_Acute glaucoma_ is by no means an infrequent complication--indeed the author has seen four successive cases of conical cornea, operated on both by excision and by the cautery, followed by this complication. It is probably due to adhesion of the root of the iris to the back of the cornea during the time the anterior chamber is empty. It can usually be relieved by an iridectomy. =The electro-cautery operation.= The operation generally adopted is known as the target operation. It consists in surrounding the apex of the cone with two rings of cautery marks, the outer made at a dull red heat, the inner with the point slightly brighter, whilst the apex is cauterized at a red heat, so that rings of different depth are obtained. Cauterization of the apex should stop just short of perforation, the inner ring being deeper than the outer. With this method secondary glaucoma and anterior synechiæ are not so liable to occur. On the other hand, an optical iridectomy has to be performed more frequently. A few surgeons still cauterize the apex of the cone until a perforation is produced. This latter operation seems to have the disadvantages of both methods and the advantages of neither. REMOVAL OF TUMOURS INVOLVING THE CORNEA Tumours which involve the cornea are usually secondary to tumours occurring at the limbus. The chief of these are: _simple_--dermoid patches, moles of the limbus; _malignant_--sarcoma, endothelioma, epithelioma. Dermoid patches should be shaved off as close to the cornea as possible; the white area left after their removal can be improved by tattooing. Malignant tumours in very early stages may be removed locally with scissors and forceps, the cautery being applied to their base, since they do not tend to invade the sclerotic deeply. TATTOOING THE CORNEA =Indications.= (i) To do away with the blinding effects of light through a scar after iridectomy has been performed (see p. 215). (ii) To simulate a pupil on a white scarred cornea. [Illustration: FIG. 128. TATTOOING NEEDLES.] The operation is not without risks, as it may light up old inflammation in a previously quiet eye. Panophthalmitis and sympathetic ophthalmia have both been known to follow it. The pricking of the needle may carry in epithelium and implantation dermoids may arise. =Instruments.= A fine single needle is generally used, occasionally a bundle of needles (Fig. 128). =Operation.= Under cocaine. Chinese ink, sterilized and prepared by rubbing up with 1-6,000 perchloride of mercury, is smeared over the area to be tattooed. Multiple punctures in an oblique direction are then made into the cornea over the area desired. More paste is then rubbed in over this area. The cornea should be intensely black after the operation, as a certain amount of the ink is carried away by phagocytosis and shedding of the epithelium. Subsequent reaction may be reduced by means of an iced compress. Atropine should be instilled. SCRAPING CALCAREOUS FILMS