No abstract

Rapid UV cross-linking treatment can be regarded as equivalent to the standard procedure in terms of increase in corneal stiffness. The new rapid protocol shortens the treatment duration by more than two thirds, from 30 to 9 minutes. The safety of the higher intensities must be addressed in further clinical studies.

This theoretical model predicts the spatial distribution of increased stiffness by corneal cross-linking and, as such, can be used to customize treatment, according to the patient's corneal thickness and medical indication.

Generating particular cutting patterns inside lens tissue can increase the deformation-ability of the crystalline lens. Thus, it might be one possible way to treat presbyopia.

The intended depth of CXL using current light sources is achieved only within the central area of the cornea. To provide CXL to the peripheral cornea, the ultraviolet beam either should have an improved intensity profile or may have to be decentered.

The creation of gliding planes with a fs laser inside the crystalline lens tissue can change the deformation ability of the lens. This might be an indication for a possible method to treat presbyopia in future.

We present a high-speed photographic analysis of the interaction of cavitation bubbles generated in two spatially separated regions by femtosecond laser-induced optical breakdown in water. Depending on the relative energies of the femtosecond laser pulses and their spatial separation, different kinds of interactions, such as a flattening and deformation of the bubbles, asymmetric water flows, and jet formation were observed. The results presented have a strong impact on understanding and optimizing the cutting effect of modern femtosecond lasers with high repetition rates (>1 MHz).

Nowadays UV-cross-linking is an established method for the treatment of keraectasia. Currently a standardized protocol is used for the cross-linking treatment. We will now present a theoretical model which predicts the number of induced crosslinks in the corneal tissue, in dependence of the Riboflavin concentration, the radiation intensity, the pre-treatment time and the treatment time. The model is developed by merging the difussion equation, the equation for the light distribution in dependence on the absorbers in the tissue and a rate equation for the polymerization process. A higher concentration of Riboflavin solution as well as a higher irradiation intensity will increase the number of induced crosslinks. However, performed stress-strain experiments which support the model showed that higher Riboflavin concentrations (> 0.125%) do not result in a further increase in stability of the corneal tissue. This is caused by the inhomogeneous distribution of induced crosslinks throughout the cornea due to the uneven absorption of the UV-light. The new model offers the possibility to optimize the treatment individually for every patient depending on their corneal thickness in terms of efficiency, saftey and treatment time.