Influence of Anterior Chamber Depth, Lens Thickness, and Corneal Diameter on Intraocular Lens Power Calculation

The main IOL power formulas are described along with the input variables used by each of them to predict the IOL position and the refractive outcomes reported by published studies. An overview of measurements techniques of anterior chamber depth, lens thickness, and corneal diameter is given. The impact of these variables is illustrated for the Barrett Universal II, EVO, Haigis, Hill-RBF, Hoffer Q, Holladay 1, Holladay 2, Kane, Olsen, PEARL-DGS, and SRK/T formulas. With formulas that do not take the anterior chamber into account, eyes with a deeper anterior chamber are more likely to experience a hyperopic outcome compared to eyes with a shallow anterior chamber. With most formulas, a tendency toward a myopic shift occurs with thin lenses and toward a hyperopic shift with thick lenses. Corneal diameter has a minimal effect on IOL power calculation.