Interference filter for colour and black-and-white fluorescein angiography.

A new dichromic interference filter was used as the excitation filter in colour and black-and-white fluorescein angiography of the human fundus. The interference filter transmits light shorter than 490 nm (blue) and longer than 640 nm (red). In colour photography the red light shows the topography of the fundus. In black-and-white photography, the red light is prevented from reaching the fundus by an additional absorption filter used together with the interference filter. These two comprise the excitation filter, which eliminates the pseudo-fluorescence from black-and-white angiograms.