The effect of corneal tunnel length in patients after standard phacoemulsification through a 2.75 mm incision on surgically induced astigmatism, corneal thickness and endothelial cell density

Abstract

Purpose: The purpose was to determine the effect of the corneal tunnel length in the 2.75 mm wide clear corneal incision, created during phacoemulsification on surgically induced astigmatism, central corneal thickness and corneal endothelial cell loss.

Material and methods: The study comprised 27 eyes (27 patients) who underwent phacoemulsification through 2.75 mm temporal clear corneal incision. Patients were examined preoperatively, 1 day, 7 days and 1 month postoperatively. Exclusion criteria were: previous intraocular surgery, corneal disorders and previous ocular trauma. Best corrected distance visual acuity, keratometry, slit-lamp examination, anterior segment optical coherence tomography and corneal endothelial cell density measurement were performed. Surgically induced astigmatism was calculated with vector method. Statistical analysis was done using non-parametric tests: Wilcoxon test, Mann-Whitney U test and Spearmann correlation coefficient.

Results: Mean best-corrected distance visual acuity was 0.30±0.24 preoperatively and 0.94 ± 0.18 postoperatively (p<0.05). Mean corneal incision length 1 day postoperatively was 1.84±0.36 mm. Surgically induced astigmatism was 0.51 ± 0.41 D one month postoperatively. Clear corneal incision length and surgically induced astigmatism were positively correlated (p<0.05). Mean central corneal thickness was 0.51 ± 0.05mm preoperatively, 0.56± 0.09 mm one day and 0.51 ±0.05 mm one month postoperatively (p <0.05). Clear corneal incision length and central corneal thickness 30 days postoperatively were not corrdlated (p=0.27). Mean corneal endothelial cell density was 2483?417 cells/mm² preoperatively and 2325 ± 410 cells/mm² postoperatively. The difference was significant (p<0.05). Clear corneal incision length and corneal endothelial cell loss were not correlated (p>0.05).

Conclusions: The results suggest that the length of the 2.75 mm clear corneal incision influences the surgically induced astigmatism, but it doesn't influence the central corneal thickness and corneal endothelial cell loss. Shorter clear corneal incisions induce smaller surgically induced astigmatism in comparison with longer incisions of the same width and localization. Unequivocal confirmation.of the influence of clear corneal incision length on surgically induced astigmatism requires further investigation on a larger group of patients. Using laser techniques could help, as it would enable to examine patients in groups with different predefined clear corneal incision lengths.