School of Optometry and Vision Science, The University of New South Wales, Sydney, NSW, Australia.
Ophthalmic Physiol Opt. 2013 Mar;33(2):104-13. doi: 10.1111/opo.12025.
Assessment of corneal sensory function is more frequently being carried out using novel non-contact methods, which promise better stimulus control and a greater intensity range than more traditional techniques. An examination of the characteristics of the air-jet stimulus of these 'non-contact' aesthesiometers is important to enable an understanding of how these instruments stimulate the cornea. The purpose of this study was to model the air-jet stimulus of the CRCERT-Belmonte Aesthesiometer (CBA) and its interaction with the cornea.
A computerised simulation was used to model the CBA stimulus and this model was then examined in the context of verbal descriptions of the supra-threshold stimulus provided by 27 human subjects with normal corneas. The computational fluid dynamics model and the subjective descriptions considered CBA airflow values between 70 and 400 mL min(-1) .
The computational fluid dynamics results showed that the CBA air-jet stimulus behaves as expected in terms of force exerted and stabilises and subsides quickly during the 1 s duration for which it is turned on/off. The computer modelling demonstrated that the stimulus of the CBA consists of a central core of air flow, similar in diameter to the CBA nozzle, which exerts maximum pressure at the corneal apex. This core is surrounded by a less prominent zone of lower pressure, extending out to the corneal periphery at higher flow rates. The computer modelling results were confirmed by the subjective descriptions of intensity and corneal area stimulated, whereas relation to duration of sensation was more equivocal.
The CBA probably stimulates sensory receptors over a greater area of the ocular surface compared to the traditional nylon filament aesthesiometer and may recruit neurons sensitive to additional stimulus modalities. Future computational models should also incorporate temperature as an important aspect of the corneal response. This study has effectively demonstrated that it is possible to create a virtual model of an air-jet aesthesiometer stimulus using computational methods and that this model is corroborated by subjective descriptions provided by subjects.
目前，人们越来越多地使用新型非接触方法来评估角膜感觉功能，这些方法比传统技术更能更好地控制刺激强度范围。因此，了解这些“非接触”角膜感觉计的空气喷射刺激特性对于理解这些仪器如何刺激角膜非常重要。本研究的目的是模拟 CRCERT-Belmonte 角膜感觉计（CBA）的空气喷射刺激及其与角膜的相互作用。
使用计算机模拟来模拟 CBA 刺激，然后根据 27 名正常角膜受试者提供的超阈值刺激的口头描述来检查该模型。计算流体动力学模型和主观描述考虑了 70 至 400 毫升/分钟之间的 CBA 气流值。
计算流体动力学结果表明，CBA 空气喷射刺激在力的施加和稳定性方面表现符合预期，并且在 1 秒的开启/关闭时间内迅速消退。计算机建模表明，CBA 的刺激由空气流的中心核心组成，其直径与 CBA 喷嘴相似，在角膜顶点处施加最大压力。该核心周围是一个压力较低的不太明显区域，在较高的流速下延伸到角膜周边。计算机建模结果得到了强度和刺激角膜区域的主观描述的证实，而与感觉持续时间的关系则更为不确定。
与传统的尼龙纤维感觉计相比，CBA 可能会刺激更大面积的眼表面的感觉受体，并且可能会募集对其他刺激模式敏感的神经元。未来的计算模型还应将温度纳入角膜反应的重要方面。本研究有效地证明了使用计算方法创建空气喷射感觉计刺激的虚拟模型是可行的，并且该模型得到了受试者提供的主观描述的证实。
