目的推导散光表视标检查中30°原则的由来．方法根据光学和数学原理逐步推导被检查者所辨认的散光表视标清晰线所对应的钟点数与散光轴位之间的关系．结果被检者看到的散光表视标清晰线所对应的小钟点数乘以30，即该被检者的负柱镜轴位．结论散光表视标检查中30°原则的解析，有助于检查者正确的理解和使用散光表视标．%Objective To derive principle of 30 degree in astigmatic dials test. Methods Based on optical and mathematic principle, the relationship between astigmatic dials test result and astigmatism axis was calcu- lated out as a formula. Result Multiply the clock position of sharpest reported by the patient by 30 degree is the astigmatism axis of the patient. Conclusion This calculation is useful to understand and correctly use the astigmatic dials test.
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