In emmetropia, if the lens be removed, a glass of + 11 D. has to be placed before the eye for distance vision and + 14 D. for near vision. It is impossible to predict the exact amount of correction of myopia which will be produced by the removal of the lens, owing to the surgeon’s inability to estimate the refractive power of the lens associated with the distortion of the posterior pole of the globe. Usually a patient with about 22 D. of myopia is rendered emmetropic by the operation. There are two main objections which have been raised to the operation: first, that there is a slight risk of septic infection, sympathetic ophthalmia even having been known to occur; secondly, that retinal detachment seems rather more common after operation than in ordinary myopia of the same degree. As a rule it is only advisable to perform the operation on one eye, the patient using the other for reading purposes, but under certain circumstances, as when the operation has been successful for a considerable period of time, it would be justifiable to perform it on the other eye. The operation should never be performed on patients having only one eye. =Instruments.= Speculum (Fig. 85), fixation forceps (Fig. 86), discission needle. =Operation.= _First step._ The operation is best performed by artificial light. The pupil having been dilated with atropine and the eye anæsthetized with cocaine (a general anæsthetic being necessary, however, for young children), the speculum is inserted by first drawing up the upper lid, making the patient look down, and inserting the top blade, and then drawing down the lower lid, making the patient look up, and inserting the lower blade. The speculum is opened to its full width without undue strain on the canthus and is kept in position by tightening the screw. The eye is steadied by fixation forceps held in the left hand, which grasp the conjunctiva as close to the cornea as possible directly opposite to the spot at which the puncture is to be made; the puncture is made directly behind the limbus and the needle is passed into the anterior chamber. _Second step._ Using the shaft of the needle lying in the cornea as a fulcrum on which to rotate the needle, an incision is made in the anterior capsule of the lens, and the lens fibres are broken up by a stirring movement. The needle is then rapidly withdrawn in the same plane in which it was inserted so as to avoid making a crucial incision in the cornea with the spear-like end and thereby losing the aqueous. The best way to make sure of this is to mark one side of the handle so that it may be inserted and withdrawn in the same position. A pad and bandage are then applied. =After-treatment.= The pupil should be kept dilated subsequently by the use of atropine twice a day until the lens has become absorbed. The bandage may be removed about the fourth day and dark glasses worn.