Nanojoule laser reduces eye damage

17 Jun 2002

Researchers in Germany say using low-energy pulses will make laser eye surgery safer.

From Opto & Laser Europe magazine

Using nanojoule femtosecond pulses could reduce collateral damage to eye tissue during laser surgery, according to a study by a team based in Jena, Germany.

In comparison with the femtosecond laser procedures performed on eye tissue to date, which have employed microjoule pulses, the lower-energy source appears to generate smaller cavitation bubbles, and therefore less potential damage (Optics Express 10 171).

Femtosecond laser-based refractive eye surgery looks set to gain significant market share as concerns regarding the LASIK procedure grow (see related story).

Karsten König and colleagues based at Jenlab, a spin-off of the laser microscopy division of Jena University, used an unamplified Ti:sapphire source (Coherent's Vitesse laser) emitting 170 fs pulses at 800 nm. Rather than amplifying the pulse energy to overcome the optical breakdown threshold, as is normally the case, the laser was focused to its diffraction limit using a 1.3 numerical aperture lens.

In their animal studies, the team used beams with an average power of 80 mW to ablate ocular tissue. It was then possible to image the effects of this ablation using the same set-up, but reducing the average power to 5-10 mW. The laser system was previously used by the Jenlab team to dissect DNA samples.

Unlike microjoule pulses, says König, the lower energy reduces the potentially damaging effects of the bubbles that form during the process. Bubbles as large as 12 µm have been predicted to form using the microjoule source, but König's mean measurement of bubble diameter using the Jena team's technique was just 5 µm.

Along with its uses in intraocular surgery, the team predicts that the procedure could also improve neuronal surgery. The researchers now plan to examine the quality of the laser cuts by electron and force microscopy.

Author
Michael Hatcher is technology editor of Opto & Laser Europe magazine.