Background and objective

Glaucoma is currently a major cause for irreversible blindness worldwide. A risk factor and the only therapeutic control parameter is the intraocular pressure (IOP). The IOP is determined with tonometers, whose measurements are inevitably influenced by the geometry of the eye. Even though the corneal mechanics have been investigated to improve accuracy of Goldmann and air pulse tonometry, influences of geometric properties of the eye on an acoustic self-tonometer approach are still unresolved.

Methods

In order to understand and compensate for measurement deviations resulting from the geometric uniqueness of eyes, a finite element eye model is designed that considers all relevant eye components and is adjustable to all physiological shapes of the human eye.

Results

The general IOP-dependent behavior of the eye model is validated by laboratory measurements on porcine eyes. The difference between simulation and measurement is below 8 µm for IOP levels from 5 to 40 mmHg. The adaptive eye model is then used to quantify systematic uncertainty contributions of a variation of eye length and central corneal thickness based on input statistics of a clinical trial series. The adaptive eye model provides the required relation between biometric eye parameters and the corneal deflection amplitude, which here is the measured quantity to trace back to the IOP. Implementing the relations provided by the eye model in a Gaussian uncertainty propagation calculation now allows the quantification of the uncertainty contributions of the biometric parameters on the overall measurement uncertainty of the acoustic self-tonometer. As a result, a systematic uncertainty contribution resulting from deviations in eye length dominate stochastic deviations of the sensor equipment by a factor of 3.5.

Conclusion

As perspective, the proposed adaptive eye model provides the basis to compensate for systematic deviations of (but not only) the acoustic self-tonometer.

中文翻译：

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自适应有限元眼模型，可补偿对声压计的生物特征影响

背景和目标

青光眼目前是全世界不可逆性失明的主要原因。危险因素和唯一的治疗控制参数是眼内压（IOP）。IOP由眼压计确定，其测量不可避免地受到眼睛几何形状的影响。尽管已经研究了角膜力学以提高Goldmann和空气脉冲眼压计的准确性，但仍未解决眼睛的几何特性对声学自眼压计方法的影响。

方法

为了理解和补偿由于眼睛的几何唯一性而导致的测量偏差，设计了一种有限元眼模型，该模型考虑了所有相关的眼组件，并且可以适应人眼的所有生理形状。

结果

眼模型的一般IOP依赖性行为已通过实验室对猪眼的测量得到了验证。对于5至40 mmHg的IOP，模拟与测量之间的差异在8 µm以下。然后，根据临床试验系列的输入统计数据，将自适应眼模型用于量化眼长和角膜中央厚度变化的系统不确定性贡献。自适应眼模型提供了生物特征眼参数与角膜偏转幅度之间的所需关系，这是可追溯到IOP的测量量。现在，通过在高斯不确定性传播计算中实施眼图模型提供的关系，就可以量化生物特征参数对声学自眼压计的总体测量不确定性的不确定性贡献。

结论

从角度来看，所提出的自适应眼图模型为补偿（但不仅限于）声学自眼压计的系统偏差提供了基础。