One reason why I did not rest satisfied with the effects produced by the hydrocyanic acid, was, that its action, like that of all other medicines, decreased in power by continued application; thereby rendering it necessary to have occasional recourse to other medicines, in order to insure a more speedy recovery. Another reason was, the reluctance of many individuals to submit the eye to the action of so potent a medicine.
The first medicines to which I shall refer, and which I have employed with some success, are the _chlorocyanic acid_ and _sulphuretted chyazic acid_. The plan I pursue is that of putting a drachm of one of the medicines into a bottle (containing a small piece of sponge) of about two-ounce size, having a mouth precisely fitted to the eye, and with a ground-glass stopper.
The action of these medicines is very different from that of the _hydrocyanic acid_, in as far as they both stimulate the eye, and produce much greater warmth and irritation, with less dilatation of the pupil. Few, however, can bear the _chlorocyanic acid_ to be applied longer to the eye than half a minute; though, in a minute after its application, all irritation is removed, and the eye feels perfectly at ease.
The next medicine which I have employed in the form of vapour was the chloruret of iodine. This medicine produces very little warmth or uneasiness to the eye, if continued for the space of two minutes or upwards; but a sensation of irritation, accompanied with a flow of tears, takes place on its removal. It contracts the pupil, and in no case have I seen it dilate it. Its vapour rises very readily, and does not leave the yellow disagreeable colouring on the skin produced by the vapour of iodine when uncombined, which is a great drawback in the use of iodine in diseases of the eye.
The last medicine which I have employed is the bisulphuret of carbon, which is so volatile, that the application of it to the eye, when the bottle is held in a warm hand for a few seconds, is as much as can be borne, in consequence of the intense prickling heat and flow of tears which it occasions. Owing to this fact, I generally use it by causing the patient to shut the eyelid during its application, which can then be continued for a minute or two, with the same beneficial effect upon the eye, without inconvenience to the patient. It generally contracts the pupil, and very seldom dilates it.