Hollow waveguide delivery system for the ophthalmology treatment

Abstract

For the purpose of the ophthalmology treatments a special hollow waveguide based delivery instrument was developed. It consists of a 2 m long cyclic olefin polymer coated silver hollow glass waveguide (inner diameter 700 μm) and the special cap allowing the contact of the waveguide with the wet eye tissues. The transmission characteristics for a delivery of a mid-infrared Er:YAG radiation (2.94 μm) was measured. Then the pre-clinical interaction experiments of the Er:YAG laser radiation with the eye tissue (cornea, lens, and sclera) were performed with this delivery instrument. A comparison of two types of interactions results - the action of Er:YAG free running - 40 μs long pulses and giant 450 ns long pulses were made. The human eye tissues (in vitro) were cut and samples (cornea, lens, and sclera) were gradually irradiated by the mid-infrared radiation with the energy of 7 mJ (the corresponding spot size diameter was equal ~ 700 μm). The laser energy density used in this experiment was 1.8 J/cm². From results it can be concluded that the giant pulses are more efficient in the ablation of the cornea, they are comparable with the free-running long pulses in the case of lens grinding, and they are less functioning for the sclera perforation. As concern the hollow waveguide delivery system, it has been proved that the energy delivered by this system was sufficient and suitable in both cases for delivery of long - free-running pulses, and short - giant pulses as well.