"This exudation, or growth, as we might call it, went on from the edges of the iris until it met in the middle of the pupil. Then there was spread across the aperture of your lens an opaque granulated curtain through which light could not pass. Therefore you could not see. The plastic exudation had done its evil work as the result of the iritis--that is to say, of the sufferings of the iris." "I begin to understand," said Mary Gage. "That covers what seemed to happen." "It covers it precisely, for that is precisely what did happen. It was not cataract. I knew, or thought I knew, that it was not from retinal scars due to inflammation in the back of the eye. It was just a filling up of the opening of the eye. "So I know you lost sight in that last eye little by little, as you did in the other. You kept on knitting all the time. On your way out you struck the glare from the white sands of the plains in the dry country. At once the inflammation finished its exudation--and you were blind." She sat motionless. "Sometimes we take off the film of a cataract from the eye; sometimes even we can take out the crystalline lens and substitute a heavy lens in glasses to be worn by the patient." "But in my case you intend to cut out that exudation from the pupil?" "No. I wish we could. What we do is to cut a little key-hole aperture, not through the pupil, but at one side the pupil. In other words, I've got to make an artificial pupil--it will be just a little at one side of the middle of the eye. You will hardly notice it." "But that will mean I cannot see!" "On the contrary, it will mean that you can see. Remember, your eye is a lens. Suppose you put a piece of black paper over a part of your lens--paste it there. You will find that you can still make pictures with that lens, and that they will not be distorted. Not quite so much illumination will get into the lens, but the picture will be the same. Therefore you will see, and see finely. "Now, you must not be uneasy, and you must not think of this merely as an interesting experiment just because you have not heard of it before. My old preceptor, Fuller of Johns Hopkins, did this operation often, and almost always with success. He could do it better than I, but I am the best that offers, and it must be done now. "There is a very general human shrinking from the thought of any operation on the eye--it is so delicate, so sensitive in every way, but as a matter of fact, science can do many things by way of operation upon the eye. If I did not think I could give you back your sight, you may be sure I should never undertake this work to-day. The operation is known technically as iridectomy. That would mean nothing to you if I had not tried to explain it.