Numerical model of refractive-index writing inside an intraocular lens at a laser wavelength of 1550 nm
Uliana S. Averkieva1, Stanislav G. Sazonkin1, Ilya O. Orekhov1, Kirill B. Pershin1, Sergey I. Kudryashov1,2, Nikita A. Smirnov1,2, Petr P. Pakholchuk1,2, Alexey V. Gorevoy1,2, Yulia S. Gulina1,2, Elena N. Rimskaya1,2, Pavel A. Danilov1,2, Alexander Yu. Tsygankov1,2;
1Bauman Moscow State Technical University, Moscow, Russia;
2P. N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, Russia
Abstract
Cataract treatment typically involves implantation of an intraocular lens (IOL), whose optical power is calculated from biometric measurements. However, the target postoperative refraction is achieved within ±0.5 D in only 61–88% of cases. Residual refractive error is usually corrected with spectacles or by secondary IOL exchange. Laser-induced microstructuring of an implanted IOL may enable noninvasive refractive correction, although suitable writing parameters are still selected mainly empirically.
This study presents a numerical model of refractive-index modification in a hydrophobic acrylic IOL exposed to 1550 nm laser radiation. The model incorporates six-photon absorption, pulse-number-dependent reduction of the modification threshold, cumulative heating, and the dependence of refractive-index change (Δn) on radiation dose.
An erbium fiber laser was modeled with repetition rates of 0.67–13.3 MHz, pulse energies of 49–161 nJ, pulse durations of 9–28 ps, and a beam waist radius of 2.7 μm. At 13.3 MHz, pulse energies above approximately 60 nJ increased the material temperature beyond 250 °C, causing damage, whereas at 3.35 MHz the temperature remained below 200 °C. Structures composed of 25 dots, 13 lines, and 7 rings produced Δn values up to 3.5 × 10⁻³ within a 30 μm layer. Lens power remained effectively unchanged (|ΔP| < 10⁻⁴ D), while the modulation transfer function at 100 mm⁻¹ reached the diffraction limit of 0.62. The model enables prediction of refractive-index modification, thermal damage, and image quality for specified laser parameters.
Speaker
Uliana Averkieva
Bauman Moscow State Technical University, Moscow, Russia
Russia
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