London, England. Mr. President and Members of The Chicago Ophthalmological Society: As the hour is late I propose to take up only the principal points in connection with my subject and to deal with each one shortly. First: The operation of trephining is suitable, not merely for chronic cases, but for sub-acute and acute cases of glaucoma as well. I would urge on your attention that, of all the operations dealing with glaucoma, this one involves the minimum of surgical violence, and should, therefore, in acute cases be the operation of choice. It is, moreover, much safer than any other operation I know of, and is no less certain in its results. I do not advise trephining in the secondary glaucoma following intumescent cataract, for in such cases the semi-fluid lens bulges into and blocks the trephine hole. Nor for obvious reasons do I recommend it in cases where there is reason to believe that a communication exists between the aqueous and vitreous chambers. Second: The object of trephining is to tap and permanently drain the aqueous fluid from the anterior chamber of the eye into the sub-conjunctival space; in doing so it is essential to avoid as far as possible all interference with the uveal tissue. The purpose of an iridectomy is to avoid the danger of the iris in the neighborhood of the wound being drawn and impacted in the trephined hole. We have found in a large number of cases in which an iridectomy has been omitted, that the results have been in no way inferior to those in which a piece of iris has been removed, provided always that no subsequent iris prolapse takes place. In pursuance of our purpose to avoid uveal tissue, we split the cornea, and place the trephine as far forward as such splitting will allow, and we bear on the trephine in such a way that it cuts through on the corneal edge of the wound first. This insures establishing our fistula in the most anterior position possible, and, therefore, as far away as possible from the ciliary body and the angle of the chamber. Third: The difficulties of the operation. Far too much stress has been laid on these. Trephining is an operation which can be performed by any surgeon who is used to ophthalmic manipulations, and who has good sight. It is essential that he should work in a good light. The necessary technique can be acquired from a written description. It is not for a moment necessary that the surgeon who wishes to learn trephining should see the originator of the operation at work. If, however, he feels diffident at undertaking the procedure until he has seen it done by another, there are many centers in this country where the operation is now being successfully performed. I would mention amongst those which I have visited New York, Minneapolis, St. Louis, Nashville, Louisville, Detroit and Chicago. I have seen results of trephining by American surgeons which could not be bettered anywhere.