Article Date: 11/1/2008

Improved Illumination and Visualization

Improved Illumination and Visualization

Learn how new technology eliminates the darkness of the past.

Dr. Chang: Let's move on to the subject of illumination and visualization. Optimal lighting, proper light fiber selection and the use of visualization aids, such as triamcinolone, have become even more critical in the transition to 25-gauge and 23-gauge options. Dr. McCuen, what role does the high brightness illumination play in your procedures and what lighting are you using?

I think the evolution in lighting in vitreous surgery has really been the cornerstone of most of the other advances that we have seen. I do not think micro-incision vitreous surgery would be viable if we did not have much better illumination than we had 10 years ago.

Brooks McCuen, MD

Dr. McCuen: I think the evolution in lighting in vitreous surgery really has been the cornerstone of most of the other advances that we have seen. I do not think micro-incision vitreous surgery would be viable if we did not have much better illumination than we had 10 years ago. In the past, we always had to turn the lighting up to the maximum level, and it seemed to never be enough.

But now, for the first time, you do not need maximum illumination, because the sources are so good. I compare this technology to driving an automobile. The automobile may be capable of hitting 150 mph, but that does not mean I have to drive it 150 mph. However, if I have a specific situation in which I want to increase the speed, I can.

It is the same with our illumination systems today. You can increase the illumination if you are in a difficult situation, but you do not need it at the maximum level all of the time. I think the lighting systems have been critically important in terms of improving our ability to deal with sophisticated vitreoretinal surgery.1

Dr. Charles: New engineering has helped significantly in this area. The numerical aperture of the light source has been matched to that of the fibers. The fiber terminations have been improved, resulting in a more efficient system that requires a less intense light source to produce the needed intensity at the endoilluminator. I have used the Constellation clinically and have needed to turn down the light to settings of 15%-25% when doing macular surgery.

Because radio frequency identification (RFID) is embedded in the probes, the probes identify themselves to the system, which automatically adjust the light intensity to a safe level. If you forget to reduce the setting when you move from a case that requires a good deal of light, such as a 25-gauge vitrectomy for dense vitreous hemorrhage in a patient with a darkly pigmented fundus, to a case that requires substantially less light, such as a 20-gauge macular surgery patient, the system will normalize to a safe light output, adjusted for tool light throughput, divergence angle and typical working distance, greatly reducing the chances of light toxicity.

Dr. Corcostegui: I think the tendency is for surgeons to use both light and the forceps at the same distance in the eye and, many times, very close to the macula. This kind of strong light can be dangerous. I train my Fellows to work at different distances. I put the light far away from the retina and have the forceps working over the retina. So, we have much less light on the retina. I think it is good practice to work asymmetrically with the instruments. At the beginning, it is a little difficult, but it is a much better approach.

Dr. Chang: I agree with you, Dr. Charles. The Engauge RFID is a really good safety feature. It keeps the light down in the 20-gauge cases. Our problems have been associated with not recognizing that 20-gauge instruments are being used and not turning down the light in those situations.

Dr. Packo: It is a new learning challenge for Fellows. You mentioned the analogy of cars, Dr. McCuen. I don't know what it was like to drive a Model T. People get into a modern car now and take so much of the technology for granted. We know we can go fast with it but we have no personal memory of driving a Model T when the top speed was 40 mph.

I do remember, however, what it was like to put the Occutome light probes together, with all of the breaks in fiber optic lines, and have lighting that was dismal. It was the Model T of vitrectomy instrumentation. For 20 years, we complained about the dismal lighting, and now, for the first time, we have great lighting. The retinal Fellows that are training now are living in an era when they start with great lighting and they must be cautioned that you can have too much of a good thing. Thankfully, we have technology with RFID that, again, lets the machine think for us a little, keeps us out of trouble and helps us avoid damaging the eye.

INTRAVITREAL TRIAMCINOLONE

Dr. Chang: Dr. Flynn, you mentioned that you are using intravitreal triamcinolone more often during surgery. Could you explain when you find it helpful?

Dr. Flynn: I like the concept of intravitreal triamcinolone dispersion over the posterior pole. You can identify the cortical vitreous and make sure you are not leaving any residual vitreous. But I mainly make this choice so that I can identify cortical vitreous and preretinal membranes when I am not able to do that with other techniques. This is a fair percentage of my cases.

Dr. Chang: Professor Tano, triamcinolone is used much more readily in Japan. Could you talk about your indications for using it?

Professor Tano: When we treat proliferative diabetic retinopathy (PDR) cases, I think we should apply the triamcinolone acetonide to the eye so that we can identify the very thin film of the vitreous cortex adhering to the unexpectedly large area of the posterior fundus.

The other area where I find triamcinolone to be quite useful is in a teaching setting. I let the Fellows do the vitrectomy … Then we put the triamcinolone in, and it can be a very humbling experience. But it also teaches them the importance of a complete vitrectomy.

George A. Williams, MD

Dr. Williams: I agree with Professor Tano. The other area where I find triamcinolone to be quite useful is in a teaching setting. I use it to demonstrate to Fellows early on in their training just how much they are leaving behind, and the little things that need to be done in order to optimize vitreous visualization. So I often will let the Fellows do the vitrectomy and let them think that they have done a pretty good job. Then we put the triamcinolone in, and it can be a very humbling experience. But it also teaches them the importance of a complete vitrectomy. I find it to be a very useful teaching tool.

Dr. McCuen: In addition, in terms of teaching, it really demonstrates to the Fellow the anatomy, especially in macular holes and vitreo-macular traction. They may know that the vitreous is attached back there, but once you put the triamcinolone in, the anatomy becomes crystal clear. I think they really get a better understanding of it.

Dr. Flynn: There's one other area — uveitis. If you have a younger patient with pars planitis or juvenile idiopathic arthritis, the patient usually has an adherent posterior cortical vitreous that is difficult to remove. The triamcinolone acetonide allows you to see what is left behind after the core vitrectomy. With triamcinolone, you can easily identify vitreous in the posterior pole and be more confident that you have removed the cortical layer. RP



Retinal Physician, Issue: November 2008