The Haigis Formula

Abstract

AbstractThe Haigis formula, like other optical formulas, is based on thin lens optics. However, while all other formulas use only one constant (like the ACD constant, the A-constant, or the surgeon factor) for a given IOL, the Haigis formula uses three (a0, a1, and a2). In addition, apart from the axial length, the anterior chamber depth is taken to serve as a predictor for the postoperative IOL position. By this approach, it is possible to represent an IOL by a curve (optical ACD vs axial length) rather than a number. The power of the formula evolves after optimization with individualization of constants insofar as it allows a mean zero prediction error for the postoperative refraction irrespective of axial length. Although a classical optimization on the basis of one constant is possible, Haigis recommends optimization of the three constants, a0, a1, and a2, derived from a statistical analysis of postoperative results. Thus, for every intraocular lens, an individual curve is defined for optimum prediction of the postoperative IOL position allowing a mean zero prediction error for all axial lengths.