Retina Today - GLOBAL PERSPECTIVES: Experience With Modern Vitrectomy Machines (January/February 2012)

摘要

Aretina specialista??s surgical outcomes depend mainly on his or her experience, knowledge, and ability. However, results can also be affected by the performance of his or her vitrectomy machine. Additionally, if one has an academic position in a teaching hospital, extra care must be taken with every patient when helping a fellow in his or her surgery (especially at the beginning of the academic year). Therefore, knowing how to control the fluidics of his or her preferred vitrectomy system must be a priority for every posterior segment surgeon. At the Association to Prevent Blindness (Asociaci?3n Para Evitar la Ceguera en M??xico [APEC]), an ophthalmology referral center in Mexico City, the Accurus Surgical System (Alcon Laboratories Inc.) was the leading vitrectomy machine for at least 6 years. Therefore, most vitreoretinal surgical guidelines at the center had been dictated by venturi- controlled vitrectomy systems. However, vitreoretinal surgery has evolved greatly over the past 4 decades, not only with improvements in vitrectomy machines and fluidics, but also with new and safer endoilluminators, better visualization and optics from the microscopes, and adjuvants such as heavy liquids and stains. Over the years, a decreasing rate of transsurgical iatrogenic complications has been observed in our department, most likely due to these improvements. It is important to keep in mind that, in Mexico, the main indications for vitrectomy are diabetes-related complications. Of these, tractional retinal detachments can be particularly complex, so the attending (and often the fellow) should be proficient in avoiding excessive traction that could lead to additional complications. Now there are new options for vitreoretinal surgery. Vitrectomy machines such as the Constellation Vision System (Alcon Laboratories Inc.) and the OS3 (Oertli Instrumente AG) provide different capabilities that allow faster and better cutting and fluidic action during surgery (and hopefully yield fewer iatrogenic retinal tears). This article explores some of the advantages and disadvantages of each system. PUMPS AND FLUIDICS Two types of pumps are availablea??peristaltic and venturi. Peristaltic pumps are positive displacement machines. The fluid contained within a tube is forced to move within the system by rollers that compress it. Venturi pumps operate based on the principle of the same name, in which pressure is reduced when fluid flows through a constricted section of a pipe, thereby providing instant negative pressure.1 Fluidic control in the Constellation Vision System works by means of a venturi pump that can control the aspiration rate, with a maximum vacuum of 650 mm Hg. This works in a similar manner as a peristaltic pump. Hence the surgeon has control over the aspiration and the vacuum force induced on the vitreous humor. One key advantage of the Constellation system is the IOP control; even if high aspiration/ vacuum is required, the system automatically compensates the infusion pressure. Therefore, one is expected to experience fewer hypotony-related complications. Duty cycle is the percentage of time that the port probe is open divided by the duration of the entire cycle.2 Duty cycle modification, available with the Constellation system, helps the surgeon achieve a more efficient performance when shaving or performing core vitrectomy. However, it is rarely necessary to modify this parameter because the presets work perfectly. The OS3 offers different capabilities. This vitrectomy machine has both venturi and peristaltic pumps that can achieve a maximum vacuum of 600 mm Hg and a maximum aspiration of 50 mL/minute. The surgeon can choose between the 2 pump systems by simply pressing a button; therefore; it is up to the retina specialist to define which pump and parameters he or she will use depending on whether core vitrectomy or vitreous-base shaving is being performed. In o