This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
Electricity should never be employed in this affection. if there be any reason to suppose that it depends on active congestion, inflammation, or other organic disease in the nervous centre of vision, the nerve itself, or its expansion on the retina. In purely functional cases, it may sometimes be used with benefit; but galvanism is here more effective than the induced electricity. In doubtful cases, it may be applied over the face and about the orbit in the first place, in order to excite the eye through the ramifications of the fifth pair, which have a peculiar influence over vision when galvanically excited; and, if this measure is unsuccessful, the application may be made to the ball of the eye, in order directly to excite the optic nerve; one pole being placed in the orbit, and the other at the back of the neck. Acupuncture of the parts about the eye has been brought to the aid of galvanism; and many cures of incomplete, and some of complete amaurosis have been reported, supposed to have been obtained in this way. (See Channing, Medical Application of Electricity. Boston, 1852, p. 87.) The electro-magnetic instrument with two wires may also be used for this purpose, though less effective than the battery.