Advanced Optical Analysis of Divergence Between the Foci of the Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) and Aiming Beam Lasers.

ABSTRACT

Purpose: To evaluate the divergence between the neodymium-doped yttrium aluminum garnet (NdYAG) surgical laser and the aiming diode laser beams foci. Design: Optical analysis and measurements were performed using a Volk Goldmann 3-mirror lens with a Nidek YC-1800 NdYAG laser apparatus. Subjects: None. Methods: We used the Zemax OpticStudio program for the model of NdYAG treatment in a human eye. Additionally, theoretical calculations were performed. Main Outcome Measures: The divergence between the NdYAG laser focus and the intersection of the 2 aiming beams inside the eye. Results: Focal points of the 2 laser beams converge 8 mm behind the cornea. Posterior to this point, the intersection of the diode laser aiming beams lies in front of the focal point of the NdYAG treatment laser, with distance between the 2 foci progressively increasing up to 305 microns at 24 mm behind the cornea. Conclusions: We report the degree of divergence between the 2 lasers' focal points due to the difference in refraction between the corresponding wavelengths. These results have high practical relevance, as they provide a starting point for increasing the accuracy of NdYAG laser treatment, particularly when applied to the posterior segment, thereby minimizing the risk of complications. Current NdYAG laser devices have the built-in ability to modify the focal point of the aiming beam along the z-axis, thus providing possibility for an immediate application of our findings in clinical practice. Financial Disclosures The authors have no proprietary or commercial interest in any materials discussed in this article.