Every ophthalmologist has experienced the difficulty encountered in the determiation of a minute central scotoma. This has repeatedly been stated by authors known for their work in perimetry and has been personally confirmed by my colleagues. A patient may say that he has difficulty in reading or that he tires easily on doing close work, or he may state positively that he has an impairment of his sight. Examination shows his visual acuity to be normal, and although one cannot make out a defect of the central field with the usual methods, his trouble definitely suggests the presence of a central scotoma. As Traquair1 wrote : "Difficulty may arise in connection with the patient. A few patients although they have sufficient central vision cannot be induced to fix correctly, but persist in following a test-object with the eye." The value of Haitz's stereoscopic charts, Lloyd's stereocampimeter and Walker's macular selector