# Optical Forums > Optical and Ophthalmic Equipment >  Sadler box-o-graph

## lw0938

I have a Sadler Optical Box-O-Graph (11-2020) and I have no idea how to use it. I called EVERY supplier I could think of, and of course the place where I ordered it from.  Sadler web search showed no direct contact for them.  Anyone use this manual device or something like it to find an ED??

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## Don Gilman

> I have a Sadler Optical Box-O-Graph (11-2020) and I have no idea how to use it. I called EVERY supplier I could think of, and of course the place where I ordered it from.  Sadler web search showed no direct contact for them.  Anyone use this manual device or something like it to find an ED??


Closest you could get is to but the lens in diagonally to get a long point. To get an accurate ED you would have to trace the lens and box it to find the middle then double the longest radius from the center.

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