The Importance of Integrity Testing for Contact Lenses: ENSURING QUALITY AND SAFETY

Contact lenses have become increasingly popular over the years, offering a convenient and comfortable alternative to traditional eyeglasses. These small, curved discs of vision correction technology are designed to sit directly on the cornea, providing clear and accurate vision without the need for bulky frames. However, given their direct contact with one of the most sensitive parts of the human body, it is crucial to ensure the quality and safety of contact lenses. One of the key methods employed to achieve this is integrity testing.

THE CHALLENGE

Integrity testing plays a vital role in the manufacturing and distribution process of contact lenses, helping guarantee their quality, reliability, and overall performance. It involves a series of rigorous examinations and evaluations that assess the lenses' physical properties, structural integrity, and ability to meet specific standards and regulatory requirements. By subjecting contact lenses to comprehensive integrity testing protocols, manufacturers can detect and mitigate any potential defects or malfunctions that may compromise the wearer's visual health and safety.

In addition to quality control during the manufacturing process, integrity testing is essential throughout the supply chain, including packaging, transportation, and storage. These testing procedures verify that the lenses remain intact and unharmed during these stages, ensuring they reach the end-users in optimal condition. Moreover, integrity testing serves as a critical component of regulatory compliance in the contact lens industry. Regulatory bodies, such as the Food and Drug Administration (FDA) in the United States, mandate specific guidelines and standards that contact lens manufacturers must meet to ensure the safety and effectiveness of their products.

THE SOLUTION

Contact lens packaging is typically a liquid-filled, low headspace rigid polymer tray with a foil laminate lidding. The gaseous content is minimal creating difficulty for a variety of pressure differential-based technologies. PTI has created a dual technology test method utilizing vacuum decay and force decay. Force decay measurements are taken with thousands of sensors during a vacuum decay test cycle in accordance with ASTM F2338. Under the vacuum profile, package lidding expands and creates a dome. This dome exerts a force onto our sensor array. When a leak is present, lidding does not expand as air and liquid egress from the package. This may display 0 force reading or show a differential value pending the size of the leak and vacuum level. The test method reports absolute and differential readings for both vacuum and force with a high level of repeatability, sensitivity, and reliability.

THE RESULT

The results above display the absolute force of a series of negative and positive controls. Positive controls were created with steel wire defects to create a channel leak across the seal surface. Group C represents 30 negative controls while groups A and B represent 80 and 50 micron wire pull defects, respectively.

Integrity testing is vital for ensuring the quality, reliability, and safety of contact lenses throughout their entire lifecycle. It involves rigorous examinations and evaluations that help manufacturers detect and address any defects or hazards that could compromise the wearer's visual health. These tests assess the lenses' physical properties, structural integrity, and compliance with regulatory requirements, guaranteeing their performance and effectiveness.

Integrity testing extends beyond manufacturing to packaging, transportation, and storage stages. By subjecting contact lenses to dual technology test methods, such as vacuum decay and force decay, manufacturers can accurately detect leaks and ensure that the lenses reach end-users undamaged. This comprehensive testing approach, coupled with adherence to regulatory standards, demonstrates the commitment of manufacturers to quality control and provides consumers with reliable and safe products that deliver clear vision and maintain eye health.