Ablation of Vitreous Tissue with a High Repetition Rate Erbium: YAG Laser

Abstract

Purpose

To quantify erbium (Er):YAG laser ablation of vitreous in relation to different pulse repetition rates ≤ 200 Hz, in order to examine the feasibility of laser for removal of vitreous gel (photovitrectomy) in clinically acceptable times.

Methods

Fresh porcine vitreous samples and saline controls were ablated in air with an Er:YAG laser connected to a sapphire fiber at pulse energies between 1.0 and 21.2 mJ and at pulse repetition rates between 10 and 200 Hz. Net ablation rates were determined by weight measurement.

Results

Reproducible and constant ablation rates were found for given laser parameters. Net ablation rates increased linearly with pulse repetition rate and nonlinearly with pulse energy. Expanded laser parameter domains permitted vitreous ablation rates as low as 1 μg/s to as high as 1031 μg/s. Ablation rates did not differ significantly between vitreous and saline.

Conclusions

The study documents clinically useful vitreous ablation rates that scale linearly with high repetition rates of Er:YAG laser, and suggests directions for further development of laser technology for enhanced removal of vitreous and other tissues. However, nonlinear effects of pulse energy also exist, indicating need for careful examination of ablation characteristics in various instruments.