For the past three years I have used an absolute monochromatic ophthalmoscope of my own design and have compared observations with those made with the ordinary electric type. A spectroscope insures the monochromatic quality of the colors used in my ophthalmoscope.
Several hundred careful fundal examinations were made on normal persons as well as on those with pathologic conditions. These studies were temporarily discontinued1 at about the time that a comparison of the fundal pictures as observed with my monochromatic ophthalmoscope with those obtained with the so-called "red-free" ophthalmoscopes now in general use was to be made. In this way it was hoped to determine what merit, if any, an absolute red-free ophthalmoscope has over the others in which colored filters are used without particular attention to their red-free quality.
The instrument consists of a lamp house (A) in which is incorporated a mercury vapor lamp with an exhaust