Research On Key Technology Of Surgery Navigation System For Femtosecond-laser Assisted Cataract

The combination of femtosecond-laser technology and anterior segment optical coherence tomography provides a complete "no-knife" automated surgical solution for cataract surgery,which has an unparalleled advantage compared with manual surgery.Femtosecond laser assisted cataract surgery is the future direction for cataract treatment.Its core technology is to realize the accurate facula navigation process.Facing the current situation of foreign monopoly on this technology,in this paper,we studied the key technologies of the navigation system and achieved the two key technologies,including the three-dimensional(3D)reconstruction of eye tissue and the solution of facula trajectory during surgical navigation.The reconstructed ocular tissues can be used for eye disease diagnosis,preoperative planning.Combined with the facula trajectory generation algorithm,the ocular tissue triangle model can be used to guide the surgery process.The main contents of this paper are as follows:First of all,this paper analyzed the key technology of femtosecond laser-assisted cataract surgery navigation system.Based on the characteristics of the cataract surgery's procedure,an eyeball fixation device was introduced.This device is fixed to the eyeball by suction ring to achieve the eye and laser scanning system coordinate system unified.And then,combined the MATLAB,VTK,OpenGL with VS2010 MFC single document program to build a navigation software system through the Cmake programming cross-platform.Secondly,since the optical coherence tomography(OCT)is a key module in femtosecond laser-assisted cataract surgery system,which is an important basis for cataract preoperative diagnosis,surgical planning and navigation.In this paper,the image sequence which obtained by the Visante anterior segment OCT device is preprocessed by median filtering,threshold segmentation and edge detection.Then the spatial position registration of the image sequence is performed based on the image feature points.This part of the work explored the OCT image processing methods and then prepared for the 3D reconstruction of eye tissue.On the basis of the above,an improved ray casting method for rendering radial anterior segment optical coherence tomography images was proposed,which provided the intuitive 3D reconstruction information for the diagnosis of cataract.Meanwhile,the sparse data field of the extracted ocular tissue was interpolated by cubic B-spline interpolation.The cornea and lens were reconstructed by planar contours and then stored in STL triangular format,which can be used to solve the facula trajectory.Finally,according to the necessary of femtosecond laser assisted cataract surgery incision,the surgical incision track was planned.An algorithm for solving the trajectory of the cataract surgery for cataract surgery was proposed.The mathematical model of the trajectory is established and then simulated in MATLAB.And visualization experiments was carried out by surgical navigation visualization software platform,more intuitive eye tissue model and surgical incision program were displayed,which can interactively achieved multi-angle observation.And then the facula trajectory was verified by the femtosecond laser experiment platform,which lays the foundation for femtosecond laser cataract surgery navigation.