The operation in the latter instance, although not yielding very satisfactory results with regard to the reattachment of the retina, may be carried out with some hope of success in certain cases. Before performing the operation the pathological cause of the detachment should be carefully investigated, for it is obvious that it would be useless to perform the operation in a case of detachment due to a choroidal tumour or if definite bands of fibrous tissue could be seen in the vitreous pulling off the retina. Undoubtedly it should be undertaken as soon as possible after the detachment has occurred and the puncture should enter the space filled with subretinal fluid. Whether the puncture should penetrate the overlying retina is still a disputed point. After the operation a pressure bandage should be applied and the patient should be kept on his back and not allowed to raise his head from the pillow for at least three weeks. This latter part of the treatment is most essential; indeed as good results may be obtained with complete rest as by performing scleral puncture. Unfortunately, recurrence is very liable to take place whichever method be used, even if reattachment of the retina be obtained. =Instruments.= Speculum, fixation forceps, Graefe’s knife. =Operation.= Under cocaine. If no special position be indicated the puncture is best made upwards and inwards. The patient is made to look outwards and downwards. The conjunctiva over the sclerotic, well behind the ciliary body, is drawn down so that when released it shall form a valvular opening to the scleral wound. The Graefe’s knife is driven through the conjunctiva and sclerotic, the incision being made antero-posteriorly in the direction of the fibres of the sclerotic to avoid wounding the choroidal vessels. It is probably better to enlarge the wound when withdrawing the knife than to turn the latter at right angles before it is withdrawn, as has been recommended by some surgeons. A bead of vitreous usually escapes under the conjunctiva. If the tension be not lowered, gentle massage of the globe through the lid should be employed. PARACENTESIS OF THE ANTERIOR CHAMBER =Indications.= Evacuation of the contents of the anterior chamber is performed for several conditions:-- (i) To reduce the tension of the eye when due to an altered consistency of the aqueous, as for instance in cyclitis. (ii) To evacuate pus from the anterior chamber following metastatic infection. (iii) To evacuate the anterior chamber in bad corneal ulceration, especially when associated with hypopyon and tension. (iv) To examine the aqueous for organisms in cases of cyclitis following operation or of metastatic origin. (v) To evacuate soft lens matter (see p. 194).