Clinical outcomes of laser epithelial keratomileusis using a 213 nm wavelength solid-state laser
The 213 nm wavelength generated by solid state platforms (e.g., Pulzar Z1, CustomVis, Perth, Australia) demonstrates superior transmissibility through water compared to 193 nm, so is less sensitive to levels of corneal hydration, and may reduce the variability in refractive outcomes linked with corneal hydration; corneas that become dehydrated during excimer laser treatment are often overcorrected, while superhydration is linked with undercorrection.3 Furthermore, the absence of dangerous gas eliminates sudden noise, and patient anxiety, as laser operation commences, while maintenance costs are also substantially reduced.
Earlier this year, we reported outcomes from a cohort of patients undergoing laser epithelial keratomileusis (LASEK) performed by the same surgeon using the CustomVis solid-state refractive laser.8 The CustomVis system generates a 213 nm wavelength by transmission of a 1064 nm Nd:YAG laser beam through three non-linear crystals. The 0.6 mm diameter quasi-Gaussian-shaped flying spot has a 300 Hz pulse repetition rate, and the system employs three methods of eye tracking technology: a limbus-based eye tracker with a closed-loop response of 1-kHz, a video eye tracker to facilitate a higher level of accuracy and a video gaze tracker, confirming patient fixation.
The cohort included 245 eyes of 134 patients with a mean age of 41.0 ± 12.2 years. Patients had a broad range of preoperative refractive errors, with sphere values ranging from –9.50 to +6.50 D (mean –1.59 ± 3.22 D) and astigmatism between 0 and –5.50 D (mean –0.98 ± 1.17 D). Postoperative follow-up visits were scheduled at 2 and 6 months.
LASEK surgery performed on this substantial cohort was shown to be effective, safe and stable over the follow-up period. Over 95% of eyes maintained the same best corrected distance visual acuity (CDVA) postoperatively, or gained a line, and the mean postoperative spherical equivalent refractive error (SE) was stable between the 2 month (–0.01 ± 0.57 D) and 6 month (–0.01 ± 0.55 D) visits. Treatment was accurate for both myopes and hyperopes, with mean SEs at 6 months of +0.02 ± 0.27 D and 0.21 ± 0.66 D, respectively.