement. Also important, the quality of light has been engineered to remain more consistent with significantly less degradation over the first 200 hours. After 200 hours, gradual degradation begins, but even at the end of bulb life the light level remains well above that of the current ACCURUS® halogen bulb. The dependably stable light intensity during the first half of the bulb's life avoids the insidious reduction in light quality that has been a liability with previous xenon models, an advantage that has the potential to preserve surgical efficiency over the life of the bulb.
The CONSTELLATION® system is available with 4 illumination ports powered by 2 separate illumination sources (Figure 1). Although the system stipulates that no more than 2 ports be employed at a given time, the additional ports allow the surgeon to attach up to 4 instruments to the device so that they are available for use without switching plugs, but by simply pushing a button. Rather than light delivery with a beam splitter, which can degrade light transmission, the CONSTELLATION® employs a dual mirror system that delivers light through each of the 2 ports in use. The sophistication of the mirror system is a major step forward in ensuring optimal light intensity. The position of the lamp at the center of the symmetrical two channel optical design delivers identical light intensity through each of the 2 ports.
Figure 1. The CONSTELLATION® Vision System includes 4 illumination ports.
ADVANCED PROBE TECHNOLOGY
The surgical probes for the CONSTELLATION® Vision System also present innovation in technology. Each probe is equipped with ENGAUGE® radio frequency identification (RFID) connector technology so that it is immediately recognized by the system when attached. The RFID tag recognizes gauge size and probe type and then adjusts light intensity for that specific probe to a preset default level (8-10 lumens at the tip). This "plug and play" feature is especially useful for nurses or technicians who are responsible for preparing the system for use. It not only may save time but could prevent some common mistakes.
Light indicators guide the connection process. During the set-up process, when the light fiber icon is selected, ring illumination will guide probe connections and the user interface can display the amount of bulb life remaining.
The longer-lasting xenon bulb is time checked and provides total lamp hour and colored indicator ring feedback on lamp life:
- Green = 0 to 200 hours
- Yellow = 201 to 400 hours
- Orange = 401 to 800 hours
The new generation of hand-held illumination probes includes straight, bullet and wide-angle fibers which permit the surgeon to employ a light source that is optimal for the task. For example, a straight probe may be preferable for peeling a membrane off the retina, while a wide-angle probe may be more useful when applying laser photocoagulation in the peripheral retina. One of the probes that I have utilized, the sapphire wide-angle illumination probe, provides a 106° angle that reduces glare and provides even illumination across the light cone. It is important to note that glare has been an obstacle to effective use of wide-angle probes in the past.
The design of the probes, together with the symmetrical design of the light source, mitigates some of the loss of light that occurs. While probe diameters smaller than 20-gauge are preferred because they often reduce the need for sutures at the end of the surgery, the loss of light with smaller gauge sizes demands more light from the illuminator source to compensate. For example, a typical 25-gauge fiberoptic is half the size of a 20-gauge fiberoptic, and the associated light output is reduced by 60%. (from 10-12 lumens down to 4-5 lumens). The illuminator source needs to be 60% brighter to get back to par. Also, the CONSTELLATION® system's endoilluminator probes employ a 20-gauge fiberoptic from the connection at the light source to the probe handle at which the fiber narrows to fit into the smaller gauge needle. This improves the probe's light transmission performance and ultimately the light intensity output performance.
EMPHASIS ON MEANINGFUL SURGICAL BENEFIT
I believe the most important characteristic of the illumination source created for the CONSTELLATION® system is its versatility. Although the improvements in the light source and probe fiber design deserve attention, there are many additional features of the system that evolved from a close collaboration between surgeons and engineers who sought to translate each technological advance into a meaningful surgical or efficiency advantage. The end result is a meaningful upgrade that addresses many of the inconveniences and weaknesses of current devices.
The illumination in the new CONSTELLATION® Vision System is part of a comprehensive overhaul of the approach to vitreoretinal surgical management, one that represents a substantial advance over previous technology. The system defines a new standard against which other new-generation devices will be compared. The CONSTELLATION® Vision System's illuminator delivers bright, white xenon light to the maximum levels allowed under current irradiance limits, consistent light output over the 1st 200 hours and the ability of the machine to accurately sense the probe and preset the intensity of the light. This output makes the CONSTELLATION® unique among available systems. It is difficult to compare one system to another on the basis of objectively measured outcomes, but many of the key components of the CONSTELLATION® system would be expected to aid the surgeon in patient management. RP