The principle of Mr. Bowman's most excellent operation is, that the punctum, canaliculus, and nasal duct resemble in many respects the urethral passage, and in cases of stricture require to be treated on the same principle. If, then, it were possible to pass instruments gradually increasing in size through the seat of stricture, it would be gradually dilated. It is, however, in the normal state of parts, impossible to pass any instrument beyond the size of a human hair past the curve which the canaliculus makes on its entrance to the duct, hence the proper dilatation cannot be performed. Again, it is found that the puncta, specially the lower one, are themselves very often to blame, in cases of watery eye, sometimes because they are inverted or everted, more often because, sympathising with the lid, they are turgid, angry, and inflamed, pouting and closed like the orifice of the urethra in a gonorrhœa.
Mr. Bowman found that by slitting up the inferior punctum and canaliculus as far as the caruncula, several advantages were gained:—(1.) The swollen, angry, displaced punctum no longer impeded the entrance of the tears; (2.) and chiefly when the canaliculus was slit up, the curve, or rather angle, which impeded the passage of probes, was done away with, and the nasal duct could be readily and thoroughly dilated.
Operation.—The surgeon stands behind the patient, who is seated, and leans his head on the surgeon's chest. The affected lid is then drawn gently downwards on the cheek, so as to evert and thoroughly expose the lower punctum. Into this the surgeon introduces a fine probe of steel gilt, the first inch of which is very thin, especially at the point, and deeply grooved on one side, exactly like a small (and straight) Syme's stricture director.
Keeping the canal relaxed by relaxing his hold on the lid, the surgeon now gently wriggles the probe along the canaliculus, gradually stretching it as the probe advances, so as to avoid catching of the sides of the canal before the point of the instrument, till he is satisfied that it has fairly entered the nasal duct. He then stretches the eyelid, brings the handle of the probe out over the cheek so as to evert the punctum as much as possible, and then with a fine sharp-pointed knife enters the groove (Fig. ix.), and fairly slits up the punctum and the canal to the full extent. The incision should be as straight as possible, and through the upper wall of the canaliculus. A dexterous turn of the instrument upwards on the forehead will generally enable it to be passed at once fairly into the nose through the nasal duct, the usual rule being observed of passing it downwards and slightly backwards, the handle of the probe passing just over the supraorbital notch.
Fig. ix. [84]
For several days after the operation the probe will have to be passed, both to prevent the wound in the canaliculus from healing up, which it is too apt to do, and also to gradually dilate the nasal duct if it has been previously strictured. Probes and directors of various sizes are required; in fact very much the same instruments (in miniature) as are required for the treatment of stricture of the urethra.
Mr. Greenslade has invented a very ingenious little instrument, of which, through his kindness, I am able to show a woodcut (Fig. x.), for slitting up the canaliculus without having to fit the knife in the groove.
Fig. x.