In no branch of muscle work is there as much uncertainty and confusion, both as to diagnosis and as to treatment, as in the subject of hyperphoria. Diagnoses vary as widely as the test by which the diagnoses are made, and the treatment varies still more widely. These tests and treatments have all been successful part of the time ; else they would not be persisted in, but the chief difficulty seems to be in the proper use of the tests, the correct interpretation of the findings, the correct diagnosis and the best choice of treatment for the particular case at hand. The common mistake is to have a more or less pet plan of procedure and to make each case conform to this plan. A very common statement in textbooks is to correct two thirds of the hyperphoria by prisms ; for example, if the phorometer shows 6° of