Changes in Corneal Volume at Different Areas and Its Correlation with Corneal Biomechanics after SMILE and FS-LASIK Surgery

Pinghui Wei; George Pm Cheng; Jiamei Zhang; Alex Lk Ng; Tommy Cy Chan; Vishal Jhanji; Yan Wang

doi:10.1155/2020/1713979

Changes in Corneal Volume at Different Areas and Its Correlation with Corneal Biomechanics after SMILE and FS-LASIK Surgery

J Ophthalmol. 2020 Apr 27:2020:1713979. doi: 10.1155/2020/1713979. eCollection 2020.

Authors

Pinghui Wei^{1

2}, George Pm Cheng³, Jiamei Zhang^{1

2}, Alex Lk Ng⁴, Tommy Cy Chan⁵, Vishal Jhanji⁶, Yan Wang^{1

2}

Affiliations

¹ Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China.
² Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin Key Lab of Ophthalmology and Visual Science, Nankai University, Tianjin, China.
³ Hong Kong Laser Eye Center, Hong Kong, China.
⁴ Department of Ophthalmology, The University of Hong Kong, Hong Kong, China.
⁵ Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China.
⁶ UPMC Eye Center, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.

Abstract

Purpose: To investigate the variations of corneal volume (CV) after small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) and analyze the influences of biomechanical properties on the changes of refraction and CV.

Methods: Ninety-seven eyes of 97 patients undergoing SMILE and FS-LASIK were included in this retrospective study. CV was measured with Scheimpflug-based corneal topography at preoperatively and at day 1, week 1, and months 1 and 3 postoperatively. CV measured within 5 mm diameter was defined as central region volume (CV5) and between 5 mm and 10 mm diameter was defined as peripheral region volume (CV5-10). An Ocular Response Analyzer (ORA) was used to assess corneal biomechanical properties including corneal hysteresis (CH) and corneal resistant factor (CRF). The reduction of study parameters (△) were calculated by subtracting the preoperative value at various time points from the postoperative values.

Results: CV had significant reduction after the SMILE and FS-LASIK procedure (P < 0.05). CV5 increased significantly from postoperative day 1 to month 3 (P < 0.001) in SMILE, while both CV5 and CV5-10 increased significantly in FS-LASIK (P < 0.001). The increase in CV5 after SMILE was 0.11 ± 0.16 mm³，which was significantly different from FS-LASIK (0.20 ± 0.13 mm³, P=0.004). In the SMILE group, △CV5 correlated with △CRF (r = 0.498, P < 0.001) and △CH (r = 0.374, P=0.007). In the FS-LASIK group, △CV5 and △CRF had a significant correlation (r = 0.363, P=0.012), but not with △CH.

Conclusions: Dynamic changes in corneal volume were found after SMILE and FS-LASIK surgery. The central region significantly increased after SMILE, while both central and peripheral regions increased following FS-LASIK in the early postoperative period. SMILE was associated with less change in biomechanical properties per unit of reduction in CV compared with FS-LASIK.