Corneal densitometry changes after SMILE Xtra versus SMILE for moderate to high myopia
- 1Shandong University of Traditional Chinese Medicine, Jinan 250014, Shandong Province, China
- 2Affiliated Eye Hospital of Shandong University of Traditional Chinese Medicine, Jinan 250002, Shandong Province, China
- 3Shandong Academy of Eye Disease Prevention and Therapy, Shandong Provincial Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Therapy of Ocular Diseases, Jinan 250002, Shandong Province, China
Abstract
AIM: To investigate the changes in corneal densitometry (CD) after small incision lenticule extraction combined with accelerated corneal cross-linking (SMILE Xtra) for correcting moderate to high myopia and to analyze their correlation. METHODS: In this non-randomized retrospective comparative study, participants who underwent surgery were enrolled in the standalone SMILE group and SMILE Xtra group, respectively. Preoperative and postoperative uncorrected visual acuity, spherical equivalent (SE), and CD values were recorded at 1, 3, 6, and 12mo. Measurements were taken in the central (0–2 mm), paracentral (2–6 mm), and peripheral (6–10 mm) zones, as well as in the anterior 120 μm, central, and posterior 60 μm layers of the cornea. A generalized linear mixed model (GLMM) was used to compare CD values between groups and at different time points, and the correlation between postoperative CD values and residual bed thickness (RBT) was analyzed. RESULTS: Totally 31 participants (62 eyes, mean age 20.32±2.76y) were in the standalone SMILE group and 28 participants (53 eyes, mean age 20.45±2.08y) in SMILE Xtra group. At 12mo postoperatively, there were no statistically significant differences in uncorrected visual acuity or SE between the two groups (P>0.05). Preoperative CD values in all regions showed no significant differences between groups (all P>0.05). In the central (0–2 mm) and paracentral (2–6 mm) zones, and the anterior, central, and total stromal layers, group, time, and interaction effects were all significant (all P<0.001). At 1, 3, and 6mo postoperatively, CD values in the SMILE Xtra group were significantly higher than those in the SMILE group within the 0–2 mm and 2–6 mm diameter ranges, as well as in the anterior, central, and total layers (all P<0.05). At 12mo postoperatively, CD values in the anterior layer remained significantly higher in the SMILE Xtra group compared to the SMILE group (P=0.007), whereas no statistically significant differences were observed in other diameter ranges or stromal layers (all P>0.05). Correlation analysis revealed that at 12mo postoperatively, CD values in all regions of both groups showed a significant positive correlation with RBT (all P<0.05), except for the anterior layer in the SMILE group, which showed no significant correlation with RBT (r=0.114, P=0.380). CONCLUSION: SMILE Xtra induces transient early increase in CD, primarily in the anterior and central layers. Although values stabilize or decline by 12mo postoperatively, the clinical significance of these long-term patterns requires cautious interpretation, considering the potential influence of post-surgical structural changes. Further research is necessary to fully elucidate the underlying contributions to these densitometric changes.
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BibTeX
@article{tang2026corneal,
title = {{Corneal densitometry changes after SMILE Xtra versus SMILE for moderate to high myopia}},
author = {Yi-Fan Tang and Su-Qi Xian and Peng Ji and Xiao-Fan Wang and Li Li and Hong-Sheng Bi},
journal = {International Journal of Ophthalmology},
year = {2026},
month = nov,
doi = {10.18240/ijo.2026.11.11},
url = {https://doi.org/10.18240/ijo.2026.11.11},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - Corneal densitometry changes after SMILE Xtra versus SMILE for moderate to high myopia
AU - Yi-Fan Tang
AU - Su-Qi Xian
AU - Peng Ji
AU - Xiao-Fan Wang
AU - Li Li
AU - Hong-Sheng Bi
PY - 2026
DA - 2026/11/02
JO - International Journal of Ophthalmology
DO - 10.18240/ijo.2026.11.11
UR - https://doi.org/10.18240/ijo.2026.11.11
AB - AIM: To investigate the changes in corneal densitometry (CD) after small incision lenticule extraction combined with accelerated corneal cross-linking (SMILE Xtra) for correcting moderate to high myopia and to analyze their correlation. METHODS: In this non-randomized retrospective comparative study, participants who underwent surgery were enrolled in the standalone SMILE group and SMILE Xtra group, respectively. Preoperative and postoperative uncorrected visual acuity, spherical equivalent (SE), and CD values were recorded at 1, 3, 6, and 12mo. Measurements were taken in the central (0–2 mm), paracentral (2–6 mm), and peripheral (6–10 mm) zones, as well as in the anterior 120 μm, central, and posterior 60 μm layers of the cornea. A generalized linear mixed model (GLMM) was used to compare CD values between groups and at different time points, and the correlation between postoperative CD values and residual bed thickness (RBT) was analyzed. RESULTS: Totally 31 participants (62 eyes, mean age 20.32±2.76y) were in the standalone SMILE group and 28 participants (53 eyes, mean age 20.45±2.08y) in SMILE Xtra group. At 12mo postoperatively, there were no statistically significant differences in uncorrected visual acuity or SE between the two groups (P>0.05). Preoperative CD values in all regions showed no significant differences between groups (all P>0.05). In the central (0–2 mm) and paracentral (2–6 mm) zones, and the anterior, central, and total stromal layers, group, time, and interaction effects were all significant (all P<0.001). At 1, 3, and 6mo postoperatively, CD values in the SMILE Xtra group were significantly higher than those in the SMILE group within the 0–2 mm and 2–6 mm diameter ranges, as well as in the anterior, central, and total layers (all P<0.05). At 12mo postoperatively, CD values in the anterior layer remained significantly higher in the SMILE Xtra group compared to the SMILE group (P=0.007), whereas no statistically significant differences were observed in other diameter ranges or stromal layers (all P>0.05). Correlation analysis revealed that at 12mo postoperatively, CD values in all regions of both groups showed a significant positive correlation with RBT (all P<0.05), except for the anterior layer in the SMILE group, which showed no significant correlation with RBT (r=0.114, P=0.380). CONCLUSION: SMILE Xtra induces transient early increase in CD, primarily in the anterior and central layers. Although values stabilize or decline by 12mo postoperatively, the clinical significance of these long-term patterns requires cautious interpretation, considering the potential influence of post-surgical structural changes. Further research is necessary to fully elucidate the underlying contributions to these densitometric changes.
SN - 2222-3959
SN - 2227-4898
ER -