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 overcome this hardening of the lens is to regain its flexibility by inducing gliding planes inside the lens. Femtosecond laser pulses are a suitable tool for this treatment.
Methods::
Showing in former work that we could increase the flexibility of enucleated porcine (ex vivo) lenses up to 25 %, we focused our recent work on human autopsy lenses. The age of the human donors ranged between 30 and 70 years. We performed our work first with laser pulse with a repetition rate of 5 KHz and a pulse duration of 130 fs, later on we used a 100 KHz laser system with a pulse duration of 440 fs which reduced treatment time. For an evaluation of the gain in flexibility the lenses were rotated before and after treatment and the changes in the lens’ thickness were measured with Fisher’s spinning test. In addition we measured the thickness and diameter of the lenses before and after the treatment.
Results::
Depending on age and the applied cutting pattern the lens thickness increased up to 0,4 mm after the laser treatment leading to a theoretical increase of refractive power of several dioptres. The rotation experiments showed an increase of elasticity for all eyes. The flexibility could be increased in average about 70% compared to the measurements before treatment. Since the age of the human donors had a broad range, leading to different degrees of lens hardening, the variance of the measured flexibility changes was up to 30%.
Conclusions::
Fs-laser induced cuts in the lens lead to a gain in lens flexibility and an increase in thickness after the laser treatment. Therefore this might be a possible presbyopia treatment in phakic eyes. Further investigations which show a correspondence of gain in flexibility and change of accommodative power in vivo as well as wound healing studies have to be performed.
Keywords: presbyopia • laser