Original Maddox Rod 1893
Original Maddox rod is named after E.E.Maddox, M.D. an English ophthalmologist. It was invented around 1890. The model here was the original. It consisted of one clear glass cylinder inserted into an opaque disc. This disc would then be inserted into a trial frame. When a small source of light is then shown to the patient, he will observe a streak of light at right angles to the axis of the cylinder orientation.
This original Maddox Rod was replaced within the decade by another model which featured several cylinders lined up in parallel as shown in the image. Later this was converted to red tinted cylinders. This was done to make the patient more able to identify the “red line” and separate it from the “point of light”. By doing the Maddox rod test, one could determine the amount of phoria (resting eye muscle drift) that a patient has.