Either a chemical or the actual cautery may be used.
Indications. Corneal ulceration. The cornea being extremely dense, organisms do not penetrate very deeply into its substance, so that destruction of the bacteria is effected by cauterization of the spreading portion of an ulcer; the albumin is also coagulated and so a barrier is presented to their advance.
Operation. The eye is thoroughly cocainized, and the spreading portion of the ulcer is first defined by staining with fluorescine, washing away the excess of stain with boric lotion.
By a chemical caustic. Liquefied carbolic (carbolic acid crystals liquefied in 10 per cent. of water) is applied upon a sharpened match. Any excess should be removed so as to prevent its running on to the cornea. A speculum is inserted and the cornea is dried by blotting with cigarette paper; the stained area is lightly touched with the point of the stick, particular attention being paid to the spreading margin. A dense white plaque is the result; this usually clears up in a few days. Atropine ointment is applied daily to the conjunctival sac.
Fig. 127. Electro-cautery.
By the actual cautery. The electro-cautery (Fig. 127) point should be extremely fine and only raised to a dull red heat. The stained area should be touched lightly with the point.
The actual cautery is best for serpiginous corneal ulcers, carbolic acid being more satisfactory for those of the vesicular type.
OPERATIONS FOR CONICAL CORNEA
Indications. Since the operation for conical cornea is not without serious risks, it should only be undertaken when the vision cannot be improved with glasses to 6/18; high + or - cylinders will often yield satisfactory results. The object of all forms of operation is the flattening of the cone.