VITREORETINAL SURGERY
Insights

Advances in Endoillumination for Microincision Vitreoretinal Surgery

By Colin A. McCannel, MD, Jules Stein Eye Institute, Los Angeles, CA, USA

With the evolution of minimally invasive small-gauge vitrectomy, higher light intensity illumination sources became necessary, both to compensate for the reduced transmission through smaller gauge instruments and for broader diffusion of light associated with chandelier-type illumination. More powerful illumination options include metal halide, xenon, mercury vapor and light-emitting diode (LED) technology. Light sources can cause retinal photochemical toxicity and vision loss; on the other hand, they must deliver sufficient light for optimal tissue visualization. Therefore, safety and intensity are central considerations in determining the optimal light source device for endoillumination in vitreoretinal surgery.

Top features: safety, light intensity and versatility

The three most important features of the LEDStar endoillumination system for the clinician are its safety, brightness and versatility. There is a very high power threshold before there is any potential light toxicity, shown clearly in the LEDStar spectral output curves. Light exposure during vitreous surgery can induce photochemical damage to the retina, the hazard of light radiation from endoilluminator light sources increasing with decreasing wavelengths. When we compared the spectral output distribution pattern of LEDStar with the light sensitivity of the eye, we observed a high degree of overlap, perhaps best among all of the light sources available today. As a result, the light color produced is extremely comfortable for the human eye and for the surgeon.

Usage of the high light intensity of the LEDStar in routine cases of 23- or 25-gauge lightpipe endoilluminators requires only a portion of the potential output. There is far more light available for use in complex or challenging cases to achieve proper illumination required at the level of the retina where one is working. Also, there is plenty of reserve intensity for 27-gauge lightpipe endoilluminators and chandeliers to easily deliver sufficient light for optimal surgical visualization. For 27-gauge vitrectomy surgery, ultra-thin fiber optics are utilized; it can take a lot of ‘push’ to obtain sufficient light delivery into the eye. However, the high light intensity setting of the LEDStar delivers more than adequate illumination to the eye for differentiation of tissues during microincision vitrectomy.

Excellent tissue visualization

Additionally, color or light ‘temperature’ can be adjusted to suit surgeon preference and experience, as well as to further enhance safety. Individual surgeons will experiment to identify the light temperature that they are most comfortable working with, configure the settings and then use a consistent setup for the majority of cases. For me, when I use LEDStar, I have settled on a setting of 10 (range is 1-20) as my preferred light temperature: it produces a nice white color with only faintly yellow tint light that is safe and the tissue visualization is excellent.

A further consideration in choice of light source technology is durability and robustness. The LED technology is inherently highly durable with three independent light channels with an estimated expected life span of at least 10,000 hours each. Therefore, light failure from bulb burnout is virtually impossible or non-existent. Moreover, there is no decline in output due to light bulb aging, and no annual or semi-annual bulb replacements are necessary. Light-emitting diode illumination technology is also robust.

CIE 1931 x.y chromaticity diagram
The surgeon can control the LEDStar illumination color from white to yellow along the intensity of the light to suit preference and experience. Source: DORC International

Incremental improvements for better overall surgery

It’s fair to say that the LEDStar illumination system matches or indeed exceeds my visualization expectations and needs as a vitreoretinal surgeon. Other illumination systems such as xenon and mercury vapor light sources are adequate, but we are at the stage in vitrectomy surgery technology where incremental improvements mean easier and therefore safer procedures. Thus, adequate is not sufficient, we want to benefit from improvements in ease of use, and the more comfortable the surgical environment, the less likely it is you are going to encounter problems. It’s easier and simpler to do things well with these incremental improvements, all of which are inching us toward better and more effective surgery, which means fewer complications that might lead to poor vision outcomes.

Effect of lamp aging on light output - 23G fiber
Effect of lamp aging on light output: LEDStar endoillumination provides constant output. Source: DORC International

Looking back at the recent history of small-gauge surgery, there is evidence of overall improvements. For example, it is well documented in the literature that there are significantly fewer peripheral retinal tears with 23- and 25-gauge surgery compared to 20-gauge surgery. Similarly, with modern high-output LED light sources, I expect to see better surgery due to enhanced visualization without increased risk.

Enhanced visualization can facilitate membrane and ILM peeling and reduce the dependence on staining with vital dyes, or at least allow for minimizing the intensity of staining. Chandelier lighting is commonly used during bimanual surgery, for example while operating on difficult diabetic tractional retinal detachment cases or proliferative vitreoretinopathy retinal detachments. More powerful light sources such as LEDStar now facilitate effective chandelier illumination through 25-gauge and 27-gauge fiber optic instruments, and will allow many surgeons that were dissatisfied with chandelier illumination systems in the past to gain newfound confidence and surgical flexibility.

Now, with growing acceptance of 27-gauge surgery, you need even brighter light. I have used 27-gauge surgery with the LEDStar light source, and the surgical experience is outstanding, with very good tissue visualization throughout the surgical field as a result of the available intensity. When performing 23- and 25-gauge vitrectomy, I typically operate at between 40% to 50% of available light intensity output for optimal tissue identification. This is turned up to 60-70% intensity for 27-gauge vitrectomy, leaving plenty of light to tap in to for illuminating unusually darkly pigmented eyes and other situations when extra light may be needed. ■