Correlations of Immediate Corneal Tomography Changes with Preoperative and the Elapsed Phaco Parameters

Abstract

Purpose: The ability to predict corneal edema and understand its relationship with imaging parameters enables optimization of decision-making in terms of cataract surgery. Therefore, we aimed to elucidate the immediate tomographic alterations after phacoemulsification.

Patients and methods: In this prospective study, we evaluated clinical and corneal tomographic data of 30 patients with cataracts, obtained using a rotating Scheimpflug tomographic system before and after cataract surgery with a phacoemulsification system. Corneal thickness and volume were measured, and Pentacam Nucleus Staging, keratometry, and specular microscopy were performed preoperatively and immediately postoperatively. The Wilcoxon signed-rank test was used to compare pre-and postoperative values. We calculated the correlations between the changes in these values and multiple parameters related to phacodynamics, including "ultrasound (US) elapsed" (phaco time), "US average" (average power used), and "US absolute" (energy effectively dissipated, a product of the other two parameters).

Results: There were increases in corneal volume (p<0.0001) and pachymetry (p<0.0001), and a decrease in endothelial cell count (p<0.0001) after surgery. The mean differences in pre- and postoperative specular microscopy, corneal volume, and pachymetry were -335.13±236.21 cells/mm³, 1.33±0.56 mm³, and 61.33±23.73 microns, respectively. The difference in pre-and postoperative corneal volume in patients with US elapsed ≥40 s was 0.75 mm³ greater than that in patients with US elapsed <40 s (95% confidence interval [CI]: 0.24-1.25; p=0.005); that of pachymetry in patients with US elapsed ≥40 s was 31.76 microns greater than that in patients with US elapsed <40 s (95% CI: 9.55-53.97; p=0.007). Spearman correlation revealed that, for every 1% increase in cataract density, the US average value increased by 0.31% (coef.: 0.3110; 95% CI: 0.0741-0.5490; p=0.012).

Conclusion: Knowledge of Pentacam Nucleus Staging and the effect of US elapsed on differences in corneal volume and pachymetry before and after cataract surgery should be of particular value for surgeons who routinely encounter patients with hard cataracts.

Keywords: cataract surgery; corneal volume; pachymetry; phacoemulsification; ultrasound.

Figure 1

Box plots for astigmatism, specular microscopy, corneal volume, and pre- and postoperative pachymetry.

Figure 2

Regression analysis showing a moderate linear correlation between US average and cataract density.