Intraocular Lens Power Calculation Based On Ray Tracing Optimization: Predicting The Refractive Target In Post-Lasik Eyes

To predict the post-operative refractive error in cataract surgery eyes with previous corneal refractive surgery (LASIK) using ray tracing optimization technology. 

(1) Imec and Ghent University, Ghent, Belgium. (2) Miranza Begitek, Vitoria, Spain. 

A total of 75 eyes were included in the study, each with previous LASIK for either myopia (n=56) or hyperopia (n=19) followed by cataract surgery. Anterior and posterior corneal Zernike coefficients, axial distances and IOL geometry were exported to custom-developed algorithms where the patient-specific eye models were built. Optical quality was described in terms of the metric Visual Strehl (VSOTF). The defocus and astigmatism producing the maximum VSOTF was taken as the optimal target and compared with the post-operative subjective refraction (power vectors: M, J₀ and J₄₅). The estimated IOL power (Ray Tracing Optimization, RTO) was compared with the Barret True K no history method. 

The RTO method showed the lowest mean absolute prediction error (p<0.05) and the highest percentage of eyes within ±0.5D and ±1.0D (p<0.05). The RTO had a smaller standard deviation than the Barrett True K no history method (0.51D vs. 0.87D) and the range was also considerable smaller for RTO (2.875D vs. 5.25D). The Bland-Altman analyses showed high reliability between the predicted refraction (RTO) and the post-operative subjective refraction. The percentage of eyes within ±0.5D was of 82.6% (M), 84.1% (J₀) and 82.6% (J₄₅), while the agreement within ±1.0D was of 93.3% (M), 98.6% (J₀) and 97.3% (J₄₅).

Ray tracing optimization presented high degree of precision in the refraction estimation of post-LASIK eyes.