I spent some time today at the Eye Clinic at the local hospital and I don't have to have an eye operation. I'll be having 15 prisms incorporated into the lenses of my new specs in three months time though. If my requirement had been anything over 20 prisms, then I'd have been under the knife for an operation with a 50-50 chance of success or total failure, and no chance of another one. I guess I'd rather have prisms than take a chance on having eyesight worse than I started with.