Perception of light and recognition of its projection in an eye with cataract may be investigated by means of a beam of light 2 or 3 mm. in diameter directed from a distance of 36 cm. The apparatus employed is the ordinary ophthalmologic lamp, but this has a circular opening 2 or 3 mm. in diameter which throws out a fine beam of light (fig. 1). With the lamp placed beside the head of the patient, this beam is received by a concave mirror 36 cm. from the eye with the cataract (fig. 2) ; the mirror reflects the beam toward that eye. The beam must be directed from in front, from above and below and from inside and outside in order that the perception of light by the posterior, lower, upper, external and internal segments of the retina may be investigated. The examination may also be performed with the mirror