Electronic subtraction method for ophthalmic photography.

A commercial electronic subtraction unit originally intended for the study of roentgenograms was used to produce subtraction pictures of fundus fluorescein angiographies. No modifications were needed to make good quality subtraction pictures. The method is fast and inexpensive in contrast to previously described photographic methods. Certain limitations of the present equipment are discussed as well as some possibilities for further development of the apparatus. The method is especially suitable for studies on dynamic processes in the eye and it should prove valuable in the long-term follow-up of chronic diseases such as glaucoma and diabetic retinopathy.