Choice and recommendation of prismatic lens from the catalogue
Introduction
Prism lenses are used for correction strabismus and heterophoria. Prism lenses move the optical ray to base of the prismatic lens, which is thickest part of the lens. Prismatic correction can be realized by two ways. Firstly, we can decenter spherical or sphere-cylindrical lens during the centering and grinding. More exact method is ordering the prismatic effect on given lens which is produced by usage of special grinding ring or tilting of the grinding arm.
Goals
- For given spectacle frame choose and center proper prismatic lens from lens catalogue.
- For given patient release and evaluate prescription for optical aid.
- For given patient and prescription create financial plan for spectacles.
Equipment
Actual book of VZP, catalogue of spectacle lens producer, writing equipment, calculator, PD meter.
Methods
For given spectacle frame choose and center proper prismatic lens from lens catalogue.
Your task is to choose proper spectacle frame for you colleague (student) from spectacle book and proper spectacle lens. Correction could be for prismatic lens. In the protocol you should note all measured parameters and data of selection including boxing system, PD of the patient, height of the centration, vertex distance, name of the frame and lens, type of antireflection coating. You should of course calculate and note decentration and chosen lens diameter.
For given patient release and evaluate prescription for optical aid.
You should draw general prescription form into the protocol and fill in all important notes in it. Further you should financially evaluate the prescription.
For given patient and prescription create financial plan for spectacles.
In this task you should create financial evaluation of the prescription for patient, i.e. you will sum price for the spectacle frame, spectacle lenses, for addition task as e.g. repair of the side, soldering etc. is. From this sum you will subtract price for the prescription and define payment for advance and payment of the rest of the issue.
Results
For given spectacle frame choose and center proper prismatic lens from lens catalogue.
For given patient release and evaluate prescription for optical aid.
For given patient and prescription create financial plan for spectacles.
Discussion
In case of decentration of spherical or sphere-cylindrical lens for inducing of prism effect we are not able to maintain condition for point imaging. High prism effect we can only induce with strong power lens. High decentration cause different peripheral thickness of the lens which is not aesthetic. Manufactured prismatic lens should be shifted by 0.25 mm per 1 pD against the base of the lens because of maintaining of point imaging.
Conclusion, notes, comments
We have two types of decentration for prismatic lens. Explain the principal.
Why we do the decentration of the main point of prismatic lens in direction against the base of the lens (0.25 mm per 1 pD)?