Heads Up!

In heads-up surgery, the surgeon performs microsurgical procedures, not by bending over and looking through the eyepieces of a surgical microscope, but by viewing images sent from a three-dimensional (3-D) camera on a large flat panel display. My department has adopted this technology, and our five “heads-up” surgeons have now performed over 3,500 cases. However, there are only a few studies available on this technique, and most of these concentrate on the anterior segment. So when I discuss the use of heads-up surgery, I receive some common questions.

The first: is “Isn’t it difficult?” The short answer is no, not at all. We have young and old surgeons doing it, and anyone can learn within a couple of days. Another is “How good is the 3D image compared to a direct microscope view?” Well, we performed a study (1) in which we measured the depth of field, and found little difference between the heads-up view and the view through the microscope. We also measured the resolution and found it to be around 30 percent lower than traditional microscopy. This isn’t surprising, since the retina has incredible resolution. For example, for a visual field of 120 degrees, theoretically more than 500 megapixels have to be filled in order to make the display image indistinguishable from the surgical microscope image for our eyes. But this is only valid with eye movement. If the eyes are not moved to scan the whole image with the fovea, the brain only receives an image with a resolution of seven megapixels, in the area of foveal fixation, and one megapixel elsewhere. My camera system delivers a resolution of four megapixels, and in the future the pixel density will increase, until the pixels are no longer detectable.

Another important feature is dynamic range. My two-year-old camera which I used before I switched to heads-up surgery,  had a small dynamic range. In contrast, my TrueVision camera today has a dynamic range of 14 f-stops. What huge progress in only two years! We can expect further improvement if – instead of a camera placed on top of a traditional microscope, where it receives only a virtual image – we use a fully digital microscope, where the camera sensor receives the true image directly.

The large image is another major advantage of heads-up surgery. In our department, we feel that the large image improves depth perception, allowing for more precise surgery. Illumination has always been an issue for the vitreoretinal surgeon, but digital image processing that brightens the image can also help us during surgery. Then there’s ergonomics – which would you prefer, a hunched posture, or one that allows you to move your neck, head, and back? And when it comes to teaching, for the first time surgeons in training can see exactly the same image as the surgeon is seeing. The large projected image makes this effective and comfortable for both of them.

Looking forward, overlay guidance systems may also be of some use for vitreoretinal surgery, and another useful tool which could be integrated is intraoperative OCT – you could simply split the screen and view both. In my view, the benefits of heads-up surgery are undeniable – and provide a strong argument for a future in which we stop looking through eyepieces to perform surgery.