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http://dx.doi.org/10.1016/j.ophtha.2009.06.020

has been cited by the following article:

• TITLE: Optimization of the A Constant for the SRK/T Formula

  AUTHORS: John C. Merriam, Eva Nong, Lei Zheng, Malka Stohl

  KEYWORDS: Cataract Surgery, SRK/T, A Constant

  JOURNAL NAME: Open Journal of Ophthalmology, Vol.5 No.3, August 5, 2015

  ABSTRACT: Purpose: To evaluate the effect of axial length (AL) and the average preoperative keratometry (K) on the A constant in the SRK/T formula. Methods: The retrospective, comparative case series includes 635 eyes from 407 cataract patients from Columbia University Medical Center from January 2006 to August 2010, operated by a single surgeon using a temporal incision and the Acrysof SN60WF IOL (Alcon Laboratories, TX). Using the postoperative manifest refraction and biometry data, we calculated the precise A constant (Ap) necessary to yield the postoperative spherical equivalent for each eye. To optimize the A constant, we developed three regression models (linear, quadratic, and categorical in 7 AL groups) to relate these precise A constants to AL and K. We verified our method with another series of 45 eyes for which we calculated mean errors (defined as the difference between the spherical equivalent of the postoperative refraction and the predicted postoperative refraction) using the optimized and manufacturer’s suggested A constants. Results: There is a statistically significant relationship between AL (P