The operation is usually performed through an incision directly behind the limbus. In the case of corneal ulceration it is sometimes performed by dividing the base of the ulcer with a Graefe’s knife (Sämisch’s section). When collecting the aqueous for bacteriological examination, a sterile hollow needle with a point similar to a discission needle, attached to a hypodermic syringe, should be passed into the anterior chamber at the limbus and the fluid withdrawn into the syringe by an assistant (Fig. 123). The spot through which the needle is passed is first touched with the electro-cautery to ensure asepsis. =Instruments.= Speculum, fixation forceps, bent broad needle, iris spatula. =Operation.= Under cocaine. The puncture is usually made upwards and outwards unless there be some other special indication for its position, such as a mass of pus in the lower angle of the anterior chamber. The eye is fixed opposite the spot at which the puncture is to be made, and the bent broad needle is passed into the anterior chamber through an incision directly behind the limbus. The needle is then withdrawn and is usually followed by a rush of aqueous. The remainder of the aqueous is then evacuated by pressing the lower margin of the wound with an iris spatula. In some cases where a very tenacious hypopyon is present it may be withdrawn with the iris forceps. The only complication liable to occur is prolapse of the iris into the wound, which should be replaced with the spatula, or failing that, removed. [Illustration: FIG. 123. HOLLOW NEEDLE USED FOR PARACENTESIS OF THE ANTERIOR CHAMBER. This is used when it is desired to examine the aqueous bacteriologically. Care should be taken to see that the cutting blade is sufficiently wide to take the shaft of the needle.] OPERATIONS FOR PENETRATING WOUNDS OF THE GLOBE =Indications.= Of all the conditions which a surgeon is called upon to see, penetrating wounds of the globe may present the most difficult problems as to treatment. The most important factors in their treatment and prognosis are-- 1. _The time at which the patient presents himself for treatment_ and the condition of the wound are all-important in the prognosis. Thus in the case of a wound which is obviously septic and going to terminate in panophthalmitis the eye should be eviscerated. 2. _The position and extent of the wound._ Formerly it was taught that if the ciliary body were wounded the eye should be excised. The reason for this was that these injuries were so frequently followed by sympathetic ophthalmia owing to prolapse of the iris and ciliary body. It is now generally recognized that sympathetic ophthalmia only follows if the wound becomes septic, irido-cyclitis with keratitis punctata being present, and it is only after the latter symptom manifests itself that the eye should be excised, provided that the wound be not so extensive as to preclude all chance of recovery from the outset.