The effects of the Ziemer LDV Z8 low-energy, high-frequency liquid optic interface system during femtosecond laser lens capsulotomy and fragmentation

Abstract

Purpose: To determine the effects of the low-energy, high-frequency Ziemer LDV Z8 liquid interface femtosecond laser platform during capsulotomy and lens fragmentation.

Methods: Ex vivo cadaveric porcine eyes harvested at <6 post hours enucleation were evaluated with the Ziemer LDV Z8 femtosecond laser during fragmentation (8 segment, 5.3mm diameter, 0.8mm height, cut speed 50mm/s, energy 90%) for different capsulotomy sizes (4, 5 or 6mm diameter, 2.8mm height, cut speed 10mm/s, energy 100%). Lens capsules were removed for evaluation of edge by circularity (Image J) and scanning electron microscopy (SEM). Lens capsule strength was determined by the single column universal testing system (Instron).

Results: All procedures were completed successfully without complication. Of 18 eyes undergoing Femto-cataract with the Z8 laser, the total time to completion was 216 seconds (SD 43s). There was a significant difference in the time taken to complete surgery with increased capsulotomy sizes (p=0.01). The lens capsule circularity achieved was high at 0.98 with no demonstrable influence of size with larger capsulotomy (p=NS). Small removable tags were evident on SEM in 2/18 cases but otherwise smooth edges were observed. The capsule tension was measured at 79mN at 4mm and 139mN at 6mm (p<0.01)). When inducing corneal oedema by prolonged storage (>24 hours), the mean corneal thickness increased (766mm vs. 1035mm, p<0.001) and demonstrated a significantly higher rate of complications at a fixed laser energy setting including an increase in tags (2/6), one demonstrable capsule rip and significant decrease in circularity (0.9, p<0.05). No problems were encountered during fragmentation.

Conclusions: The Ziemer LDV Z8 utilises a precision optical laser through a liquid interface, delivering reduced energy with each pulse. We found that the platform created a reliable and circular capsulotomy but with increased resistance to tension with larger capsule sizes. Extreme corneal oedema induced by excessive storage showed a predictable and commensurate reduction in quality of capsulotomy, albeit at fixed energy. Further investigation to determine the effect of capsulotomy size on resistance to tension and the limits of corneal opacification for safe procedure are warranted in human eyes.