Research On Customized Design Of Ortho-K Lens Based On Corneal Reconstruction

The number of myopia cases worldwide has been increasing year by year,and there is a trend of younger age groups being affected.Countries around the world attach great importance to the issue of myopia,and China has issued relevant policies to control the growth of myopia rates.Patients who wear ordinary frame glasses will deepen their myopia degree as the central parallel light focuses on the retina and the peripheral parallel light focuses on the back of the retina.High myopia will increase the possibility of pathological myopia in patients.Ortho-K lenses can effectively suppress myopia growth by flattening the central cornea.However,regular Ortho-K lenses require patients to try on many pairs,with a strong foreign body sensation,which is not easily accepted.The Ortho-K lenses in this article are customized based on the patient’s cornea,with better adaptability,less foreign body sensation,and better treatment effects.The research content of this article is as follows:Firstly,the collection method of corneal curvature data based on the Placido disc model was studied,and the corneal structure was reconstructed based on the curvature data.The missing curvature data were interpolated using methods such as local mean interpolation,nonlinear regression interpolation,and inverse distance weighting interpolation,and the inverse distance interpolation method with better interpolation effect was selected to interpolate the missing values.The Z-score method was used to detect outliers in local data,and based on the local data,the two-dimensional moving Gaussian weighted average filter was used to calculate the smoothed value to replace the detected outliers.The corneal structure was reconstructed using the processed corneal curvature data,and the corneal structure coordinate information was processed in the same dimension,and then the corneal structure data was expanded.Secondly,based on the corneal structure,the customized design method of Ortho-K lenses was studied.According to the design principle of Ortho-K lenses,a multi-curve design was adopted,including alignment curve,base curve,reverse curve,and peripheral curve.The alignment curve was designed to be parallel to the corresponding position of the cornea.The base curve was designed with a non-spherical surface using an improved spherical surface design formula to calculate the base curve curvature radius in each semiline direction.The reverse curve was modeled according to the tear film morphology and was reverse-engineered based on the corneal structure.The peripheral curve was designed with a linearly increasing tear film thickness based on the selected peripheral curve height.At the intersection of the main curves,there were two sharp points,which were smoothed by using a second-order Bezier curve.The reverse curve and the alignment curve connecting curve segment controlled the gradual change of the tear film curve and adopted a smooth transition design.The design of the Ortho-K lens was optimized by increasing the Jessen coefficient and reducing the base curve width.The segmented encoding was used to simulate fluorescence staining to evaluate the design effect of the Ortho-K lens.Finally,a Ortho-K lens customization software was developed.The software displays a schematic diagram of the reconstructed corneal structure,a schematic diagram of the customized Ortho-K,a tear film thickness curve,and a simulated fluorescence staining diagram.Users of the software can modify the design parameters of Ortho-K lens to achieve personalized customization.The software was developed using a mix of Qt and MATLAB programming.