This study was approved by the ethical committee of Affiliated Hospital of Nantong University. All procedures adhered to the tenets of the Declaration of Helsinki. All patients were willing to volunteer for the research and signed a written informed consent.
Thirty-six patients with cataract (39 eyes) who underwent routine phacoemulsification with AcrySof Toric IOL (Alcon Laboratories, Inc., Fort Worth, TX, USA) implantation between May 2018 and August 2018 were enrolled. All patients have regular corneal astigmatism between 1.0 D to 3.0 D. They did not have any eye diseases including corneal diseases, glaucoma, pterygium, ocular trauma, capsular calcification and abnormities of suspensory ligament. Patients with intraoperative or postoperative complications also were ruled out.
Routine preoperative examinations were performed for each patient in the study, including uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), slit-lamp biomicroscope examination, intraocular pressure, corneal topography (Pentacam HR; OCULUS Optikgeräte, Wetzlar, Germany), B-scan ultrasonography, IOL spherical power calculation (SRK/T formula from Lenstar LS900, Haag-Streit, Switzerland). Online Toric calculator software (Alcon, Inc., accessible at http://www.acrysof toriccalculator.com) was utilized to calculate the IOL cylinder power, taking into account keratometry data (total corneal curvature from Pentacam), SIA and the position of the incision.
Half hour before the surgery, the location of incision and axial position of IOL were marked on the cornea closed to the limbus using a sterile marker pen under the slit beam in the slit lamp. The patient should sit at the slit-lamp biomicroscope with head straight in the chin-rest and eyes focusing horizontally ahead.
Phacoemulsification was performed by one experienced surgeon(HJG) according to our previous research. All patients were implanted an AcrySof SN6A Toric IOL (T2–T8, Alcon). Before incision hydration, we created a pair triangular incision on anterior capsulotomy edge aligning the axial mark on optic of the IOL(Fig.1). The post-operation therapies were tobramycin and dexamethasone (Tobradex; Alcon, USA) and diclofenac sodium eye drops (Difei, Qixin Pharmaceutical, China) three times a day for 2 weeks.
Postoperative examinations were conducted 1 and 3 months after surgery to assess Toric IOL rotation. The photos were taken when the diameter of pupil was no less than 6 mm under slit-lamp biomicroscope.
The photographs were analyzed using tools in Adobe Photoshop (version 7.0). Using the “survey tool”, a straight line vertically crossed the center of pupil as the axis of 90 degree (Line1, Fig.2). Straight line by connected axial mark on optic of the IOL showed the actual astigmatic axis right now (Line2, Fig.3). Straight line by connected two triangular markers in the anterior capsule showed the astigmatic axis put in the surgery (Line3, Fig4). Through line1, line 2 and the calculated astigmatic axis before surgery, we had the theoretical rotation. Through line 2 and line 3, we had the actually rotation of the IOL. Every line was made three times to take the mean value.
SPSS version 17.0 was used for statistical analysis. Measurement data were shown in form of mean ± SD; Variance analysis was performed to compare the differences between two groups. P value <0.05 was considered for statistical significance.