To assess the intraoperative complications during small-incision lenticule extraction (SMILE) for myopia and myopic astigmatism correction and evaluate visual outcomes 6 months postoperatively. Tianjin Eye Hospital, Tianjin, China. Retrospective case series. Patients who had small-incision lenticule extraction surgery were examined 1 day, 7 days, 1 month, 3 months, and 6 months postoperatively. Demographic characteristics, visual outcomes, and intraoperative complications were recorded. Moreover, the incidence and management of the complications and the potential factors were analyzed. Of the 3004 eyes (1511 patients), 134 (4.46%) had intraoperative complications, including suction loss (28 cases [0.93%]), incisional bleeding (28 cases [0.93%]), opaque bubble layer (22 cases [0.73%]), subconjunctival hemorrhage (20 cases [0.67%]), black areas (10 cases [0.33%]), unintended posterior plane dissection (10 cases [0.33%]), tearing of the lenticule (8 cases [0.27%]), abrasion at the incision (5 cases [0.17%]), and inaccurate laser pulse placement due to eye movement (3 cases [0.10%]). The complications were resolved instantaneously using appropriate management procedures; all cases had good visual outcomes. Six months postoperatively, 99.80% of cases had an uncorrected distance visual acuity better than 20/25 and the mean corrected distance visual acuity was -0.06 logarithm of the minimum angle of resolution ± 0.07 (SD). Although small-incision lenticule extraction shows promising outcomes for correction of myopia and myopic astigmatism, intraoperative complications still inevitably occur. However, satisfactory visual outcomes may be achieved using appropriate management techniques.

Purpose: The purpose of this article was to evaluate intraocular pressure (IOP) changes and investigate the relationship with corneal biomechanics after small-incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). Methods: A total of 193 eyes of 193 patients who underwent SMILE and FS-LASIK procedures were included in this retrospective study. Data were collected preoperatively and postoperatively, including Goldmann-correlated IOP (IOPg), corneal-compensated IOP (IOPcc), corneal hysteresis (CH), and corneal resistance factor (CRF) by ocular response analyzer, noncontact intraocular pressure (IOP_NCT) by noncontact tonometer, and Ehlers, Shah, Dresden, Kohlhaas, Orssengo/Pye by the Pentacam corrected system. Changes in both groups and differences between groups were evaluated. Multiple linear regression models were constructed to explore factors influencing IOP changes. Results: In SMILE, the IOPg, IOPcc, IOP_NCT, and Kohlhaas decreased significantly at 1 month postoperatively (P < 0.01), whereas with the Ehlers formula they significantly increased (P < 0.01). IOPs decreased at 3 and 6 months compared with all preoperative values except Ehlers values (P < 0.01), but there was no significant difference between 3 and 6 months (P > 0.05). In FS-LASIK, the IOPg, IOPcc, and IOP_NCT decreased significantly at 1 month (P < 0.01), whereas in the Ehlers and Shah formulas they significantly increased (P < 0.01). Compared with preoperative values, the IOPs decreased at 3 and 6 months except in the Ehlers and Shah formulas (P < 0.01). Only IOPg and IOPcc differed between 3 and 6 months (P < 0.05). The Ehlers and Shah formulas were closer to the preoperative IOP for both groups, with variation approximately 1 mm Hg at 6 months postoperatively. Preoperative IOP, postoperative corneal resistance factor, corneal hysteresis, and flat keratometry were enrolled into the regression equations. Conclusions: IOP underestimation after SMILE or FS-LASIK was related to corneal biomechanics as well as preoperative IOP and flat keratometry. IOP after SMILE seem to remain more stable. Accordingly, the Ehlers and Shah formulas were closer to the preoperative IOP. It may be useful to estimate future IOP with the best-fit models after surgery.

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.

Purpose: To investigate real-time intraocular pressure (IOP) during small incision lenticule extraction (SMILE) in rabbit eyes for myopia correction. Methods: During SMILE, real-time IOP was measured in the vitreous cavity of rabbit eyes with an optic fiber pressure sensor (OFPS). Two groups (n = 6 for each) underwent surgery, one group for a −2.00 diopter (D) refractive spherical correction and the other for a −6.00 D correction. Results: During surgery, the IOP increased once the glass contact attached to the cornea (Pre-suction), and peaked 83.94 mmHg (SD ± 23.87 mmHg) for the −2.00 D group and 89.17 mmHg (SD ± 22.66 mmHg) for the −6.00 D group, both average values were less than 110 mmHg when suction was initiated to fix the glass contact onto the cornea (Suction on). It then fell to 74.81 mmHg (SD ± 20.64 mmHg) and 76.94 mmHg (SD ± 27.43 mmHg), respectively, and remained stable during lenticule creation (Cutting). After suction stopped (Suction off), IOP fell steeply. During lenticule separation/extraction, the change in IOP was 32.26 mmHg (SD ± 2.91 mmHg). Notably, the average duration of elevated IOP during the surgery was 166.05 s (no longer than 3 min). Conclusions: The IOP fluctuations in the vitreous cavity using an OFPS in a rabbit model during SMILE showed that real-time IOP significantly was increased during Pre-suction, Suction on, Cutting, Suction off, and lenticule separation/extraction compared to baseline IOP, although, peaked at Suction on. Neither the degree of myopic correction nor central corneal thickness significantly affected these changes in IOP.