目的：比较不同受检者在相同近视屈光欠矫下使用 C 字视力表和 E 字视力表所测得的视力差别及探讨导致这种差别的原因。方法：选取不同年龄段 250 名受检者，在完全矫正屈光度 [最正之最佳视力 (maximum plus to maximum visual acuity，MPMVA)] 情况下附加相应的球镜造成相应的近视度数后比较使用2种不同的视力表测出的视力值变化情况。同时根据2种视力表的设计原理及视力表的不同记录法探讨造成数值不同的可能原因。结果：同一附加度情况下分别用C字视力表组和E字视力表组行方差分析，不同年龄组间差异无统计学意义(P > 0.05)。相同附加度情况下同一受检者使用C字视力表组和E字视力表组行t检验，两者差异具有统计学意义(t = -15.798，P < 0.05)，C 字视力表测得视力平均值小于E字视力表测得视力平均值。结论：受检者使用 C 字视力表比 E 字视力表检测视力结果更加优异；C 字视力表和 E 字视力表的视标形状及开口方向不同是 2 种视力表检测结果差异的主要原因。

Objective: To compare the difference of visual acuity measured by C-chart and E-chart in the same myopic refractive undercorrection and to explore the causes of the difference. Methods: Two hundred and fifty subjects of different ages were selected to compare the changes of visual acuity measured by two different visual meters after adding corresponding spherical lenses to the maximum plus to maximum visual acuity (MPMVA) corrected diopter. At the same time, according to the design principle of the two kinds of visual acuity meters and the different recording methods of visual acuity tables, the possible reasons for the different values were discussed.Results: There was no significant difference between different age groups (P > 0.05). Under the same degree of additionality, the visual acuity of the same subjects was tested by t-test with C visual acuity chart and E visual acuity chart. The difference was statistically significant (t = -15.798, P < 0.05). The average visual acuity of C visual acuity table was smaller than that of E visual acuity table. Conclusion: The visual acuity of myopic patients tested by C visual acuity chart is better than by E visual acuity chart. The main reason for the difference between C visual chart and E visual chart was the different shape and opening direction of visual icons.

目的：比较学生在不同散光欠矫下使用C字视力表和E字视力表所测的视力差别并分析其原因。

方法：选取 30 名 15~18 岁的学生，在完全矫正屈光度 MPMVA（maximum plus to maximum visual acuity）状态下，附加相应不同散光轴向的柱镜造成相应的散光度数后，比较使用两种不同的视力表测出的视力值。同时根据两种视力表不同的设计原理及记录方法，分析造成数值差异的可能原因。

结果：与 E 字视力表组相比，C 字视力表组附加各个轴向 +0.25 DC 柱镜组测得视力值均值差异较小，附加 +0.50 DC 差异较大，其中斜轴方向上的差异更大，差异有统计学意义（F = 23.141，P < 0.01）。在各个附加度组别中使用 C 字视力表测得视力平均值小于 E 字视力表测得视力平均值，其中斜轴方向的附加组差值更大。C 字视力表在各散光轴位测得视力值差异无统计学意义（F = 1.446，P = 0.231）；E 字视力表组在各散光轴位测得视力值相差明显，在斜轴散光中数值与非斜轴散光数值差异有统计学意义。

结论：散光患者使用 C 字视力表更加优异，不同轴向的散光测出来的视力值更加稳定。对于非斜轴散光患者来说，使用 C 字视力表比 E 字视力表更难，用小数记录法记录视力值可能相差 3 ~ 4 行，原因为散光眼在各个方向上的屈光度不一致及 C 字视力表和 E 字视力表的视标形状及排列不同导致。

Objective: To compare the differences of visual acuity measured by C-chart and E-chart under different astigmatism and analyze the reasons for the differences.

Methods: Thirty students aged 15–18 years were selected. Under the condition of fully corrected refractive MPMVA (maximum plus to maximum visual acuity)，the corresponding astigmatism was caused by adding corresponding columnar lenses with different astigmatism axes. The corresponding visual acuities measured by two different visual charts. According to the design principle and recording methods of two kinds of visual acuity charts, the possible reasons for the different values are analyzed.

Results: Compared with the E-type visual acuity chart, the average difference of visual acuity measured by adding each axis +0.25 DC columnar lens group was smaller, and the difference between adding +0.50 DC group was larger, especially in the oblique axis direction（F = 23.141，P < 0.01）。The average visual acuity measured by the C-type visual acuity chart in each additional degree group was smaller than that measured by the E-type visual acuity chart, and the difference of the additional group in the oblique axis direction was greater than that measured by the E-type visual acuity chart. There was no significant difference in the visual acuity measured by C-type chart at different astigmatism axes（F = 1.446，P = 0.231）；there was a significant difference in the visual acuity values measured by E-type chart at different astigmatism axes, and there was a significant difference in the values of oblique astigmatism and non-oblique astigmatism.

Conclusion: Astigmatism patients with C-type chart obtain more accurate results, and the visual acuity values measured by different axes of astigmatism are more stable. For patients with non-oblique astigmatism, it is more difficult to use C-type chart than E-type chart. The difference of visual acuity recorded by decimal recording method may be 3–4 rows. The reasons are the inconsistency of diopter in different directions of astigmatism and the different shape and arrangement of visual icons between C- and E-type charts.

目的：比较不同受检者在相同近视屈光欠矫下使用C字视力表和E字视力表所测得的视力差别及探讨导致这种差别的原因。方法：选取不同年龄段250名受检者，在完全矫正屈光度[最正之最佳视力(maximum plus to maximum visual acuity，MPMVA)]情况下附加相应的球镜造成相应的近视度数后比较使用2种不同的视力表测出的视力值变化情况。同时根据2种视力表的设计原理及视力表的不同记录法探讨造成数值不同的可能原因。结果：同一附加度情况下分别用C字视力表组和E字视力表组行方差分析，不同年龄组间差异无统计学意义(P>0.05)。相同附加度情况下同一受检者使用C字视力表组和E字视力表组行t检验，两者差异具有统计学意义(t=?15.798，P<0.05)，C字视力表测得视力平均值小于E字视力表测得视力平均值。结论：受检者使用C字视力表比E字视力表检测视力结果更加优异；C字视力表和E字视力表的视标形状及开口方向不同是2种视力表检测结果差异的主要原因。

Objective: To compare the difference of visual acuity measured by C-chart and E-chart in the same myopic refractive undercorrection and to explore the causes of the difference. Methods: Two hundred and fifty subjects of different ages were selected to compare the changes of visual acuity measured by two different visual meters after adding corresponding spherical lenses to the maximum plus to maximum visual acuity (MPMVA) corrected diopter. At the same time, according to the design principle of the two kinds of visual acuity meters and the different recording methods of visual acuity tables, the possible reasons for the different values were discussed.Results: There was no significant difference between different age groups (P>0.05). Under the same degree of additionality, the visual acuity of the same subjects was tested by t-test with C visual acuity chart and E visual acuity chart. The difference was statistically significant (t=?15.798, P<0.05). The average visual acuity of C visual acuity table was smaller than that of E visual acuity table. Conclusion: The visual acuity of myopic patients tested by C visual acuity chart is better than by E visual acuity chart. The main reason for the difference between C visual chart and E visual chart was the different shape and opening direction of visual icons.