A clinical study was conducted in 110 cases of subjective aniseikonia, a syndrome that is often neglected. After in practice summarizing the different distortions composing the phenomenon of aniseikonia, a description of the prototype apparatus used for the experiments is given: it is eikonometric stereo-projector the originality of which lies in the measuring system, constituted by the projected stereograms. Three parameters were studied: depth-perception, peerception threshold of anseiikonic disparity, and value of the found aniseikonia. The results are presented in relation to 3 groups of subjects: 14 emmetropic, 32 isometropic, and 64 anisometropic, 32 isometropic, and 64 anisometropic patients, including 24 monocular aphakic. The author shows the advantage of contact lens correction in the last cases: with an average of 3.5 p. cent, the found aniseikonia was always inferior to 6 p. cent and to the theorectical levels currently accepted. Finally, the phenomenon of "cortical malleability" arises in the adaptation of the patient to his optical correction and could regularly and progressively be increased.