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KMID : 1011420150200040501
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Journal of Korean Ophthalmic Optics Society
2015 Volume.20 No. 4 p.501 ~ p.509
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Evaluation of Reliability for Combined Refractive Power of Lenses in an Automatic Phoropter
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Lee Hyung-Kyun
Kim So-Ra
Park Mi-Jung
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Abstract
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Purpose: To evaluate the reliability of refractive power by comparing the marked refractive power in an automatic phoropter and actually measured spherical/cylindrical refractive power.
Methods: Actual refractive power of minus spherical lens and cylindrical lens in an automatic phoropter was measured by a manual lensmeter and compared with the accuracy of marked refractive power. Furthermore, combined refractive power and spherical equivalent refractive power of two overlapped lenses were compared and evaluated with the refractive power of trial lens.
Results: An error of 0.125 D and more against the marked degree was observed in 70.6% of spherical refractive power of spherical lens which is built in phoropter, and the higher error was shown with increasing refractive power. Single cylindrical refractive power of cylindrical lens is almost equivalent to the marked degree. Combined spherical refractive power was equivalent to spherical refractive power of single lenswhen spherical lens and cylindrical lens were overlapped in a phoropter. Thus, there was no change in spherical refractive power by lens overlapping. However, there was a great difference, which suggest the effect induced by overlapping between cylindrical refractive power and the marked degree when spherical lens and cylindrical lens were overlapped. Spherical equivalent refractive power measured by using a phoropter was lower than that estimated by trial glasses frame and marked degree. The difference was bigger with higher refractive power.
Conclusions: When assessment of visual acuity is made by using an automatic phoropter for high myopes or
myopic astigmatism, some difference against the marked degree may be produced and they may be overcorrected
which suggests that improvement is required.
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KEYWORD
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Automatic phoropter, Trial lens, Combined refractive power, Spherical equivalent refractive power, Reliability
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