Abstract
PurposeTo investigate the effects of lenticule creation and subsequent corneal lenticule extraction on corneal deformation parameters during small incision lenticule extraction (SMILE) procedure.Materials and MethodsIn this prospective study, 18 eyes of 10 patients (27.90±7.11 years, −5.64±2.45 diopters) scheduled for SMILE procedure were enrolled. Changes in the corneal deformation parameters, including deformation amplitude (DA), applanation time(AT1 and AT2), applanation length(AL1 and AL2), corneal velocity(CV1 and CV2), peak distance(P.Dist.), radius and intraocular pressure values were measured preoperatively, immediately after lenticule creation and subsequent to corneal lenticule extraction in all eyes with the Corvis Scheimpflug Technology (Corvis ST, OCULUS, Wetzlar, Germany). Repeated measures analysis of variance (ANOVA) with bonferroni-adjusted post hoc comparisons was performed to investigate changes following each step of the procedure.ResultsAll surgical procedures were uneventful. A significant difference was detected among the three time points (pre-operation, post-lenticule creation and post lenticule extraction) for AT1 (P<0.001), AT2 (P = 0.001), DA(P<0.001), and IOP(P = 0.002). Bonferroni-adjusted post hoc comparisons indicated that there was no significant change in AT1, AT2, DA, or IOP after lenticule creation (post hoc P>0.05), but there was a significant change in these parameters following subsequent corneal lenticule extraction (post hoc P<0.01), when compared to values obtained pre-operatively. The scheimpflug camera of the Corvis ST demonstrated the intralamellar small gas bubbles formed from the vaporisation of tissue after lenticule creation and a gray zone was observed between the cap and the residual stromal bed after lenticule extraction.ConclusionsThere is a significant change in corneal deformation parameters following SMILE procedure. The changes may be caused predominantly by stromal lenticule extraction, while lenticule creation with femtosecond laser may not have an obvious effect on corneal deformation properties.
Highlights
Femtosecond laser has found an increasingly wide utilization in refractive surgeries including femtosecond laserassisted laser in situ keratomileusis (FS-LASIK) [1], femtosecond lenticule extraction (FLEx) [2] and small incision lenticule extraction (SMILE) [3] procedures
Bonferroni-adjusted post hoc comparisons indicated that there was no significant change in AT1, AT2, deformation amplitude (DA), or intraocular pressure (IOP) after lenticule creation, but there was a significant change in these parameters following subsequent corneal lenticule extraction, when compared to values obtained pre-operatively
The scheimpflug camera of the Corvis ST demonstrated the intralamellar small gas bubbles formed from the vaporisation of tissue after lenticule creation and a gray zone was observed between the cap and the residual stromal bed after lenticule extraction
Summary
Femtosecond laser has found an increasingly wide utilization in refractive surgeries including femtosecond laserassisted laser in situ keratomileusis (FS-LASIK) [1], femtosecond lenticule extraction (FLEx) [2] and small incision lenticule extraction (SMILE) [3] procedures. Uzbek [4] investigated the changes in biomechanical properties after flap creation using femtosecond laser and subsequent excimer laser ablation with an ocular response analyzer (ORA). He found a significant decrease in Peak 1 after both flap creation and after ablation. Significant reductions of corneal hysteresis (CH) and corneal resistance factor (CRF) were only detected after excimer laser ablation. He proposed that the major biomechanical consequence of intra-LASIK is in the ablation, while flap creation made a contribution to corneal biomechanical compromise
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