Ethical approval

According to the Helsinki Declaration, the study was approved by the ethics committee of Aier Eye Hospital, Jinan University (No. GZAIER2023IRB25; China Clinical Trial Record No. MR-44-24-009241). All subjects read and signed the informed consent form before participating in this study.

Study designs and patients

The study is a prospective observational clinical study. Patients who underwent ICL surgery from September 2022 to June 2023 and non-surgical patients during the same period were included and enrolled into surgery group and non-surgery group.

Inclusion criteria for surgery group

(1) The patients themselves have the desire to improve their refractive status by ICL surgery; (2) Myopic patients with refractive error not less than − 6.00 D, or eye axis ≥ 26 mm; relatively stable (refractive error change ≤ 0.50 D per year for 2 consecutive years); (3) Central anterior chamber depth ≥ 2.8 mm; (4) Corneal endothelial cell density ≥ 2,000 cells/mm2; (5) No progressive clouding of the lens; (6) No uncontrolled glaucoma; (7) No cone cornea, severe dry eye, active ocular lesions or infections; (8) No history of diabetes, hypertension, autoimmune disease, hematologic disease, systemic connective tissue disease or other systemic diseases, and no history of taking related medications; (9) Normal retina or retinal tear who has undergone retinal laser photocoagulation; (10) No history of eye surgery or trauma; (11) Age above 21 years old; (12) The patient is willing to cooperate with the follow-up observation.

Inclusion criteria for non-surgery group

Patients who meet the above items (2) to (12) but have no intention to undergo ICL/TICL surgery within six months for the time being.

Exclusion criteria

(1) Patients who are mentally or psychologically abnormal, unable to understand the risks of surgery or have unrealistic expectations; (2) Those who are unable to complete follow-up; (3) During pregnancy or breastfeeding.

Notably, high myopia significantly complicates the diagnosis of glaucoma, leading to a notable percentage of misdiagnoses. Research indicates that approximately 25–40% of patients with high myopia may be misdiagnosed with glaucoma due to overlapping symptoms and structural changes in the ONH and retinal RNFL caused by myopia itself [14, 15]. Therefore, during the consultation, we thoroughly inquired about the past medical history, family history, and medication history related to glaucoma, and monitored and recorded the intraocular pressure of each patient to ensure no misdiagnosis occurred.

Mainly outcomes.

The primary research outcomes encompass trabecular-iris angle (TIA), angle opening distance (AOD), vault height, angle recess area (ARA), and trabecular-iris space area (TISA) measured at 250/500/750µm distances using anterior segment OCT (Casia2, TOMEY, Japan). And FAZ area, choroidal thickness (CT), SVD (6 × 6 mm), DVD (6 × 6 mm), optic disc blood flow density (4.5 × 4.5 mm), and retinal nerve fiber layer thickness (RNFL) measured using fundus OCTA (RTVue XR Avanti, Optovue Inc., Fremont, CA, United States). The secondary research outcomes including visual acuity and intraocular pressure.

Preoperative and postoperative examinationsRoutine examination

All patients in the surgery group underwent routine preoperative examinations, including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), computerized refraction, cycloplegic refraction, non-contact intraocular pressure (IOP), slit-lamp examination, corneal topography, corneal biomechanics, axial length (AL), central corneal thickness (CCT), ultrasonic biologic microscopy (UBM), corneal endothelial cells, and scanning laser ophthalmoscopy (SLO). UBM was not performed in the non-surgery group because it was a contact examination, with all other routine examinations being the same as the surgery group.

AS-OCT, OCT and OCTA examination

All patients underwent AS-OCT examination, which was done by the same skilled technician who had received standard training and passed the examination skills test for the relevant instrument. Anterior chamber angle structural parameters such as AOD, ARA, TIA, and TISA measured at 250, 500, and 750 μm were recorded (Supplementary Fig. 1).

All patients underwent OCT and OCTA examinations, which were performed by the same skilled technician who had received standardized training and passed the relevant instrumental examination skills test. Angio Retina (3 × 3 mm), HD Angio retina (6 × 6 mm), Grid, ONH and Angio Disc modes were selected for scanning respectively. Images with an imaging quality score > 6 or clear as a slice were selected for inclusion in the analysis. FAZ area, CT, SVD, DVD, RNFL thickness and disc retinal perfusion capillary vessel density (DRVD) were recorded (Supplementary Fig. 2).

CT measurements were taken from the outer edge of the RPE layer to the inner edge of the choroidal layer, averaging horizontal and vertical orientations at the macular central sulcus nadir, as shown in Supplementary Fig. 3a. FAZ area was measured in Angio Retina (3 × 3 mm) mode, spanning from 10 μm below the inner border membrane to 10 μm above the outer plexiform layer, as shown in Supplementary Fig. 3b. DRVD measurements were based on the percentage of the area occupied by the vascular system of the RPC plate, from the inner border membrane to the nerve fiber layer, as detected in HD Angio Disc mode, as shown in Supplementary Fig. 3c. The built-in software of the OCTA performs layered segmentation and calculation on the image.

The RNFL thickness was obtained based on ONH scanning measurements within a 3.4 mm diameter circle centered on the optic disk, as shown in Supplementary Fig. 4.

Surgical procedure and postoperative medication

All surgeries were performed by the same experienced surgeon (Z.W). Patients in the surgery group used 0.5% levofloxacin eye drops (Santen, Japan) four times daily for three days prior to surgery. Preoperative preparations included full pupil dilation and topical anesthesia with oxybuprocaine eye drops (Santen, Japan). During surgery, a 2.8 mm temporal corneal incision was made, and the phakic IOL ICL-V4c (STAAR Surgical AG, Nidau, Switzerland) was implanted after viscoelastic injection, where the crystalline lens is left in place. The lens haptics were positioned in the ciliary sulcus, and viscoelastic was aspirated. Nobody was performed routine YAG laser iridotomy or surgical iridotomy. The procedure concluded without complications, and Tobramycin-Dexamethasone Eye Ointment (Santen, Japan) was applied, followed by gauze dressing. Postoperatively, patients used 0.5% levofloxacin and tobramycin-dexamethasone eye drops for one week, and 0.1% sodium hyaluronate eye drops (Ursapharm, Germany) for four weeks, all administered four times daily.

Statistical analysis

Statistical analysis was conducted using SPSS 26.0 software (SPSS Inc., Chicago, Illinois, USA). All measurement data underwent normality testing with the Kolmogorov-Smirnov test, and were expressed as mean ± standard deviation (mean ± SD). Based on the normality test results, comparisons of differences between preoperative and various postoperative follow-up time points were performed using the paired samples t-test or Wilcoxon rank sum test; inter-group comparisons between the surgery group and the non-surgery group were analyzed using the independent samples t-test or Mann Whitney U test; univariate continuous changes were assessed using repeated measures analysis of variance (Re-ANOVA) or Friedman’s test. A statistical difference exists when P < 0.05. Spearman correlation analysis was employed to examine the correlation between variables.