Enhanced diagnostics

Dr Becker performing surgery with the aid of imaging technology. With heads-up surgery, surgeons do not use the eyepieces of the microscope anymore. Through 3D glasses the surgeon and staff can watch the microscope view with a 3D monitor. Courtesy of Matthias Becker MD New three-dimensional (3D) digital imaging technologies are providing enhanced diagnostics of macular disease and greater ease in the visualisation and performance of vitreoretinal surgery. Among the new 3D imaging tools becoming available are enhanced 3D optical coherence tomography (OCT) systems that allow the detailed exploration of the macular region at a microscopic level, and heads-up surgery visualisation systems that allow not only the surgeon but the whole surgical team to observe ophthalmic surgery in high-definition 3D. Susanne Binder MD noted that OCT imaging of the retina has revolutionised the field of retinal disease treatment. It provides the ability to perform in vivo histology on retinal tissues before and after treatment. In addition, when used intraoperatively, OCT enables better membrane peeling, reduces the need for dyes, and allows better visualisation of vitreomacular traction and subretinal fluid behaviour. It can also be used in hazy media. “The fusion of the microscope and the OCT image adds a new dimension to vitreoretinal surgery – we can see more, we can perform better and it actually does simplify our work flow,” said Dr Binder, Rudolf Foundation Clinic, Vienna, Austria. The addition of 3D imaging to intraoperative OCT is the logical next step and this has been employed with some success by Cynthia Toth MD at Duke University, Durham, North Carolina, USA, Dr Binder noted. However, she suggested that 3D intraoperative OCT may not realise its full potential until the noise in the images can be filtered out in real-time. Currently, the post-processing of raw OCT data into a noise-free virtual 3D rendering takes about 30 minutes. FANTASTIC VOYAGE In the meantime, the post-processed images allow the clinician to take virtual flights through the macular tissue at a microscopic level. The improved visualisation reveals many features not visible with two-dimensional (2D) OCT and can help guide treatment decisions and provide further insight into the recovery processes of retinal tissue, Dr Binder said. In one video clip, Dr Binder showed a case where an eye with vitreomacular traction appeared to be a good case for enzymatic vitreolysis when viewed by conventional 2D OCT. However, 3D post-processed rendering showed the presence of many vitreomacular adhesions, which is a strong contraindication for the treatment. She also presented cases of retinal detachment where one could differentiate much more clearly whether or not the macula was attached than was possible with conventional clinical examinations. “For the future, I strongly believe we will have full 3D intraoperative OCT and that will provide an overview of the eye. Later on we can move to a cellular level and use adaptive optics,” Dr Binder said. HEADS-UP 3D Another new 3D approach is the new heads-up NGENUITY® (Alcon) 3D surgical viewing systems, where instead of the surgeon looking directly through the surgical microscope, the surgeon and the nurse wear 3D glasses and view the surgery on a 3D monitor. The system consists of a high-dynamic-range surgical camera with a three-megapixel resolution and a high-definition monitor. This new approach offers the potential advantage of facilitating surgery using lower light levels than when using a surgical microscope. It also has a high dynamic range that provides increased colour contrast and comparable depth-of-field, said Matthias Becker MD, PhD, Triemli Hospital, Department of Ophthalmology, Zurich, Switzerland. Dr Becker described the experience he and his associates had with the new heads-up 3D visualisation system over a three-week testing period. During that time, they used the system in 21 consecutive patients and 25 patients undergoing posterior segment surgery. Their retinal conditions included 10 cases with retinal detachment, six with epiretinal membrane, one with macular hole and four undergoing silicone oil removal. He noted that the system was fairly simple to use, although it requires an additional staff member to manage the camera-monitor interface controls. In two cases the surgeon had to return to the surgical microscope for safety reasons. He added that it definitely improves training. Moreover, the improved visualisation of the vitreous it provides could reduce the need for triamcinolone and dyes for that purpose. However, although the light sensitivity of the camera reduces light toxicity to the retina, it also means that the camera is more sensitive to media opacities. There is also a delay of about a tenth of a second between real-time and the image on the monitor, which means that instruments can appear to be 'floppy' when performing surgical manoeuvres quickly. “My personal summary is that there is nothing like a trained human eye-brain visual system which can compensate and extrapolate from foggy reality to clear visualisation, so don't get lured into a false sense of security,” said Dr Becker. Susanne Binder: 
susanne.binder@extern.wienkav.at Matthias Becker: 
matthias.becker@zuerich.ch