Ahn Jihye, Choi Moonsung
Department of Optometry, College of Energy and Biotechnology, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea.
Convergence Institute of Biomedical Engineering and Biomaterials, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea.
Heliyon. 2023 Jan 20;9(2):e12996. doi: 10.1016/j.heliyon.2023.e12996. eCollection 2023 Feb.
The degree of protonation of contact lens materials is affected by the surrounding pH environment, due to the different pK values. The swelling of ionic contact lenses is generally controlled by these factors which determines physical properties of contact lenses. The purpose of this study was to evaluate the pH dependence of the physical properties of contact lenses. The ionic etafilcon A and non-ionic hilafilcon B contact lenses were used in this study. The diameter, refractive power, equilibrium water content (EWC), and the amounts of freezable-free water (W), freezable-bound water (W) and non-freezable water (W) in the contact lens at each pH condition were measured. The diameter, refractive power and EWC of etafilcon A decreased with decreasing pH below 7.0 or 7.4, whereas hilafilcon B showed relatively constant values. The quantity of W tended to increase with increasing pH, showing a relatively constant value above 7.0, whereas W decreased. Hilafilcon B did not show changes in EWC and specific trends in W and W. The significant change of etafilcon A at more acidic condition is derived from the presence of methacrylic acid (MA) which makes it vulnerable to pH. Additionally, though the EWC is composed of various states of water, (i) various states of water could response to surrounding environment in different way with EWC and (ii) W could be the crucial factor that determines physical properties of contact lens.
由于不同的pK值，隐形眼镜材料的质子化程度受周围pH环境的影响。离子型隐形眼镜的肿胀通常由这些决定隐形眼镜物理性质的因素控制。本研究的目的是评估隐形眼镜物理性质的pH依赖性。本研究使用了离子型依他氟康A和非离子型希拉氟康B隐形眼镜。测量了每种pH条件下隐形眼镜的直径、屈光力、平衡含水量（EWC）以及可冷冻自由水（W）、可冷冻结合水（W）和不可冷冻水（W）的含量。当pH值降至7.0或7.4以下时，依他氟康A的直径、屈光力和EWC下降，而希拉氟康B的值相对恒定。W的量倾向于随pH值升高而增加，在7.0以上显示相对恒定的值，而W下降。希拉氟康B的EWC没有变化，W和W也没有特定趋势。依他氟康A在更酸性条件下的显著变化源于甲基丙烯酸（MA）的存在，这使其易受pH值影响。此外，虽然EWC由各种水状态组成，（i）各种水状态可能以不同方式对周围环境做出反应，且EWC和（ii）W可能是决定隐形眼镜物理性质的关键因素。
