Comparison of fluid flow between bimanual and coaxial phacoemulsification using computational fluid dynamics

Background: To describe the fluid flow in the chamber of the eye during bimanual and coaxial phacoemulsification using computational fluid dynamics. Methods: Based on the human eye, a computerized eye model was developed. The fluid flow was modeled using the Navier–Stokes formula, turbulence modeling, and Boolean operations numerically. Several parameters of the flow field were evaluated and compared for both phacoemulsification methods. Results: Bimanual cataract surgery produced better followability than coaxial cataract surgery. However, bimanual cataract surgery increased the probability of posterior capsule fluctuation and chamber collapse. Conclusions: Bimanual phacoemulsification improves followability; however, it also increases the probability of posterior capsule rupture and chamber collapse. These findings suggest that there are both advantages and disadvantages to consider when using bimanual phacoemulsification. Keywords: Bimanual phacoemulsification; Coaxial phacoemulsification; Computational fluid dynamics; Followability; Posterior capsule rupture; Chamber collapse.

Corneal Higher-Order Aberrations after Phacoemulsification: A Comparison of 3 Different Incision Sizes

Purpose To analyze the impact of different incision sizes for phacoemulsification on corneal higher-order aberrations (HOA). Methods Patients seeking cataract surgery were randomly assigned to one of the following groups: 1.4 mm with biaxial microincision phacoemulsification (25 eyes), 1.8 mm with coaxial phacoemulsification (27 eyes), and 2.2 mm with coaxial phacoemulsification (62 eyes). Inclusion criteria were a minimum age of 18 years and uncomplicated cataract. Exclusion criteria were history of ocular trauma or intraocular surgery, any sign of inflammation or infection, pseudoexfoliation syndrome, glaucoma, optic atrophy, diabetic retinopathy, lens dislocation, cataracta intumescens, cataracta matura, and corneal diseases. Patients underwent phacoemulsification with implantation of an intraocular lens. Aberrometry was performed using an iTrace aberrometer with a pupil scan size of 5.0 mm preoperatively and at postoperative follow-up visits after 1 month. The paired sample t test and analysis of covariance were used for statistical analysis. Results Ninety patients (114 eyes) were enrolled (mean age 73.7 ± 8.9 years). In all groups, an increase of total HOAs could be measured. The strongest increase was seen in the 2.2 mm group (mean difference 0.031 [95% confidence interval (CI) 0.006-0.056], p = 0.014) and in the 1.4 mm group (mean difference 0.035 [95% CI -0.007 to 0078], p = 0.097). No important difference was found in the 1.8 mm group. Conclusions The 2.2 mm and the 1.4 mm incisions seem to have a higher impact on corneal HOAs in comparison to the 1.8 mm incision.