_Local_ anæsthesia is obtained by the use of a 4% solution of cocaine instilled four or five times before the operation at intervals of three minutes; a drop of the solution should also be instilled into the eye which is not being operated on, to prevent an accidental reflex stimulation of the conjunctiva and screwing up of the eyes. Adrenalin (1-1,000) may be used in conjunction with the cocaine; it is especially useful in squint operations, as it lessens the hæmorrhage. Eucaine and stovaine have been used, but are not nearly so satisfactory. Under ordinary circumstances the only pain felt during an intra-ocular operation is during removal of the iris; this is obviated to a great extent by instilling the cocaine at least 15 minutes before the operation is performed, so as to allow time for its diffusion into the anterior chamber. The patient should be warned when to expect the pain, so that he may not move; his self-control may be tested beforehand by pricking the nose with a pin. _The theatre._ The theatre should possess, as far as possible, all the modern improvements found in an up-to-date general surgical operating-room. The light should proceed from a single large window, which, if possible, should face the north. _The window_ should consist of a single pane of glass or of two panes forming the angle of the theatre; it should begin about 5 feet from the floor and should extend to the ceiling (Fig. 74). The advantage of an angular window is that it allows the operator to stand with his back to the light in the angle, and so enables onlookers to see. No top light should be allowed, as it produces a corneal reflection which may prevent the operator from seeing the position of his knife in the anterior chamber. Beneath the window there should be a recess for the end of the operating table, so that the patient’s face can be brought close to the window if necessary (Fig. 74). This recess is formed by building the main wall of the theatre further out than the window, which has to be supported by a transverse girder. [Illustration: FIG. 75. BULL’S-EYE ELECTRIC HAND-LAMP. For use when artificial illumination is required.] The window should be fitted with outside blinds so that the theatre can be easily darkened for the operations, such as capsulotomy, which require the use of artificial light. The best artificial light is a small enclosed electric hand-lamp fitted with a bull’s-eye, by means of which the operation field can be brilliantly illuminated while the surrounding area is left in comparative darkness (Fig. 75). Failing this, a single powerful lamp with a ground-glass globe, placed in front of the patient, will serve, the rays of light being brought to a focus on the eye by means of a large convex lens of about + 10 D.