More Than Meets The Eye: How To Optimize 3-D Visualization To Improve Vitreoretinal Surgery

A more recent platform that can be utilized for visualization during vitreoretinal surgery is the 3D heads-up display (HUD). In a standard operative microscope (SOM) the surgeon operates looking through the binoculars of the microscope. In the 3D HUD Visualization System, a stereo pair of high dynamic range cameras with controllable apertures is attached to the surgical microscope and transmits overlapping images to a high-definition 3D screen. The surgeons wear polarized glasses to provide a stereoscopic view of the monitor.1,2

When compared the SOM with 3D HUD, several studies highlight the advantages of the 3D HUD, which include enhanced stereopsis, wider depth of field, improved ergonomics, increase magnification with a larger field of view, and decreased endoillumination requirements. Talcott et al in a prospective study randomized 1:1 to undergo surgery with a 3D HUD surgical platform or SOM.  The study found that the minimum required endoillumination was significantly lower with 3D HUD (mean 22.70%±15.10% SD) compared with SOM (mean 39.06%±2.72%; P<0.001) during macular surgery.The possibility to decrease illumination during the vitrectomy is a great advantage because the macula can be exposed to a high-intensity light beam at close proximity and is therefore susceptible to thermal and photochemical damage. 

Further advantages pertain to the applicability of instant digital filters (e.g., to enhance vitreous visibility or identification of ILM tissue). According to previous studies, color gains can be adjusted to augment contrast for particular situations. Alteration to make the image appear somewhat red enhances visualization of indocyanine green stain, adjusting color gains to make the image look yellow-orange enhances the faint staining of brilliant blue G stain. Reducing the red gain reduces the red reflex, making the image look blue and enhancing visualization of vitreous.

The purpose of our study recently published in OSLI-Retina was to define parameters to determine which optical parameters profiles (OPP) can be utilized to improve the visualization of epiretinal membranes (ERM) and the internal limiting membrane (ILM) using a three-dimensional heads-up microscope during 25-gauge pars plana vitrectomy (PPV).

Brightness, contrast, gamma, hue, and saturation were adjusted in each of the 11 OPPs created. Brightness refers to the absolute value of colors (tones) lightness/darkness. Contrast describes the differential between light and dark areas of an image. Gamma is used to adjusts the mid tones from the tonal scale optimizing the contrast and brightness in the mid tones. Hue refers to the attribute of visible light as it is differentiated from or similar to the primary colors: red, green, and blue. Saturation defines the brilliance and intensity of a color. The grader’s responses indicated that higher values of hue and contrast are correlated with better visualization of ERM before dye application and better visualization of ILM after ICG dye application. 

Intraoperative photographs of each unique optical parameter profile during heads-up surgery. Figure A: Before the use of Indocyanine dye; Figure B: after use of Indocyanine dye

Facilitating the use of these color channels, the most recent software upgrade (version 1.4) has improved the ability to change color parameters on the fly. In this software version, users are presented with previews of the color channels in a live image to tell which channel is best in real-time.  Also, there is an expansion of present channels and image temperature controls for users to further refine their surgical parameters. 

Version 1.4 Software Allows For Heads Up Modification Of Color Profiles

The use of optical parameter profiles to improve visualization of specific structures is still new and is heavily dependent on surgeon preference. The potential advantages of the digital platform in the context of retinal surgery are vast. While the investigation into the platform’s full potentials still in the early stages, studies such as this will be instrumental in driving forward the use of this technology.

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