The Laboratory of Bioengineering and Physical Science supports the NEI through innovative and independent optical design approaches to address the unique requirements of clinical and basic research studies. Modification of a fundus camera to capture an electro-retinogram following laser stimulation of selected areas of the retina and to photograph the selected area. There are five main components to this optical system. First, a helium neon laser (633 nm) was made collinear and coincident with an argon ion laser (488 nm) or triggered xenon flashlamp and serves as a surrogate light beam during patient alignment for the electro-retinogram stimulating pulsed argon laser or xenon flashlamp. Second, within the parallel light space of the optical path, a variable aperture can be freely positioned laterally to the light path such that it allows the physician to adjust the size and position of the area of illumination on the retina. Third, a final focusing lens of appropriate focal length and f-number is chosen to cover a maximum area (i.e. at full aperture), after reaching a focus at the lens of the eye, equivalent to the optic nerve. Fourth, a glass beamsplitter introduces the modified optical path of the surrogate and stimulating lasers into the optical path of the fundus camera, such that both pathways are coincident. Fifth, a vertical polarizer is introduced into the laser path prior to the beamsplitter and a second horizontal polarizer is introduced into the observation pathway of the fundus camera. The significance of this is that it allows depolarized light from the retina to be observed, but eliminates unwanted specular reflections from optical surfaces, most particularly the cornea. Rotation of either polarizer renders this reflection visible, if required. A preliminary clinical evaluation is on-going to capture ERG responses in normal and diseased areas of the retina. This work was awarded a patent, publication date March 13, 2012 entitled: "A Fundus photostimulation system and method" Francisco De Monasterio, Paul D. Smith, Edward Wellner.