# 光散射式遮盖隐斜视量测技术Technique of Measuring the Heterophoria by Diffuser Cover Test

Abstract: Heterophoria is the relative deviation of two eyes’ line of sight when there is no binocular fusion. The binocular fusion image can be suppressed by some methods, for example, the subject looks at a distant target to cover one eye with a cover plate, and then the optometrist observes the other eye. If the uncovered eye deviates from the initial position, the subject may have heterophoria. Cover test is a very important method in clinical trials, which is often used to evaluate and diagnose non-strabismus binocular dysfunction, such as convergence insufficiency. Traditional clinical methods, such as the cover test or the modified Thorington test, are limited by subjective factors and cannot observe the movement of the heterophoria eye. In this study, the light scattering cover plate and eye position image capture device are used to measure the heterophoria, and 8051 single chip and PWM method are used to control the DC motor to drive the cover plate to complete the fast flip of the cover plate. The device is used for testing the alternation of two eyes covering and single eye covering, and can effectively carry out the heterophoria quick screen. The use of a CCD camera capture device and a motor to drive the optical diffuser cover plate to turn over can quickly and accurately check eye movements and other symptoms of eye diseases, which can suppress serious visual deterioration.

1. 引言

2. 原理

2.1. 双眼视觉

1) 感觉机转(sensory system)：主要功能是接受外界视觉的刺激，包括物体的形状、方位及颜色。整个运作包含了视觉系统在眼球解剖生理上的发育性、生理性成因及神经传导至大脑视觉皮质的影像形成等。

2) 整合机转(integrative system)：主要功能是将感觉机转汇整之视觉信息，融合形成单一视觉知觉区。视觉整合过程的融像作用影响其他机转运作，丧失或不足的融像能力也常因其他机转所造成。

3) 运动机转(motor system)：主要功能是眼外肌协调作用能力，除眼外肌作用外，与感觉机转的调节作用与瞳孔反应有密不可分的关联。运动机转障碍从外观很容易观察，而且常有明显症状产生。

Figure 1. The eye position offset after destroying the function of the two-eye fusion

Figure 2. Test flowchart cover-uncover

1) 遮盖~不遮盖测试

2) 交替遮盖测试

Table 1. Oblique type and direction

Figure 3. Schematic diagram of prism plus alternating cover test

2.2. 光散射片

Figure 4. Light scattering pattern

Figure 5. The relationship between the transmittance of light scattering sheet and the thickness of light scattering sheet

Figure 6. Three layers optical diffser

$L=\left({L}_{0}*\mathrm{cos}\theta \right)$

Figure 7. Lambert’s cosine law [12]

3. 系统架构

Figure 8. Measurement system structure

3.1. 光散射式遮眼装置

1) 水平翻转机构

(a) (b)

Figure 9. (a) Top view of horizontal turning mechanism; (b) Front view of horizontal turning mechanism

2) 垂直翻转机构

Figure 10. Front view of vertical turning mechanism

3.2. 光散射式遮盖板

Table 2. Specification of matte diffusing plate with fog surface structure

3.3. 眼位侦测与追踪

4. 实验方法与结果

4.1. 光散射式遮眼装置功能确认

Table 3. Light-diffuser cover the eye for the eye movement testing device

4.2. 隐斜视被检者测试

Table 4. 8ΔBO test data of subjects with heterophoria

Table 5. 5ΔBO test data of subjects with heterophoria

5. 结论

NOTES

*通讯作者。

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