It is an interesting fact that, although the textbooks of refraction and ophthalmic optics describe the use of the Maddox rod in the determination of imbalances of the extraocular muscles, they fail to explain how a cylindrical glass rod can make a light appear drawn out into a line perpendicular to the axis of the rod, and this despite the fact that the explanation is not difficult.
I have been able to find only two explanations in the English literature. The earlier one is by Fincham.1 He limited his explanation to a much too brief single sentence and then failed to demonstrate it in his accompanying drawing. A reader might well find it impossible to understand Fincham's statement. The second, and much longer, explanation is by Havener and Olesky.2 Although an accompanying photograph shows an excellent and correct optical model, their description seems obscured to me by a
EGGERS H. The Maddox-Rod Phenomenon. AMA Arch Ophthalmol. 1959;61(2):246-247. doi:10.1001/archopht.1959.00940090248009