1.1 General information
From January 2017 to April 2019, the details of patients who underwent phacoemulsification combined with AcrySof Toric IOL implantation in Daqing Oilfield General Hospital, Heilongjiang Province, China were collected. The inclusion criteria were: 1) lens opacity, nuclear hardness grade III (Emery nuclear hardness grading standard); 2) corneal astigmatism was regular, and the degree of astigmatism was ≥ 1.50 D; 3) eye axis > 24 mm; 4) the preoperative data were complete, and a follow-up was completed 24–48 months after operation. Exclusion criteria were: 1) patients with other eye diseases (including eye trauma, keratoconus, glaucoma, macular degeneration and other retinopathies) that may affect the postoperative BCDVA and patients with a history of other eye surgery; 2) patients implanted with a capsular tension ring; 3) patients with intraoperative or postoperative complications; 4) patients who were participating in other clinical trials. This study adhered to the tenets of the Declaration of Helsinki. This study was approved by Institutional Review Board and Ethics Committee of the Daqing oilfield general hospital. All enrolled patients provided written informed consent to participate in this study.
1.2 Research methods
1.2.1 Preoperative examination: Routine examination was performed before cataract extraction. The preoperative BCDVA of all patients was determined by the same optometristby comprehensive optometry (TOPCON, Japan), and the AL, corneal astigmatism and corneal curvature were measured with the IOL Master 700 (Zeiss, Germany). If the AL could not be measured with the IOL Master 700, a super KR 8100 P (TOPCON) was used for supplementary measurement.
1.2.2 Related calculations of the Toric IOL: The spherical power of the Toric IOL was calculated by the Haigis formula and the cylindrical power was calculated by the Barrett formula. After logging in the website http://www.acrysoftoriccalculator.com and inputting the corneal curvature, incision position and surgical astigmatism, selection of the AcrySof Toric IOL T2–T9, the axial positional placement during the operation and the estimated residual astigmatism were obtained. The incision position was uniformly selected as 155° and the degree of surgical astigmatism was set at 0.30 D.
1.2.3 Preoperative positioning: The patient took a sitting position and the slit lamp band was turned with the axis alignment mark applied to the surgical incision and the axial direction of the intraocular lens, respectively. The slit lamp light passed through the center of the cornea, and a mark was made at the surgical incision position of the limbus of the cornea with a marker pen, while two marks were made in the axial direction of the IOL. All marking and operations were performed by the same doctor.
1.2.4 Operation method: The operation was performed by the same experienced physician, and the two groups of patients received the same operation method. Under the guidance of a Version navigation system, a 2.2 mm transparent corneal incision was made at a predetermined position, and the diameter of the capsulorhexis was 5.0–5.5 mm. A Centurion System (Alcon) was used in the operation to evacuate the turbid lens. Following Toric IOL implantation, it was adjusted clockwise to the predetermined axial position under the guidance of navigation, and the viscoelastic agent between the Toric IOL and posterior capsule was evacuated. Before the incision was closed with water, the needle was gently pressed down. Following the operation, levofloxacin, propranolol and dipyridamole eye drops were given, four times on one day a week for one month.
1.2.5 General postoperative data: The condition of the patients at the follow-up visit from 24 to 48 months, including intraocular pressure, observation of the cornea, posterior capsule of lens and fundus under the slit lamp, the BCDVA and residual astigmatism were recorded.
1.2.6 Rotation of the Toric IOL: Measurement by the slit lamp method was as follows at 1 hour and 24-48 months after surgery: After the pupil was fully dilated, the patient was instructed to keep the head level under the slit lamp with the axis alignment mark. The slit lamp band was overlapped with the Toric IOL axis and the degree on slit lamp was record. OPD-Scan III measurement was as follows: The patient was asked to blink three times then watch the cursor in OPD- Scan III instrument. The Toric IOL Summary mode was adjusted, the start button was pressed, the measured values were collected continuously for three times and the mean value was calculated. The position of the red line was on the axis position of the IOL. As shown in Figure 1, the Toric IOL was at 83°. The difference of IOL axis between 1 hour and 24-48 months after surgery was recorded.
1.2.7 Statistical methods: Statistical analysis was performed using SPSS 22.0 software. Continuous variables are expressed as the mean and standard deviation (X±SD). Continuous variables between the two groups were compared by t test, while categorical variables were compared by X2 test. P<0.05 was considered to be statistically significant.