Design And Progress Of Progressive Addition Lenses For Myopia To Presbyopia Population

Traditional single-vision ophthalmic lenses can no longer meet the growing demand of patients with presbyopia in terms of comfort,effective field of vision,clarity and other aspects.Progressive addition lenses(PALs)are favored by more and more patients with presbyopia because of their ability to provide clear visual fields at distance,mid and near.The size of the distance and near zones is related to the design of the meridian,the contour line,and the sagittal height equation of the progressive plane.Therefore,this paper proposes a method of constructing progressive surface sagittal height,which uses a toric surface equation with curvature adjustment elements to design progressive addition lenses in order to reduce the astigmatism of the ophthalmic lenses and expand the effective visual field in the the near zone.The specific content is as follows:First,the paper analyzes the causes of presbyopia and the principle of eye adjustment and describes refractive anomalies and methods of corrections in the human eye.From the development of progressive addition lenses,the current status of domestic and international research are introduced.Next,the basic structure,function,their design types such as hard and soft designs and typical direct design methods of progressive addition lens are briefly introduced.Then,Winthrop method is used to design the meridian,contour line and the center of curvature.In addition,evaluation indexes of progressive addition lenses are stated.According to the characteristics of the toric surface that can adjust the curvature in the x and y directions respectively,it is proposed to design the vector height of progressive addition lens using the toric surface equation.The optical power and astigmatism distribution obtained by the spherical equation and the toric equation,which are compared to verify the feasibility of the toric surface equations in the design of progressive addition lenses.Finally,the designed spherical and the toric surface progressive addition lenses are manufactured using the VFT machine from Satisloh,and the optical power and astigmatism distribution of the two lenses are measured using the Rotlex Free Form Verifier(FFV).The results show that the toric progressive addition lenses outperformed the spherical progressive addition lenses.