The Rise And (Near) Fall Of The Vergence Approach For Iol Calculations: When Fedorov Was Wrong

One of the most influential papers in the history of cataract surgery is Fedorov and Kolinko’s 1967 paper. All so called third and fourth generation intraocular lens calculation formulas implemented to this day are based on it.  We show that the actual expression in the 1967 article is incorrect and was subsequently corrected by Fedorov and colleagues in 1975.  We show the source of error and comment on implications for modern day intraocular power calculations for cataract surgery.  To our knowledge, there is no systematic comparison that has been attempted between the 1967 and 1975 versions of Fedorov and colleagues’ articles.  In fact, a number of key papers have cited both the 1967 and 1975 articles without mention of any discrepancy.

Private Clinical and Surgical Practice and Research Center.   Analysis of original papers on the vergence method for IOL calculation and half a century of variations on the vergence method for IOL power calculations along with corresponding citation history.

We compare the 1967 version of Fedorov IOL power formula appearing in the Russian literature and considered to be the earliest vergence optic based formula to the 1975 version that appeared much later in the English literature (1975).  We take the difference between the two formulae and explore the implications.     

Fedorov 1967 turns out to be diffferent from Fedorov 1975. After aligning the correspondig variables the difference is revealed to be non-zero.   The analytical investigation revelas the error to be in the 1967 paper itself and not in the cited sources.   The error difference infuence on the reported clinical cases is analyzed in the light of the authors' comments on the target refraction.

Fedorov and Kolinko’ foundational equation as formulated in 1967 is profoundly insightful, influential and yet incorrect.  The apparent lack of awareness or mention of the differences between the 1967 version and the 1975, for half a century is stunning!  Fedorov and Kolinko's work constitutes one of the pillars of a paradigm shift that, along with high quality intraocular lenses delivered through smaller incisions, moved cataract surgery from a risk prone procedure with moderate outcomes to one of the most sophisticated and successful procedures in the history of Medicine.  Fully understanding and analyzing giants’ mistakes, as we do  here, is a most valuable tool for our pursuit of excellence in cataract refractive surgery.