[Shifts in the diameter of continuous circular capsulorhexis based on the Gullstrand eye model with the Callisto Eye System during cataract surgery].

Objective: To investigate the disparity between the set value of the capsulorhexis ring diameter in ophthalmic surgical navigation systems and the actual capsulorhexis ring diameter projected onto the lens surface. Methods: It was a cross-sectional study. Based on the Gullstrand eye model, the theoretical diameter of the capsulorhexis ring projected onto the lens plane through the cornea was calculated using the law of refraction in the Callisto Eye System. When the anterior chamber depth (ACD) ranged from 2.0 to 4.0 mm and the corneal curvature ranged from 40.00 to 48.00 D, the capsulorhexis ring diameters were calculated after projecting capsulorhexis rings with set diameters of 5.5 mm and 6.0 mm onto the lens plane. Additionally, 40 patients (40 eyes) aged 40 to 85 years who underwent cataract phacoemulsification combined with intraocular lens implantation at the Sixth People's Hospital of Shanghai Jiao Tong University School of Medicine were selected to validate the theoretical calculations. Among them, 15 were male, and 25 were female, and they were divided into three groups based on the ACD: group A (13 eyes) with ACD<3.0 mm; group B (16 eyes) with 3.0 mm≤ACD<3.5 mm; group C (11 eyes) with ACD≥3.5 mm. One week after surgery, anterior segment images of the eyes were taken, and the actual capsulorhexis ring diameter was measured using the Photoshop image processing software and compared with the set and calculated values. Results: When the capsulorhexis ring diameters were set at 5.5 mm and 6.0 mm and the corneal curvature was calculated based on the Gullstrand Eye model at 43.05 D, a linear negative correlation was found between ACD and the capsulorhexis ring diameter projected onto the lens plane ( P <0.001). When the ACD was set at 2.5, 3.0, and 3.5 mm, and the capsulorhexis ring diameters were set at 5.5 and 6.0 mm, a linear negative correlation was observed between corneal curvature and the capsulorhexis ring diameter projected onto the lens plane ( P <0.001). When the capsulorhexis ring diameter was set at 5.5 mm and the patient ACD and corneal curvature data were used for calculations, the capsulorhexis ring diameters projected onto the lens plane for groups A, B, and C were (5.09±0.05) mm, (4.97±0.05) mm, and (4.91±0.07) mm, respectively. When the capsulorhexis ring diameter was set at 6.0 mm, they were (5.56±0.05) mm, (5.44±0.05) mm, and (5.37±0.08) mm, respectively. One week after surgery, the actual measurements of capsulorhexis ring diameters for groups A, B, and C were (5.44±0.20) mm, (5.27±0.28) mm, and (5.25±0.41) mm, respectively, and the differences compared to the calculated values were not statistically significant (all P >0.05), but the differences compared to the set values were statistically significant (all P <0.001). Conclusion: The capsulorhexis ring diameter projected onto the lens surface by the Callisto Eye system was reduced by 7.33% to 10.48% compared to the set value, and the degree of reduction increased with the increase of ACD and corneal curvature.