Corneal astigmatism axis standard based on toroidal surface design

Jiyan Zhang; Wenli Liu; Baoyu Hong; Lei Yang; Xiang Ding; Mingliang Gao

doi:10.1117/12.2505554

15 November 2018 Corneal astigmatism axis standard based on toroidal surface design

Jiyan Zhang, Wenli Liu, Baoyu Hong, Lei Yang, Xiang Ding, Mingliang Gao

Proceedings Volume 10964, Tenth International Conference on Information Optics and Photonics; 1096420 (2018) https://doi.org/10.1117/12.2505554
Event: Tenth International Conference on Information Optics and Photonics (CIOP 2018), 2018, Beijing, China

Abstract

Cornea is an important part of human eye refractive system. Corneal astigmatism axis, as a key parameter to evaluate the corneal topography, is directly related to visual diagnosis and treatment. In 1997, International Organization for Standardization published the first ISO standard for requirements of corneal parameter measurement. However, due to the limitation of processing and testing technology at that time, the standard of corneal astigmatism axis has been an unsolved technical problem. Research work on corneal astigmatism axis standard was carried out early in 2007 by China National Institute of Metrology. In this paper, first, measurement principle of corneal parameter is described. Then, corneal astigmatism axis standard based on toroidal surface is designed and manufactured, which consists of axial model eye, axial sleeve and measurement support. Axial model eye is a square cylinder whose front surface is toroidal and back surface is scrub plane, which is located in the square through hole of axial sleeve, and axial sleeve is located on the trapezoid groove of measurement support. Next, by accurate measurement and metrological calibration, four axes of 0°, 45°, 90° and 135° are achieved and axis uncertainty U=0.3° (k=2). Finally, measurement results show that the newly developed astigmatism axis standard can realize the evaluation of corneal parameter testing instruments well. Besides, design structure specified in ISO standard is found to be hard for accurately location and infeasible in practice. A proposal for revision of this international standard will be drafted and discussed on ISO meeting of 2019 held in America.

Citation Download Citation

Jiyan Zhang, Wenli Liu, Baoyu Hong, Lei Yang, Xiang Ding, and Mingliang Gao "Corneal astigmatism axis standard based on toroidal surface design", Proc. SPIE 10964, Tenth International Conference on Information Optics and Photonics, 1096420 (15 November 2018); https://doi.org/10.1117/12.2505554

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KEYWORDS

Standards development

Cornea

Eye

Tolerancing

Eye models

Metrology

Calibration

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