Research On Key Technology In Measurement And Correction Of Human Eye's Wave-front Aberration

In recent years, with the development and improvement of the optical measurements, the techniques for wavefront aberration measurement and correction have been developing rapidly. At present, wavefront aberration guided customized corneal ablation surgery has become the researching focus in ophthalmology. The paper has studied the key techniques for the measurement of wavefront aberration of the human eye's, wavefront aberration correction surgery and excimer laser refractive surgery. Main research achievements of the paper are as following:1. The principle of human eye's visual optics was systematically described. The concept and classes of the human eye's wavefront aberration were presented. The mathematical expressions of the wavefront aberration based on Taylor series and Zernike polynomials were also presented.2. The key techiniques of image processing and auto-tracing in subjective wavefront aberrometer were systematically researched. Using Ostu method to segment the captured pupil's image, then applying Multiple detecting method for tacing the boundary of pupil's image. The coordinates of the pupil's center and the radii was calculated using Point Hough Transform under the principle of equal distance selecting points and large distance combining points. In order to compensate the movement of the eye in the process of measuring eye's wavefront aberration, the auto-tracing technique was used.3. The technique for wavefront reconstruction based on Zernike polynomials was researched. The fitting algorithm based on developed Gram-Schmidt orthogonalization and Householder transformation were put forward. The unknown Zernike coefficients could be wored out using these two fitting algorithm. The fitting precision of these two algorithms was also compared with traditional constructing normal equation group method.4. The key techniques for excimer laser refractive surgery were presented. The refractive correction model based on aspherical factor was put forward. The transition zone model was also bring forward. Ablation models based on aspherical factor were simulated on computer. The model could be used to correct the simple myopia and simple hyperopia. Using this model can effectively reduce the spherical aberration in postoperative eyes and decrease the regression of visual sights.5. The key techniques in wavefront-guided laser customized ablation surgery were developed. The ablation profile for the correction of wavefront aberration is presented and simulated on computer. The process of scanning-spot excimer laser was studied and simulated on computer.6. The hardware system and software system of subjective wavefront aberrometer was presented. The ablation model was used in ophthalmic excimer laser system (AOV-FB system). With the cooperaton of Suzhou 66 Vision Tech Co.Ltd, the subjective wavefront aberrometer has been developed. It can accurately measure the low-order and high order aberrations in humen eyes. Combined with AOV-FB, it makes the Ophthalmic excimer laser system (AOV-FB system). At present, the system has entered the industrialization period. It will be widely used in the future.