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Anterior Segment OCT Thickness Difference Maps for Monitoring Corneal Thickness Changes: Small-Incision Lenticule
Yi-Ting Hou1,2,3, Wei-Lun Huang3,4, Hsu-Hang Yeh1
1Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan.
Purpose:
To develop and validate a self-reconstructed anterior segment optical coherence tomography (AS-OCT) thickness difference map to precisely quantify corneal changes, using lenticule thickness in small-incision lenticule extraction (SMILE) as a model.
Methods:
This retrospective study included 22 patients (44 eyes) who underwent SMILE. Using a self-developed R software script, we reconstructed corneal and stromal thickness difference maps from 40,000-point raw AS-OCT data spanning a 10-mm central corneal diameter. The estimated lenticule thickness (ELT) was defined as the maximum thickness change and compared against planned lenticule thickness (PLT) from the VisuMax laser readout. We also compared ELTs derived from Pentacam Scheimpflug tomography at the thinnest and vertex points.
Results:
At 3 months postoperatively, the ELT retrieved form reconstructed corneal thickness difference map (CTDM) and stromal thickness difference map (STDM) from AS-OCT demonstrated smaller discrepancies with PLT (4.80 ± 9.85 µm and 1.53 ± 6.59 µm, respectively) compared to discrepancies between PLT and Pentacam thinnest point lenticule thickness (PTLT) and Pentacam vertex point lenticule thickness (PVLT) (14.21 ± 13.66 µm and 12.8 ± 13.88 µm) (both P < 0.001). STDM showed much stronger correlation with PLT (R2 = 0.88) than CTDM, PTLT, and PVLT (R2 = 0.87, 0.79, and 0.79, respectively) (analysis of variance, P = 0.039).
Conclusions:
The self-reconstructed AS-OCT thickness difference map accurately measures ELT after SMILE, outperforming Scheimpflug tomography in precision and reliable monitoring of corneal thickness changes.
Translational Relevance:
This technique enables accurate layer-specific corneal thickness monitoring, supporting safer surgical planning and enhanced assessment of postoperative or pathological corneal changes in clinical ophthalmology.
