The Surgery Guidance 3000 (SG3000; SensoMotoric Instruments; Figure 1) is a novel eye-tracking device that may be used to implant toric IOLs without the use of manual ink-marker steps. The SG3000 system consists of two units: the reference unit, used to measure the patient preoperatively, and the surgery pilot, which is positioned in the operating room. The reference unit is a noncontact device that acquires a high-resolution digital image of the eye, in which the limbal vessels, scleral vessels, and iris characteristics are shown in detail (Figure 2). Simultaneously, this unit performs keratometry, and these results—including the steep and flat meridians of corneal astigmatism—and the position and diameter of the limbus and pupil are shown in an overlay in a digital image (Figure 2).
When the patient arrives in the operating room, the preoperative image from the reference unit is loaded into the surgery pilot, which consists of a PC, a microscope camera adaptor, and a microscope-integrated display. Next, the incision location and size, the capsulorrhexis location and size, and the implantation axis of the toric IOL are configured. The live image from the operating microscope is then matched with the preoperative digital image, based on blood vessel and iris characteristics. Intraoperatively, an overlay is visible in the operating microscope showing the intended incision location, capsulorrhexis, or IOL alignment axis (Figure 3). The SG3000 system uses eye-tracking technology based on limbal and scleral blood vessels and iris characteristics to correct for all rotational and translational movements of the eye during surgery.
We have been using the SG3000 system in our department for approximately 2 years. In our experience, it is an easy-to-use system that increases the accuracy of toric IOL alignment. We perform the preoperative measurement using the reference unit with the patient’s eye in mydriasis because, in our experience, this provides the best match with the live image in the operating microscope. During surgery, we found that the system is stable and tolerant to zoom, light changes, and other surgery interactions. As shown in Figure 3, alignment of the toric IOL using the overlay in the operating microscope is fairly easy to do. This prevents problems that may occur with manual ink markings, such as wash-out or fading of ink marks, and increases the accuracy of toric IOL alignment. 1 Another advantage of the SG3000 is that the size of the overlay diagram matches well with the size of the IOL marks, whereas ink marks are usually much larger.
In addition to toric IOL alignment, we use the SG3000 system for other applications in lens implantation surgery. First, it provides an extra safety check, as it allows the surgeon to ensure that the correct eye of the correct patient is being operated on. Second, we use the SG3000 to plan the location of the main incision and paracenteses. Because the preoperative keratometry results are visible, it is possible to directly position the main incision on the steep axis of the cornea. Third, the SG3000 may be used to choose an exact capsulorrhexis diameter. Fourth, when implanting a multifocal IOL, the system helps to center the IOL according to the location of the undilated pupil.
Overall, the SG3000 system provides a simple and accurate method for toric IOL alignment. Additionally, this system may be used for other aspects of lens implantation surgery, including incision location, capsulorrhexis, and IOL centration.
Rudy M.M.A. Nuijts, MD, PhD, is an Associate Professor of Ophthalmology in the Department of Ophthalmology at the Academic Hospital Maastricht, Netherlands. He is a member of the CRST Europe Editorial Board. Dr. Nuijts states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +31 43 3877343; e-mail firstname.lastname@example.org.
Nienke Visser, MD, is a doctoral (PhD) student in the Department of Ophthalmology at the Academic Hospital, Maastricht, Netherlands. Dr. Visser states that she has no financial interest in the products or companies mentioned. She may be reached at e-mail: nienke.visser@ mumc.nl.
- Visser N, Berendschot TT, Bauer NJC, et al. Accuracy of toric intraocular lens implantation in cataract and refractive surgery. J Cataract Refract Surg. 2011;37:1394-1402.