The present invention is an improved method of providing flexible image possessing in a visual prosthesis by providing downloadable video filters. In a visual prosthesis, the input video image is normally higher resolution than the output stimulation of the retina, optic nerve or visual cortex. It is advantageous to apply video processing algorithms (filters) to help provide the most useful information to the lower resolution electrode array. Different filters are more effective in different environments and for different subjects. Examples of situation dependent filters include reverse image, contrast increasing, edge detection, segmentation using chromatic information and motion detection. Filters loaded in the video processing unit may be selected dynamically to suit the situation or the user's preference. It is therefore advantageous to provide flexibility in applying filters. However, it is also important to maintain the security necessary for a medical device.