Subjects
A prospective, observational cohort study was carried out on consecutive patients who underwent ICL V4c implantation in the Department of Eye & ENT Hospital of Fudan University from April 2015 to May 2017. The study is adhered to the Declaration of Helsinki and was approved by the Ethics Committee of the Eye & ENT Hospital Hospital, Fudan University, China. All patients provided signed informed consent after a detailed explanation of risks and potential outcomes of the implantation and the study.
The baseline characteristics and preoperative biometric values of the patients are shown in Table 1. The study enrolled 51 eyes of 31 patients (4 men and 27 women, 36 ICLs and 15 Toric ICLs) with a mean age of 32.45 ± 6.85 years old. All patients underwent routine preoperative examinations and met the surgical indications of ICL implantation for the correction of high myopia. The inclusion criteria were: age between 20 and 45 years old, spherical refraction of more than − 6.00 D, astigmatism of up to − 5.00 D, corrected distance visual acuity (CDVA) of 20/200 or better, and ACD of < 2.80 mm. The exclusion criteria includes a history of ocular conditions other than myopia (suspicion of keratectasia, cornea or lens opacity, retinal detachment, glaucoma, macular degeneration, or neuro-ophthalmic disease) with or without astigmatism, a history of ocular surgery, inflammation or trauma, any chronic systemic disease, and an endothelial cell count < 2000 cells/mm2.
ICL V4c
The ICL V4c (STAAR Surgical, Nidau, Switzerland) corrects −0.50 D to − 18.00 D myopic spherical refraction and up to − 5.00 D cylindrical refraction. There are 4 sizes: 12.1 mm, 12.6 mm, 13.2 mm, and 13.7 mm. Power calculation of the ICL V4c was performed as per the manufacturer using a modified vertex formula, according to the provided preoperative refractive parameters. The size of the implanted ICL V4c was determined based on the white-to-white horizontal corneal diameter and ACD. Toric ICL V4c is designed to correct both spherical and cylindrical diopters.
Surgical technique and follow-ups
All implantations were performed by two experienced surgeons (XZ and XW). The surgical technique has been previously described by Chen X et al [12]. Briefly, pupils were dilated before surgery. After injection of 1% sodium hyaluronate into the anterior chamber via a puncture site at the 6 o’clock position of the cornea, an ICL V4c was implanted via a 3.0 mm temporal corneal incision using an injector cartridge and then was placed in the posterior chamber. After that, the viscoelastic surgical agent was completely removed using a balanced salt solution, and a miotic agent was instilled. After the surgery, patients were given 1% tobramycin dexamethasone for 3 days followed by 0.1% fluorometholone (tapered gradually over 2 weeks), 0.5% left ofloxacin for 1 week, non-steroidal anti-inflammatory (NSAID) eye drops for 2 weeks, and artificial tears for 1 month.
All the patients were followed at 1 day, 1 week, 1 month, 6 months,12 months and 24 months after the surgery. The mean follow-up time was 15.35 ± 4.90 months (ranges from 12 to 25 months). Routine measurements before and after the surgery include: decimal of uncorrected distance visual acuity (UDVA), decimal of corrected distance visual acuity (CDVA), manifest refraction (spherical equivalent, SE), anterior chamber depth (ACD; Pentacam, Oculus, Germany; measured from the corneal endothelium to the anterior lens), endothelial cell density (ECD; noncontact specular microscopy, SP-2000P, Topcon Corporation, Japan), intraocular pressure (IOP; non-contact tonometer, Canon, Japan), axial length (IOL master, Carl Zeiss, Germany), standard slit-lamp biomicroscopic and funduscopic examinations, central corneal thickness (Pentacam), horizontal corneal diameter (white-to-white, WTW; IOL master) and ultrasound biomicroscopy (UBM; Quantel medical, France)
Statistical analysis
Refractive outcome graphs were plotted using Microsoft Excel according to the refractive outcomes at 1 month, 6 months,12 months and 24 months in the patients. All statistical analyses were performed using the software Statistical Package for the Social Sciences (SPSS) Version 20.0 (SPSS, Chicago, IL, USA). The Kolmogorov–Smirnov test was used to determine if a variable is normally distributed. The results were expressed as the mean ± standard deviation (SD). According to each variable’s distribution, a paired t test or Wilcoxon signed-rank test was choosed to compare the parameters between time points and p < 0.05 was considered statistically significant. Statistical analysis for visual acuity was based on Decimal units.