Estimation of intraocular lens position from full crystalline lens geometry: towards a new generation of intraocular lens power calculation formulas

Eduardo Martinez-Enriquez,Sonia Durán-Poveda,Ignacio Jiménez-Alfaro,Pablo Pérez-Merino,Susana Marcos

doi:10.1038/s41598-018-28272-6

Abstract

In a cataract surgery, the opacified crystalline lens is replaced by an artificial intraocular lens (IOL). To optimize the visual quality after surgery, the intraocular lens to be implanted must be selected preoperatively for every individual patient. Different generations of formulas have been proposed for selecting the intraocular lens dioptric power as a function of its estimated postoperative position. However, very few formulas include crystalline lens information, in most cases only one-dimensional. The present study proposes a new formula to preoperatively estimate the postoperative IOL position (ELP) based on information of the 3-dimensional full shape of the crystalline lens, obtained from quantitative eye anterior segment optical coherence tomography imaging. Real patients were measured before and after cataract surgery (IOL implantation). The IOL position and the postoperative refraction estimation errors were calculated by subtracting the preoperative estimations from the actual values measured after surgery. The proposed ELP formula produced lower estimation errors for both parameters -ELP and refraction- than the predictions obtained with standard state-of-the-art methods, and opens new avenues to the development of new generation IOL power calculation formulas that improve refractive and visual outcomes.

Highlights

Age-related cataract is a cause of blindness on a global scale (43% of worldwide blindness) due to biological aging, genetic, and environmental factors of the crystalline lens, which loses its transparency
Different generations of theoretical formulas have been proposed since 1970s, which vary in the way in which they estimate the lens position (ELP): the first generation assumed a constant value for the ELP5,7; the second generation individualized the prediction by replacing the constant estimated lens position (ELP) by one variable dependent on the axial length (AL) measured for every patient[6,11]; the third generation formulas (i.e. SRK/T formula[9], Holladay formula[8], or the Hoffer Q formula12) used axial length and anterior corneal curvature to predict ELP
We found a significant correlation between Lens Thickness (LT) and: Volume,VOL (r = 0.905, p = 5.1·10−5); Lens Surface Area, lens surface area (LSA) (r = 0.76, p = 0.004); Equatorial Plane Position, equatorial plane position (EPP) (r = 0.98, p = 2.5·10−9); Radius of the Anterior Lens, RAL (r = −0.66, p = 0.019); Radius of the Posterior Lens, RPL (r = −0.75, p = 0.0046), LSA/ VOL (r = −0.98, p = 1.5·10−8); Preoperative Anterior Chamber Depth, ACD preoperative (ACDpre) (r = −0.83, p = 8.5·10−4) and age (0.69, p = 0.013)

Summary

Introduction

Age-related cataract is a cause of blindness on a global scale (43% of worldwide blindness) due to biological aging, genetic, and environmental factors of the crystalline lens, which loses its transparency. Improvements in the ELP will provide better IOL power selection and refractive and visual outcomes. Fourth and fifth generations included the preoperative anterior chamber depth (ACD) to improve the prediction (Olsen[16] and Haigis formulas[10], respectively). In all of these approaches, the ELP is estimated from parameters unrelated to the shape of the crystalline lens. It seems reasonable that the estimation of where the IOL will be placed within the capsular bag will largely benefit from accurate 3-D information of the crystalline lens geometry

Methods

Results

Conclusion