Ophthalmologists occasionally find themselves in need of accurate records concerning the size of structures on the living retina. This need is perhaps of greatest importance if a lesion is encountered with some of the characteristics of a neoplasm, when a slight increase in size may verify the diagnosis. It is also, however, of interest to procure an exact record of the diameter of the nerve head if questionable papilledema or blurring of the margins is present. The size of hemorrhages and exudates and the width of blood vessels are also sometimes of importance. Such measurements are also useful for localization of lesions and for descriptive purposes.
Measurements on the retina can be made by means of the Gullstrand ophthalmoscope fitted with a micrometer ocular, or by photographing, or having an accurate drawing made of, the fundus. These methods unfortunately are not available to all practitioners, nor are they