Refractive Changes After Implantation of Reversed Intraocular Lens in Cataract Surgery: A Mathematical Model

Purpose: To develop a mathematical model that can predict the amount of refractive change caused by implantation of an intraocular lens (IOL) in a reversed position during cataract surgery. Methods: A theoretical mathematical formula based on the Gullstrand eye model was constructed to estimate the refractive change of the eye after implantation of a reversed IOL. The refractive change caused by implantation of the IOL in a reversed position was calculated based on the exchange of the anterior curvature with the posterior curvature of the IOL, and the lengthening of the distance between the IOL and the retina. In case of a three-piece IOL with angulation, the amount of refractive change was calculated based on its angle and the total refractive power of the eye, which is dependent on the focal length of the eye. Results: Calculated refractive change for one-piece IOLs was less than 0.10 diopter (D). For three-piece IOLs, the calculated refractive change makes the eye on average 0.77 D more myopic and can increase with the total refractive power of the patient's eye. The mathematical model was applied to seven previously published cases of reverse IOL implantation. Conclusions: This calculation demonstrates that with an upside-down IOL, there is a small refractive change in the one-piece IOL, including a toric IOL without angulation, but there can be a large refractive change in the three-piece IOL with angulation, especially using a higher power IOL or with a shorter axial length. [ J Refract Surg . 2023;39(5):326–331.]