Investigations for the Treatment of Presbyopia With Femtosecond Laser Pulses

Abstract

Abstract: : Purpose: According to Helmholtz’ theory of accommodation one of the mayor reasons for the development of presbyopia is the increasing sclerosis of the lens. One concept to delay the process of sclerosis or even regain the elasticity of the lens material is the treatment of the lens by femtosecond laser pulses. Methods: Our aim was to evaluate appropriate laser parameters for this possible treatment and to analyse potential elasticity changes of the treated lenses. We performed different cutting patterns in enucleated porcine lenses (ex vivo) and in rabbit lenses (in vivo). The laser pulses had a repetition rate of 5 kHz and a pulse duration of 120 fs. The pulse energies and spot separation of the laser pulses were varied to investigate the effect on the generated cut. For an evaluation of the gain in elasticity the lenses were rotated before and after treatment and the changes in the lens’ thickness was measured. Results: The effect of the generated cut was first of all classified by light scattering of the residual gas bubbles. The cuts with the smallest amount of light scattering could be generated with pulse energies of 680 nJ and a spot separation of 5 µm. With these parameters a smooth cutting was possible in porcine eyes. In the in vivo investigations no cataract generation was observable in the rabbit eyes. The rotation experiments showed an increase of elasticity in 70% of the eyes. As an average, the elasticity could be increased of nearly 20%, determined by the change of thickness between untreated and treated lens. Conclusions: Fs laser pulses seem to be capable for generation of cuts in crystalline lens material without harmful side effects as our preliminary in vivo studies showed.Further investigations on human presbyopic lenses (ex vivo) have to be performed to evaluate a possible change in accommodation.

Keywords: laser • refractive surgery: other technologies • aging: visual performance