du Toit Rènée, Soong Katherine, Brian Garry, Ramke Jacqueline
International Centre for Eyecare Education (ICEE), Sydney, Australia.
Optom Vis Sci. 2006 Aug;83(8):582-8. doi: 10.1097/01.opx.0000230270.39804.54.
The advantages of a focometer (FOCOMETER) over other methods of refraction for use in developing countries are that it is lightweight, compact, relatively inexpensive, fairly quick, and easy to use with minimal training. This clinical trial compared the repeatability, validity, and ease of use of the focometer with an autorefractor.
The refractive status of the right eye of 80 participants was determined with an autorefractor (Canon RK3). Three measurements were also taken with the focometer.
The spherical equivalent (M) of the focometer was 0.25 D more positive than the autorefractor (p < 0.001) and 84% of measurements were within 0.75 D of the autorefractor. The autorefractor detected astigmatism in 91% (73) of the eyes, whereas the focometer identified only 32% (26). The design of the clock target restricts cylinder axis accuracy to the nearest 15 degrees . There was evidence of a learning effect for the focometer: the second and third measurements were more repeatable in the untrained group. There were no differences between the mean (1.03 +/- 2.28) and third focometer (-1.05 +/- 2.32) measurements (p = 0.34). However, using the third focometer measurement, 94% of participants had visual acuities of at least 6/12(-2).
This study highlighted the focometer's restricted power range, inaccuracy of astigmatism and axis determination, and dependence on subject understanding and compliance. Therefore, in most clinical settings, the focometer would not be adequate for quantifying refractive error, but the focometer spherical equivalent was within acceptable limits of the autorefractor, and the visual acuity with lenses determined by the focometer indicates its potential usefulness in public health settings, especially where only spherical ready-made spectacles are dispensed. There may be more cost-effective ways to determine refractive error in these circumstances. A potentially important enhancement in focometer methodology that improves its ease of use was identified: use only the third measurement for each eye.
在发展中国家，验光仪（FOCOMETER）相较于其他验光方法的优势在于其重量轻、体积小、相对便宜、操作较快，且经过最少培训即可轻松使用。本临床试验比较了验光仪与自动验光仪的可重复性、有效性及易用性。
使用自动验光仪（佳能RK3）测定80名参与者右眼的屈光状态。同时使用验光仪进行三次测量。
验光仪的等效球镜度（M）比自动验光仪高0.25 D（p < 0.001），84%的测量值与自动验光仪的差值在0.75 D以内。自动验光仪检测出91%（73只）眼睛存在散光，而验光仪仅识别出32%（26只）。时钟视标的设计将柱镜轴位精度限制在最接近的15度。有证据表明验光仪存在学习效应：在未受过训练的组中，第二次和第三次测量的可重复性更高。第一次（1.03 +/- 2.28）和第三次验光仪测量值（-1.05 +/- 2.32）之间无差异（p = 0.34）。然而，使用第三次验光仪测量值时，94%的参与者视力至少为6/12（-2）。
本研究突出了验光仪的功率范围受限、散光及轴位测定不准确，以及对受试者理解和配合的依赖。因此，在大多数临床环境中，验光仪不足以用于量化屈光不正，但验光仪的等效球镜度在自动验光仪的可接受范围内，且通过验光仪确定镜片后的视力表明其在公共卫生环境中具有潜在用途，特别是在仅分发球面现成眼镜的情况下。在这些情况下，可能有更具成本效益的方法来确定屈光不正。确定了一种可能重要的验光仪方法改进，可提高其易用性：每只眼睛仅使用第三次测量值。
