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Effect On Optometry For Decentration And Tilt Of Lenses In Phoropters
Sep 27, 2017

A scientific and normative optometry by comparatively analyzing the differences of refractory between subjective optometry by compositive eye refractometer and common optometry before and after cycloplegia.

Methods A total of 108 myopia patients, who were taking refractory examination aged from 17 to 28 years old, were enrolled from our department in August 2009. All patients were taking objective optometry by computer eye refractometer or ophthalmoscope before and after cycloplegia, and then operated with subjective optometry by compositive eye refractometer and common optometry.

The data were taken with statistical analysis by SPSS 11.0. Results Subjective optometry by compositive eye refractometer showed no difference between spheral lens degree and cylindrical lens degree before and after cyclop1egia (both P>0.05), but there was statistical difference in spheral lens degree by common optometry between before and after cycloplegia (P<0.01).

No difference was found in cylindrical lens degree between before and after mydriasis (P >0.05). Conclusions For adult patients with ametropia, scientific and normative compositive eye refractometer is a simple, reliable and accurate way for optometry. It can help patients to get correct ametropia without mydriasis and relaxing ciliary muscle.

The basic principle of geometric optics and ophthalmic dioptrics, the effect on decentration and tilt of lenses in phoropters is analyzed theoretically and verified by ZEMAX software. Results show that decentration in lenses will introduce extra prismatic power, and tilt will introduce error not only in prismatic power but also in spherical and cylindrical power. Moreover, if front and back surface of one single lens are tilted from two opposite directions, the error will be much bigger than that tilted from the same direction. Besides, the effect of decentration is a little more significant than that of tilt in assembly. Therefore, decentration and tilt from two opposite directions for front and back surface of a lens should be avoided possibly in production and assembly of phoropters.

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