Safety and efficacy of corneal stromal lenticule implantation combined with corneal collagen cross-linking in the treatment of thinner keratoconus

Objective  To evaluate the safety and efficacy of stromal lenticule implantation addition keratoplasty combined with corneal collagen cross-linking (SLAK-CXL) in treating thinner keratoconus.

Methods  An observational case series study was conducted. Sixteen patients (16 eyes) with keratoconus who underwent SLAK-CXL at the Optometry Center of Ningxia Eye Hospital between February 2022 and June 2024 were enrolled. The patients’ best corrected visual acuity (BCVA), spherical equivalent (SE), corneal morphological parameters obtained by Pentacam three-dimensional anterior segment analyzer, and corneal biomechanical indicators obtained by Corvis ST biomechanical analyzer were recorded before surgery and 20 days, 3 months, 6 months, and 12 months after surgery. The occurrence of postoperative complications was observed. This study followed the Declaration of Helsinki. The study protocol was approved by the Ethics Committee of the People’s Hospital of Ningxia Hui Autonomous Region (No. 2022-NZR-035). All patients or their guardians were aware of the study purpose and signed the informed consent form.

Results  The BCVA before the operation, as well as at 20 days, 3 months, 6 months, and 12 months after the operation were 0.52(0.43, 0.79), 0.56(0.43, 0.79), 0.60(0.52, 0.68), 0.56(0.33, 1.23), and 0.52(0.30, 0.68), respectively, and the SE values were (-11.01±6.61), (-14.65±6.51), (-14.83±6.39), (-15.87±4.28), and (-15.88±5.05)D, respectively, with no statistically significant overall differences ( χ ²=5.044, F=3.660, both P>0.05). Among the corneal morphological parameters, the curvature of the flat axis of the anterior corneal surface increased at each time point following the operation compared to pre-operative measurements, while the curvature of the steep axis of the posterior corneal surface decreased relative to pre-operative values, but the curvature of the steep axis of the anterior corneal surface increased at 3, 6, and 12 months post-operation compared to pre-operative measurements, and the curvature of the flat axis of the posterior corneal surface decreased at 3 months post-operation compared to pre-operative values, showing statistically significant differences (all P<0.05). The thickness of the corneal apex and the thinnest point at each postoperative time point significantly increased compared to preoperative measurements, while the vertical asymmetry index exhibited a notable decrease compared to preoperative values (all P<0.05). The anterior surface height of the thinnest point at 20 days, 3 months, and 6 months postoperatively were significantly lower than that before the operation, the posterior surface height of the thinnest point at 20 days, 6 months, and 12 months after the operation were significantly reduced compared to preoperative values, the posterior surface height of the corneal apex at 3 and 6 months postoperatively were significantly lower than that before the operation, and the height-axis eccentricity index at 6 months postoperatively was reduced compared to baseline measurements, showing statistically significant differences (all P<0.05). Among the corneal biomechanical parameters, the topographic map combined with the biomechanical index and deformation amplitude ratio at 2 mm at 3 months postoperatively were lower than before the operation. The comprehensive deviation value of Belin/Ambrosio and the comprehensive radius index at 6 and 12 months postoperatively were lower than the preoperative values (all P<0.05). The ratio of the thinnest point to the rate of change of corneal thickness in the horizontal direction at 6 and 12 months postoperatively were higher than before the operation, and stiffness parameter applanation 1 levels at 20 days, 6 months, and 12 months after surgery were increased compared to baseline measurements (all P<0.05). At 6 months postoperatively, the reverse curvature radius of the maximum indentation increased compared to preoperative values, and the peak distance of the maximum indentation at 20 days postoperatively was reduced compared to baseline (both P<0.05). Throughout the follow-up period, no immune rejection, graft dissolution, wrinkling, or displacement of corneal stromal grafts were noted, nor was there any corneal opacity.

Conclusions  SLAK-CXL significantly increases the corneal thickness in thinner keratoconus eyes, enhances corneal rigidity, and improves corneal morphology. No significant adverse reactions were observed during the 12-month follow-up, indicating that the procedure demonstrates both safety and efficacy.