Abstract An apparatus and process for measuring optometric spherical and cylindrical optic correction to the eye is disclosed. Typically, two pairs of counter-rotating positive and negative cylindrical lenses are actually used or optically emulated. As actually used, each positive cylindrical lens is counter-rotated relative to its paired negative cylindrical lens. These counter-rotating positive and negative cylindrical lenses produce variable positive and negative cylinder power relative to two axes substantially orthogonal to the optical axis of the lens instrument. Each pair of cylinders is aligned and counter-rotated relative to the remaining pair of cylinders to generate its positive cylinder and negative cylinder along the optical axes at a non-coincident angle (preferably precisely 45* removed) from the corresponding axes of the remaining counter-rotating lens pair. By choosing preselected positions of counter-relative rotation between the paired lens elements of each pair, virtually all optically practical angles and powers of cylindrical lens astigmatism correction can be generated independent of the spherical optical properties of any ocular lens train. Provision is made for the emulation of counter-rotating lens pairs by the insertion of the lens elements having variable astigmatic and spherical powers with the aforementioned optical properties. The process includes a Cartesian coordinate plot for describing astigmatic correction with reduced error, especially at low cylinder power and a process of determining correction required to existent and known prescriptions.
A process for describing astigmatic effects of a cylinder lens in power and variable rotational alignment relative to a preselected view path on a patient having vision correction of a cylindrical prescription of known power and known angular rotation, said process comprising the steps of: providing a patient viewing statiOn; providing an image to be viewed along a light path to said image; placing said cylinder prescription of known power and known rotation between eyes of said patient and said view path; determining cylindrical lens power and angle of said patient as viewing said target through said prescription; providing a coordinate plot having first and second axes; plotting on said coordinate the vector of the power and doubled angle of cylinder of said known cylindrical prescription; plotting from said vector the determined cylinder power and doubled angle of said patient through said known prescription; locating on said coordinate plot a coordinate point relative to said first and second axes to determine the power and doubled angle of said corrected prescription.
Claim 2
Dependent Claim
170 words
A process for describing astigmatic effects of a cylinder lens in power and variable rotational alignment relative to a preselected view path on a patient having vision correction of a cylindrical prescription of known power and known angular rotation, said process comprising the steps of: providing a patient viewing statiOn; providing an image to be viewed along a light path to said image; placing said cylinder prescription of known power and known rotation between eyes of said patient and said view path; determining cylindrical lens power and angle of said patient as viewing said target through said prescription; providing a coordinate plot having first and second axes; plotting on said coordinate the vector of the power and doubled angle of cylinder of said known cylindrical prescription; plotting from said vector the determined cylinder power and doubled angle of said patient through said known prescription; locating on said coordinate plot a coordinate point relative to said first and second axes to determine the power and doubled angle of said corrected prescription.