Purpose: Ophthalmic prisms are routinely used to measure ocular deviation. However, large measurement errors could be induced when a prism is not accurately positioned at its calibration position. We report a simple way to minimize the errors. Methods: We measured powers of prisms and plastic prisms at their calibration position and at angles the prism was rotated away from the calibration position. Glass prisms that have power of 20, 25, 30, 40, 50, and 60 prism diopters (PD) and plastic prisms that has power of 20, 25, 30, 35, 40, 45, 50 PD were used. To minimize the errors, we developed a pair of prism frame so that the prism can always be positioned accurately. Results: We have demonstrated large errors induced by rotating glass prisms and plastic prism away from their calibration position. Larger errors were recorded with glass prisms than with plastic prisms. The measurement errors are significant even with a small angle rotation for a large power glass prism. For instance, a 10-degrees rotation of a 50PD glass prism produces an error of 30PD. However, measurements errors were minimized when the prism frame was used. Conclusion: It suggests that the glass ophthalmic prism should be abandoned and the use of ophthalmic prisms in strabismus measurement should be standardized with assistance of the prism frame.
| Published in | International Journal of Ophthalmology & Visual Science (Volume 6, Issue 1) |
| DOI | 10.11648/j.ijovs.20210601.19 |
| Page(s) | 59-62 |
| Creative Commons |
This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited. |
| Copyright |
Copyright © The Author(s), 2021. Published by Science Publishing Group |
Ophthalmic Prisms, Strabismus, Ocular Deviation
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| [3] | Kaye SB, Ansons AM, Green JR, Wylie J. The prism bar—Prentice and frontal positions. Eye 3: 404–408 (1989). |
| [4] | Irsch K. Optical Issues in Measuring Strabismus. Middle East Afr J Ophthalmol. 22: 265-70 (2015). |
| [5] | Yang D. et cl. Ophthalmic prisms: Optical measurement errors and a simple device to minimize the errors. AAPOS annual meeting, Vancouver, Canada, April 6-10, 2016. |
| [6] | Von Noorden GK, Campos EC. Binocular Vision and Ocular Motility: Theory and management of strabismus. 6th ed by Mosby. Page 190. |
| [7] | Freedman K, Ray C, Kirk D. Reevaluation of Current Prism Standards with Recommendations to Increase Accuracy in the Measurement of Strabismus. Am J Ophthalmol. 2019 Feb; 198: 130-135. |
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APA Style
Ping Wang, Ya Pan, Jie Zhang, Dongsheng Yang. (2021). Measurement Errors Induced by Inaccurate Positioning of Ophthalmic Prisms and a Simple Way to Minimize Them. International Journal of Ophthalmology & Visual Science, 6(1), 59-62. https://doi.org/10.11648/j.ijovs.20210601.19
ACS Style
Ping Wang; Ya Pan; Jie Zhang; Dongsheng Yang. Measurement Errors Induced by Inaccurate Positioning of Ophthalmic Prisms and a Simple Way to Minimize Them. Int. J. Ophthalmol. Vis. Sci. 2021, 6(1), 59-62. doi: 10.11648/j.ijovs.20210601.19
AMA Style
Ping Wang, Ya Pan, Jie Zhang, Dongsheng Yang. Measurement Errors Induced by Inaccurate Positioning of Ophthalmic Prisms and a Simple Way to Minimize Them. Int J Ophthalmol Vis Sci. 2021;6(1):59-62. doi: 10.11648/j.ijovs.20210601.19
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Download@article{10.11648/j.ijovs.20210601.19,
author = {Ping Wang and Ya Pan and Jie Zhang and Dongsheng Yang},
title = {Measurement Errors Induced by Inaccurate Positioning of Ophthalmic Prisms and a Simple Way to Minimize Them},
journal = {International Journal of Ophthalmology & Visual Science},
volume = {6},
number = {1},
pages = {59-62},
doi = {10.11648/j.ijovs.20210601.19},
url = {https://doi.org/10.11648/j.ijovs.20210601.19},
eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijovs.20210601.19},
abstract = {Purpose: Ophthalmic prisms are routinely used to measure ocular deviation. However, large measurement errors could be induced when a prism is not accurately positioned at its calibration position. We report a simple way to minimize the errors. Methods: We measured powers of prisms and plastic prisms at their calibration position and at angles the prism was rotated away from the calibration position. Glass prisms that have power of 20, 25, 30, 40, 50, and 60 prism diopters (PD) and plastic prisms that has power of 20, 25, 30, 35, 40, 45, 50 PD were used. To minimize the errors, we developed a pair of prism frame so that the prism can always be positioned accurately. Results: We have demonstrated large errors induced by rotating glass prisms and plastic prism away from their calibration position. Larger errors were recorded with glass prisms than with plastic prisms. The measurement errors are significant even with a small angle rotation for a large power glass prism. For instance, a 10-degrees rotation of a 50PD glass prism produces an error of 30PD. However, measurements errors were minimized when the prism frame was used. Conclusion: It suggests that the glass ophthalmic prism should be abandoned and the use of ophthalmic prisms in strabismus measurement should be standardized with assistance of the prism frame.},
year = {2021}
}
TY - JOUR T1 - Measurement Errors Induced by Inaccurate Positioning of Ophthalmic Prisms and a Simple Way to Minimize Them AU - Ping Wang AU - Ya Pan AU - Jie Zhang AU - Dongsheng Yang Y1 - 2021/03/17 PY - 2021 N1 - https://doi.org/10.11648/j.ijovs.20210601.19 DO - 10.11648/j.ijovs.20210601.19 T2 - International Journal of Ophthalmology & Visual Science JF - International Journal of Ophthalmology & Visual Science JO - International Journal of Ophthalmology & Visual Science SP - 59 EP - 62 PB - Science Publishing Group SN - 2637-3858 UR - https://doi.org/10.11648/j.ijovs.20210601.19 AB - Purpose: Ophthalmic prisms are routinely used to measure ocular deviation. However, large measurement errors could be induced when a prism is not accurately positioned at its calibration position. We report a simple way to minimize the errors. Methods: We measured powers of prisms and plastic prisms at their calibration position and at angles the prism was rotated away from the calibration position. Glass prisms that have power of 20, 25, 30, 40, 50, and 60 prism diopters (PD) and plastic prisms that has power of 20, 25, 30, 35, 40, 45, 50 PD were used. To minimize the errors, we developed a pair of prism frame so that the prism can always be positioned accurately. Results: We have demonstrated large errors induced by rotating glass prisms and plastic prism away from their calibration position. Larger errors were recorded with glass prisms than with plastic prisms. The measurement errors are significant even with a small angle rotation for a large power glass prism. For instance, a 10-degrees rotation of a 50PD glass prism produces an error of 30PD. However, measurements errors were minimized when the prism frame was used. Conclusion: It suggests that the glass ophthalmic prism should be abandoned and the use of ophthalmic prisms in strabismus measurement should be standardized with assistance of the prism frame. VL - 6 IS - 1 ER -
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