Department of Applied Physics, Aalto University, Otakaari 1M, 02150 Espoo, Finland.
Cont Lens Anterior Eye. 2011 Feb;34(1):2-6. doi: 10.1016/j.clae.2010.06.008. Epub 2010 Jul 17.
In this study, void size and free volume properties in different contact lens materials have been investigated in their hydrated state using positron annihilation lifetime spectroscopy (PALS).
PALS is used to characterize the void size distributions inside the lens materials. Three different types of contact lenses were used (Balafilcon A, Hilafilcon B and Polymacon).
Measurements on different contact lenses reveal significant differences between the materials, up to ∼ 100% difference in void volume was observed between Hilafilcon B and Balafilcon A, the latter having larger voids. As oxygen diffusion is strongly correlated with the void sizes, the results are in good agreement with the usage recommendations of the specific lens types (daily disposable lenses or 1 month continuous use lenses). The void sizes in monthly lenses (Balafilcon A) were found to decrease 25% under artificial aqueous tear (albumin-water solution) exposure in 4 weeks leading to a significant decrease in the oxygen permeation rate through the contact lens. Yet, the voids were still significantly larger than in disposable or semi-disposable lenses.
We have showed that PALS is a viable method to probe the microstructure of biotechnologically relevant polymers and can be used to quantify the void properties in different types of contact lenses. Usage recommendations correlate well with measured void sizes and the median void size decreases during the incubation of albumin solution as a function of time. We anticipate the use of PALS for any polymer-based intracorneal/intraocular device in which diffusivity plays a crucial role.
本研究采用正电子湮没寿命谱（PALS）研究了不同接触镜材料在水合状态下的空隙大小和自由体积特性。
PALS 用于表征镜片材料内部的空隙大小分布。使用了三种不同类型的隐形眼镜（Balafilcon A、Hilafilcon B 和 Polymacon）。
对不同隐形眼镜的测量显示出材料之间存在显著差异，在 Hilafilcon B 和 Balafilcon A 之间观察到高达 100%的空隙体积差异，后者具有更大的空隙。由于氧气扩散与空隙大小密切相关，因此结果与特定镜片类型的使用建议（日抛型或 1 个月连续使用型）非常吻合。在 4 周的人工泪液（白蛋白-水溶液）暴露下，每月更换型隐形眼镜（Balafilcon A）的空隙大小发现减少了 25%，导致氧气透过隐形眼镜的渗透速率显著降低。然而，空隙仍然明显大于一次性或半一次性隐形眼镜。
我们已经表明，PALS 是一种可行的方法，可以探测生物技术相关聚合物的微观结构，并可用于量化不同类型隐形眼镜的空隙特性。使用建议与测量的空隙大小很好地相关，并且在白蛋白溶液孵育过程中，随着时间的推移，中位数空隙大小会减小。我们预计 PALS 将用于任何基于聚合物的角膜内/眼内装置，其中扩散率起着至关重要的作用。
