"Twenty years ago, I had the honour of submitting to this Society a statement of the effects of a mal-formation in my own left eye. The nature of the effect was this: that the rays of light coming from a luminous point and falling upon the whole surface of the pupil do not converge to a point at any position within the eye, but converge in such a manner as to pass through two lines at right angles to each other, (a geometrical phenomenon, to which the term astigmatism was very happily affixed by the present Master of Trinity College [Whewell])" (OED).