Contact lenses are directly placed on the cornea of the human eye, which makes the choice of lens material a critical factor for wearers. Due to the influence of advertising, many users tend to focus on high water content lenses, believing that higher water content equals better quality. However, this is a common misconception. The most important factor in determining the comfort and safety of contact lens wear is oxygen permeability. The level of oxygen transmission affects both the duration of wear and the overall comfort of the lens.
To accurately measure oxygen permeability, the International Organization for Standardization (ISO) has developed testing standards, specifically ISO 9913-2. This standard is designed for rigid lenses and non-hydrogel flexible contact lenses. It measures key parameters such as oxygen flux (J), oxygen permeability (Dk), and oxygen transmissibility (Dk/t). These values help determine how effectively a lens allows oxygen to pass through, which is crucial for maintaining eye health during extended wear.
The testing process involves placing the sample in a specialized chamber. The upper chamber is filled with an oxygen-rich gas, while the lower chamber contains a carrier gas that flows into a Coulomb sensor. Oxygen diffuses through the lens based on the concentration gradient, and the sensor measures the amount of oxygen transferred. This data is used to calculate the oxygen permeability of the material. Before conducting tests, the equipment must be calibrated using a reference membrane, such as SRM 1470, which is also used in other standards like ASTM D 3985.
Currently, the TOY-C2 Oxygen Permeator from Jinan Languang Electromechanical Technology Co., Ltd. (Labthink) is widely recognized for its precision in contact lens oxygen permeability testing. This device offers temperature control ranging from 5°C to 95°C, ensuring accurate results under various conditions. Labthink’s Barrier Lab provides additional support, offering detailed testing and consulting services to contact lens manufacturers.
The testing procedure typically includes purging the system, introducing oxygen into the test chamber, allowing the system to stabilize, and then recording the results. There are notable differences between contact lens testing and soft packaging tests. For instance, the sample clamping mechanism and the size of the samples differ significantly. Additionally, the test environment plays a key role—standard films are usually tested at 23°C, but contact lenses are often tested at 35°C to simulate real-world use. Since temperature can greatly affect oxygen permeability measurements, maintaining stable conditions during testing is essential.
Oxygen permeability is a vital performance indicator for contact lenses. It directly impacts the wearer's comfort and long-term eye health. With the support of Labthink’s world-renowned barrier laboratory, Jinan Languang provides professional oxygen permeability testing equipment to contact lens manufacturers. The company aims to foster collaboration within the industry to support the growth and development of the Chinese contact lens market.
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