Ex-vivo study on the surface quality of corneal lenticule and stroma after low energy femtosecond laser lenticule extraction

Abstract

This study aimed to assess the surface quality of cap, stroma and lenticular surfaces created using low-energy femtosecond laser lenticule extraction (Ziemer FEMTO LDV Z8). Twenty-four porcine eyes were divided into four groups (n = 6 each): two with optimal laser power (32%) with posterior curvature equivalent to a spherical correction of -2D and -5D, respectively and the other two with high power (64%) with spherical correction of -2D and -5D respectively. Samples were analysed using scanning electron microscopy (SEM). Surface morphology was evaluated using a standard scoring system; surface relief, surface regularity, extent and position of irregularities were graded by four independent clinicians. Eyes with 32% power and -2D correction had significantly less size of the irregular area than those with -5D; however, no significant difference was found between the two groups with 64% power. When comparing eyes with -2D correction, the size of the irregular area was lesser with 32% power. Surface relief was lesser with -5D correction with 32% power than 64% power. Low-energy femtosecond laser lenticule extraction (Ziemer FEMTO LDV Z8) produces good surface quality results. There is a tendency for smoother surface stromal quality with lower power settings than a higher power.

Evaluation of Higher-Order Aberrations After the Smooth Incision Lenticular Keratomileusis (SILKTM) Procedure Using the ELITATM Femtosecond Platform for Correction of Myopic and Astigmatic Refractive Errors

“… 40 A recent study has also shown that the Clear procedure with Ziemer FEMTO LDV Z8, using lower FS energy and overlapping spot density, produced smoother lenticule surfaces for corneal lenticule extraction. 41 Literature on SMILE procedures 42–44 has indicated that patients treated with the VisuMax500 using lower energy settings and smaller spot spacing (laser energy of 125–135 nJ; spot spacing of 4.5 μm) achieved significantly smoother separations, faster visual recovery, and improved visual outcomes.…”

Assessment of Changes in Cap and Residual Stromal Thickness Values during a 6-Month Observation after Refractive Lenticule Extraction Small Incision Lenticule Extraction

“…The procedure is a controversial topic with respect to children and youths under the age of 18, but it is possible in the case of children with high anisometropia and the risk of amblyopia [13,14]. Research has shown that the ReLEx SMILE procedure is similar to LASIK in terms of the effectiveness, safety, predictability, and stability of its results [15][16][17][18].…”

Incisional surface quality of electron-beam irradiated cornea-extracted lenticule for stromal keratophakia: high nJ-energy vs. low nJ-energy femtosecond laser

“…The first commercially available femtosecond laser system capable of this was the VisuMax developed by Carl Zeiss Meditec (Jena, Germany), which trademarked their ReLEx procedure as Small Incision Lenticule Extraction (SMILE) (3,4). More recently Ziemer Ophthalmic Systems (Port, Switzerland), who developed the FEMTO LDV, introduced a similar procedure referred to as cornea Lenticule Extraction for Advanced Refractive-Correction (CLEAR) (5,6). Although the lasers have different technical specifications and employ different photodisruptive processes-VisuMax employs high nano Joule (nJ)-energy and low-frequency pulses, while FEMTO LDV employs low nJ-energy and highfrequency pulses (Table 1), both lenticule extraction procedures involve precise laser firings that photo-disrupt the stromal material creating a posterior and then anterior lenticular surface.…”