Augmented reality fundus biomicroscopy - A working clinical prototype

Background: To guide treatment for macular diseases and to facilitate real- time image correlation, measurement, and comparison, we developed a method for direct overlay of previously stored photographic and angiographic image s onto the real-time slitlamp fundus view. Methods: Previously acquired fundus photographs and angiography images were digitized. A slitlamp interfaced to a charge-coupled device camera, frameg rabber, and computer allowed for real-time acquisition and digitization of slitlamp fundus images that was synchronous with posterior segment examinat ion. Custom-developed video injectors containing a miniature cathode ray tu be display allowed for real-time superposition of angiographic images to th e fundus view. Registration and tracking algorithms were developed and depl oyed in C++. The feasibility of this approach was demonstrated in 5 human s ubjects. Results: The computer-vision algorithms provided robust registration, track ing, and image overlay of previously stored photographic and angiographic i mages directly onto the real-time fundus view. Accurate tracking was demons trated with updates at 3 to 5 Hz. Direct overlay of previously stored image s confirmed registration accuracy, but examiners preferred a more simple re ndering that included only relevant information and eliminated extraneous, potentially confusing image data. Conclusions: Slitlamp-based video injection of previously stored images all ows for accurate, robust, realtime correlation and comparison to the biomic roscopic fundus view in human subjects.