Red-Free Light Fundus Photography

Photographic Optogram

¹ Department of Ophthalmology, Nagoya City University Medical School Mizuho-Ku, Nagoya, Japan

Red-free light fundus photography has been developed to compare rhodopsin contents in the retina during light and dark adaptations by means of a filter with a wavelength of 500 nm. In order to avoid a probable artifact by the photographic procedure, half of the fundus, either upper or lower half, is irradiated after dark adaptation, and a red-free light fundus photograph is taken. This half occlusion procedure is assumed to be similar to an optogram and is able to differentiate the degree of rhodopsin contents in situ in the same picture. The new technique has also opened new vistas in determining retinal regions lacking the ability of rhodopsin synthesis in patients with night blindness. This principle is also applicable to detect minimum changes in the vascular system and nerve fibers in the retina.