Analysis of the effect of blue laser radiation on the structure of the auditory ossicles and audiological results of stapedoplasty

Background. Studies show that from 0.1 to 1% of the population suffers from otosclerosis, manifested by hearing loss and ear noise. Surgical treatment is performed using stapedoplasty, but there is always a risk of sensorineural hearing loss, dizziness and facial nerve paralysis. The laser method of stapedoplasty can reduce the risks, but it is also associated with potential negative consequences. Our study is aimed at analyzing the histological changes in the auditory ossicles after exposure to a diode blue laser with a wavelength of 445 nm.

Aim. To evaluate microstructural (histological) changes in the auditory bones (in particular the base of the stirrup) during stapedoplasty using a diode blue laser; to analyze the size of perforations in bone tissue and identify the effects of thermal effects on neighboring intact structures.

Materials and methods. To histologically assess the safety of using a diode laser with a wavelength of 445 nm, an experimental study was conducted on frozen human auditory bones. Laser exposure was performed on different areas of the bones with different parameters of power and exposure time, selected on the basis of previous studies. After exposure, the samples were fixed in a formalin solution and sent for histological analysis.

Results. The effect of thermal exposure, represented by areas of necrosis surrounded by perforated holes, showed values from 487 to 727 µm, with an average value of 608.6±91.5 µm. These data emphasize the focused nature of thermal exposure, while the preserved areas around bone defects did not reveal morphological differences with stirrup bones in the control group.

Conclusion. Microstructural measurements provided important information about the size of perforations and thermal effects, and histological analysis of the auditory ossicles confirmed their relative resistance to laser exposure, and thus the safety of exposure to the structures of the middle and inner ear. These results will be useful for further improvement of laser stapedoplasty techniques and increase its safety.