The Effect of Hydrodynamic Parameters on Corneal Endothelial Cell Loss After Phacoemulsification

Patients aged 50 to 70 years old with moderate lens opacities (nuclear sclerosis of 3+) were included. The exclusion criteria were: 1-previous corneal pathology (dystrophic or degenerative such as Fuchs' endothelial dystrophy or advanced trachoma), 2- pseudoexfoliation syndrome (PEX), 3- history of intra ocular surgery, 4- glaucoma or ocular hypertension, 5- eyes with a history of anterior uveitis, 6- diabetes mellitus, 7- anterior chamber depth (ACD) less than 2.5 mm or more than 4 mm, 8- axial length less than 21 mm or more than 25 mm, 9- density of endothelial cells less than 1500 cells per mm2, 10- polymegatism (CV > 0.4), 11- keratometric astigmatism more than 1.5 Diopters (D), 12- history of contact lens usage, 13- Intra-operative complications (posterior capsule rupture with or without vitreous loss), 14- postoperative uveitis, 15- postoperative surgical wound leakage, 16- deep-set eye, and 17- size of dilated pupil less than 6 mm. Nucleus density was evaluated using the LOCS III classification system Patients were divided in 2 groups randomly: Group 1 included those candidates for phacoemulsification using high hydrodynamic parameter: 400 mmHg vacuum and 40 ml/min flow rate (high vacuum technique) whereas group 2 consisted of patients who underwent phacoemulsification using low hydrodynamic parameters: 200 mmHg vacuum and 20 ml/min flow rate (low vacuum technique). All surgeries were performed by one surgeon using stop and chop technique with sovereign (white star technology) (AMO, USA). During sculpting stage, vacuum was 40mmHg and flow rate is 20ml/min, in both groups. Irrigation aspiration of cortical material and viscoelastic were bimanually and semi automatically performed with flow rate of 30ml/min.

Total ultrasound power and total volume of BSS in both groups were measured. Pachymetry, endothelial cell density, polymegathism, before and 1, 6 and 12 weeks after intervention were also evaluated. Statistically analysis of data included univariate (student t-test and x2) and multivariate (regression model) analysis of postoperative results.