Positional control of laser photocoagulator lesions near the fovea.

THE design and use of laser photocoagulators for the treatment of pathological conditions in the eye has been described by Ingram, Manson, and Smart (1965) and Ingram (1966). When lesions need to be made close to the fovea, extremely precise positional control of the lesion is necessary. Involuntary eye movements (Boyce, 1967; Ditchburn and FoleyFisher, 1967) and human reaction times become important sources of error. With conventional photocoagulators destruction of part of the fovea could obviously ensue. This paper describes an optical system which nullifies such sources of error; once the site for the lesion is chosen, the actual lesion must occur there and nowhere else, despite eye movements and length or number of the exposures.