A varifocal has three prescriptions blended into one lens: distance at the top, intermediate in the middle, reading at the bottom. The blending is the hard part, and it is where every price difference comes from.
Between the distance zone and the reading zone runs a channel of usable vision called the corridor. Either side of it, the optics are distorted, because the lens has to get from one power to another somehow and the distortion has to go somewhere. A cheap varifocal has a narrow corridor and wide areas of blur. An expensive one has a wide corridor and narrow blur.
Reading a book is a narrow task: your eyes sit still and low. A monitor is wide and at arm’s length, which is exactly the intermediate zone, exactly where a standard corridor is narrowest. If you spend the day at a screen, the wide corridor lens is the one upgrade in this practice that we push, and it is the only one.
Most people adapt within two weeks. Wear them full time, look through the bottom to read rather than tipping the page, and expect the floor to feel odd on stairs for a few days. If you are still fighting them at four weeks, they are wrong, not you.
That is why we remake within thirty days at no charge, in a different design or as single vision. About one person in twenty needs it, which is too many to treat as the patient’s problem.
