This is a single-blind, single-center, parallel-group randomized controlled trial with the following objectives: First, researchers aim to compare the clinical efficacy of 2mm and 2.5mm post-limbal needle insertion in YAMANE technique for patients with congenital ectopia lentis. Second, the goal is to investigate the mean absolute refractive prediction error, IOL tilt and decentration, uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), and corneal endothelial cell count at 3 months postoperatively. Third, it intends to explore the incidence of postoperative complications of the two needle insertion positions in this specific surgical method. Finally, this study aims to provide evidence for ophthalmic clinical practice, explore the optimal needle insertion point, and offer more precise and safe surgical plans for patients requiring sutureless transscleral IOL fixation.

For patients with insufficient capsular bag support caused by congenital developmental abnormalities, trauma, or other etiologies and who meet the indications for intraocular lens (IOL) implantation, IOL suspension surgery is the primary surgical procedure. As an innovative IOL suspension technique, the YAMANE technique has been widely favored by ophthalmologists. Due to its sutureless feature, this technique reduces the risk of postoperative complications such as infection and hypotony, while greatly simplifying surgical procedures.

In previous studies on the YAMANE technique, needle insertion sites were commonly set at 2 mm and 2.5 mm posterior to the cornea limbus. Among them, the 2.5 mm post-limbal insertion point was associated with a smaller mean absolute refractive prediction error and better clinical outcomes. Although a few studies have evaluated the clinical efficacy of the YAMANE technique, no study has systematically compared its clinical outcomes between different needle insertion positions. Considering that differences in the insertion point may directly affect postoperative refractive status, IOL stability, and visual outcomes, evaluating the impact of different insertion sites on surgical results is critical for optimizing surgical strategies and improving therapeutic efficacy.

In this randomized controlled trial, the investigators will systematically investigate the clinical efficacy of needle insertion at 2 mm versus 2.5 mm posterior to the cornea limbus in the YAMANE technique. Through this study, the investigators aim to provide evidence for ophthalmic clinical practice, explore the optimal needle insertion point, and offer a more precise and safe surgical plan for patients undergoing the YAMANE technique.

Inclusion Criteria:

1. Patients aged 4-18 years (regardless of gender) who meet the indications for YAMANE technique.
2. Patients who can complete a follow-up period of at least 3 months after surgery.
3. Patients or their legal guardians who provide informed consent to participate in this study.

Exclusion Criteria:

1. Patients with concurent secondary qlaucoma, retinal detachment, strabismus, or other relevant ocular complications (excluding refractive errors).
2. Patients participating in other trials that may affect the results of this study.

This study adopts a single-blind design, with no blinding of investigators but with blinding of participants and assessors implemented. To reduce bias under the single-blind condition, trial-related personnel involved in participant screening remain blinded, and clinical staff conducting routine ophthalmological examinations as well as data analysts are kept blinded to the treatment allocation.