The influence of corneal tunnel length on surgically induced astigmatism after various types of microincision phacoemulsification.

Purpose: To evaluate the influence of the corneal tunnel length on surgically induced astigmatism (SIA) after 3 phacoemulsification techniques.
Methods: Patients who underwent a planned phacoemulsification surgery with an implantation of a foldable, acrylic IOL were selected for the study. All surgeries were performed under topical anaesthesia, with the same phaco machine. Group I consisted of 30 eyes of 30 patients after bimanual 1.4 mm microincision cataract surgery (B-MICS). Group II consisted of 30 eyes of 30 patients after coaxial 1.8 mm microincision cataract surgery (C-MICS). Group III consisted of 30 eyes of 30 patients after coaxial 2.4 mm small incision cataract surgery (C-SICS).Best corrected visual acuity, autorefractometry, tonometry, a slit lamp examination and anterior segment OCT were performed preoperatively and 1, 7, 30 and 90 days postoperatively. The temporal peripheral corneal thickness and the chord length of the main incision were measured. Vector method was used to calculate SIA.
Results: Mean preoperative BCVA was 0.52 ± 0.19 and it improved to 0.98 ± 0.05 (p < 0.05). Mean corneal tunnel chord length was 1.30 ± 0.16 mm 90 days postoperatively in group I, 1.30 ± 0.19 mm in group II and 1.48 ± 0.22 mm in group III. SIA was 0.54 ± 0.48 mm in group I, 0.45 ± 0.21 mm in group II and 0.62 ± 0.30 mm in group III. There were no correlations between the chord length of the corneal tunnel and SIA calculated with using vector analysis method.
Conclusions: Unlike the incision width, the length of the clear corneal tunnel in small incisions and microinicions, has no significant influence on SIA.