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Fine Control for Pediatric Retina Surgery
The CONSTELLATION Vision System's features help surgeons optimize outcomes.
By Kimberly Drenser, MD, PhD

The majority of the pediatric retina surgical cases that I see at Associated Retina Consultants in Royal Oak, MI, are retinopathy of prematurity (ROP) that require vitrectomy for retinal detachment. I have recently begun to use the CONSTELLATION Vision System (Alcon Laboratories, Inc.) and have found some important advantages to this system that I can apply to surgical outcomes for my patients.

DIFFERENCES IN OCULAR ANATOMY
When performing a vitrectomy on a child, especially an infant, there are a few significant differences in anatomy that must be taken into consideration. The most obvious difference is the size of the eye, which will of course be smaller in an infant, providing less room to maneuver surgically. Additionally, the eye is not fully developed in retinopathy of prematurity (ROP); these infants do not have a true pars plana, so the entry site for vitrectomy has to be modified.

Perhaps one of the more significant differences between surgery in pediatric and adult vitreoretinal surgery is the allowable margin of error. In an adult eye, there is a large margin; if a retinal break occurs or the surgeon inadvertently takes a bite out of the retina, it may extend the case, but the situation is not irreparable. In a pediatric case, similar situations often are case-enders. As a result, surgeons tend to be less aggressive in pediatric cases; for instance, one might not shave as close or dissect as aggressively.

FINE CONTROL IMPROVEMENTS
The control that I have over fluid dynamics represents one of the areas where I find the biggest advantage with the CONSTELLATION Vision System over other systems that I have used. It offers me fine fluidic control when working over the retina. With reduction of the surge into the port I can be more aggressive in these pediatric cases, while maintaining what I consider to be a safer procedure.

Other features on the CONSTELLATION System that provide a higher degree of fine control are duty cycles, higher ranges of cut rates to vacuum, and intraocular pressure (IOP) control.

I also find a nice benefit to having the fluid-air exchange on the machine rather than on the stopcock. This feature reduces the margin for error because it is more intuitive to be able to switch from one to the other directly on the machine. Additionally, both the air and fluid chambers internal to the machine maintain pressure independent of one another, allowing independent control of fluid and air pressure.

Illumination is more important in pediatric surgery. We use a two-port vitrectomy system with illuminated infusion, which greatly decreases the amount of illumination coming through. Having the xenon light source is helpful to sharpen duller visualization in these cases.

CLINICAL CASES
Recently, I had a patient with persistent fetal vascular syndrome on whom I performed a vitrectomy for ROP detachment. Because of the duty cycle control and the fluidics on the CONSTELLATION System, I was able to vitrectomize a very dense plaque (Figures 1 and 2) that in ordinary situations, we would never be able to remove with a vitrector. In my opinion, duty cycle made a tremendous difference. Another case in which I used the CONSTELLATION System was an infant with a total retinal detachment with a great deal of bullous retina and an abnormal vitreous insertion. Because of the duty cycle control, fluidics and higher cut speeds, we were able to closely shave the vitreous base and dissect some of the areas of attachments safely—without having the bullous retina hinder the procedure. In this case, we did not have to use any perfluorocarbon to flatten or control the eye; rather, we were able to perform the entire procedure under fluid, which is a testament to the IOP Control and the fluidic stability of the system.

SUMMARY
I am still becoming accustomed to features on the CONSTELLATION System as I gain more experience with it. The features mentioned here have impressed me the most and I am looking forward to working with this machine for more of my patients.

Kimberly Drenser, MD, PhD, is with Associated Retinal Consultants in Royal Oak, MI. She reports that she has no financial relationships to disclose related to this article. She can be reached via e-mail at kimber@pol.net.