Real-time Localization Of Surgical Incision In Cataract Phacoemulsification

Cataract phacoemulsification is the main surgical procedure for the treatment of cataracts.With the development of microsurgery,astigmatism has become an important factor affecting the visual quality after surgery.The effect of astigmatism on postoperative visual acuity should be minimized to improve surgical quality.Research shows that different incision can cause different degree of postoperative astigmatism,when incision in cataract surgery for the steepest corneal limbus meridian direction,can effectively reduce postoperative corneal astigmatism,raise the level of patients with postoperative vision.Before cataract surgery,the corneal curvature maximum meridian is determined by corneal topography or corneal curvature,and a standard eye image is taken to plan the position of the incision.However,when making a corneal incision under a microscope,the surgeon needs to determine the position of the incision with the information of the preoperative standard image,and the intraoperative image has a certain scaling and rotation transformation compared to the preoperative standard image,resulting in the planned incision position Changes,the accuracy of the location mainly depends on the surgeon's clinical experience.Currently,there is a lack of clinical methods to accurately and timely provide incision site information for guiding a doctor to make a corneal incision.This subject uses image processing technology to quickly calculate the intraoperative incision position and display it,assisting the surgeon to quickly locate the incision for corneal incision.Since the limbus is located at the junction of the iris and the sclera,we use the method of locating the outer boundary of the iris to determine the limbus;the steepest meridian direction in the intraoperative image is determined by detecting the angle of rotation of the eyeball in the eye image in real time and combining the steepest meridian direction in the standard image;since the starting point of this topic is to solve the clinical application problems,a cataract surgical incision software was developed,the software integrates an algorithm that locates the limbus and an algorithm that locates the direction of the steepest meridian to calculate the position of the incision in the procedure and display it.The content of the paper is as follows:(1)Real-time localization of the limbus.In this paper,the edge of the cornea is located in real-time by real-time positioning of the outer boundary of the iris based on the outline-based minimal encirclement.In this method,the eye image is converted from RGB color space to HSV color space,the V-channel image is selected for subsequent processing,and median noise is used to remove the noise in the eye image;the grayscale characteristics of the eye image are analyzed,on the basis of this,a threshold segmentation method is used to process the V-channel image to obtain a binary image;the outline of the binary image is extracted,and the contour of the non-iris contour is cleared in conjunction with the size information of the iris;the outer boundary of the iris is located by calculating the minimum bounding circle of the iris contour to achieve the positioning of the cornea edge.(2)Real-time positioning of the steepest meridian.In this paper,the steepest meridian direction in the intraoperative eye image is located in real-time based on the real-time measurement of eyeball rotation angle and the steepest meridian direction before surgery.In this method,firstly,the sclera region adjacent to the iris in the eye image is selected as a recognition region;through the feature extraction and matching of the recognition region,a stable feature point pair is obtained;through the feature extraction and matching of the recognition area,in order to obtain a stable feature point pair;by calculating the rotation angle of the feature point with respect to the pupil center,the rotation angle of the eyeball in the image is obtained;in combination with the steepest meridional direction before the operation,the steepest meridian direction in the intraoperative eye image is calculated.(3)Development of cataract surgical incision positioning software.Based on the.Net Framework,EmguCV developed the cataract surgical incision positioning software system.The software integrates the real-time positioning of the limbus and the steepest meridian direction,and digitizes the incision information during cataract surgery to assist the doctor in quickly positioning the incision for corneal incision.In this study,the outer edge of the iris is located using the minimum bounding circle for calculating the contour to achieve the positioning of the limbus.In the video image test,the algorithm accurately locates the limbus with an average time of about 30 ms,which satisfies the real-time performance.By measuring the angle of rotation of the eye and combining the steepest meridian direction before surgery,the direction of the most steep meridian in the operation is obtained.This method can accurately calculate the direction of the steepest meridian in the operation,and the average time for processing an image is about 65 ms,Meet real-time requirements.The image processing software has a friendly operation interface,and the user can easily obtain the surgical incision position.This subject adopts image processing technology to locate the incision in real-time in cataract surgery,realizing the digital display of surgical incision information,and assisting doctors in quickly positioning the incision for corneal incision,which has potential clinical application value.