USP <789> Particulate Matter in Ophthalmic Solutions

Test Methods (Manual Microscopic Focus): USP <789> employs a two-step testing approach. Stage 1 uses an automated Light Obscuration particle counter to screen for particles by size and count. If the product passes Stage 1, it meets the requirements. If Stage 1 fails or if the product is not suitable for light obscuration (e.g., it’s too viscous, opaque, or tends to produce air bubbles), then Stage 2 is performed – the Microscopic Particle Count Test. In the microscopic method, the solution is filtered through a fine membrane, and any particles retained on the filter are manually counted under a microscope by a trained analyst. We specialize in this manual microscopic inspection, which not only counts particles but also allows us to observe their morphology (shape, color, etc.). This can aid to identify what the particles are – for example, fibers, glass shards, or drug precipitates – something the automated counter cannot do.

Adhering to USP <789> ensures you are meeting the requirements of major regulators worldwide. The European Pharmacopoeia (EP) has equivalent tests for particulate contamination (EP chapter 2.9.19 for sub-visible particles) and is harmonized closely with the USP standards. The Japanese Pharmacopoeia (JP) similarly aligns on particle count criteria. Regulatory agencies like the U.S. FDA and Europe’s EMA expect ophthalmic products to comply with these compendial standards. In fact, USP <789> explicitly states that ophthalmic solutions must be essentially free of visible particles and controlled for subvisible particles, a principle echoed by EMA guidance as well. By complying with USP <789>, manufacturers facilitate smoother approvals in multiple markets and demonstrate a commitment to high quality.

Why does USP <789> matter?
Because particles in an eye product can harm patients. Even small particles can irritate the eye, cause discomfort, or blur vision. Larger or contaminated particles might scratch the cornea or introduce infection. In the case of intraocular injections (like for certain retina treatments), any particle can literally appear as a “floater” in the patient’s visual field or cause inflammation. Non-compliance with particulate limits can lead to product recalls, regulatory actions, and damage to your brand’s reputation, not to mention potential injury to patients. Thus, USP <789> is a key part of risk mitigation for ophthalmic therapies.

Meeting USP <789> is a lot more than just passing a test – it’s about building quality into your manufacturing process. We recommend clients on good particulate control practices to reduce risks, such as: using particle-free packaging components, implementing proper filtration and gowning in production to avoid fiber contamination, and monitoring equipment wear (to catch any shedding of glass or metal particles). Regulatory compliance in this area means your manufacturing process consistently produces ophthalmic solutions that stay within the USP <789> limits for particulates. If a batch fails the particulate criteria (exceeds the limits), it cannot be released for patient use. You would need to investigate and possibly report it to regulators, which can be costly and time-consuming. Our services assist you understand these compliance requirements and address common risk areas proactively. We also maintain familiarity with global updates on particulate matter regulations – for instance, changes in Pharmacopeia chapters or guidance documents – so we can keep your testing strategies up-to-date.

USP <789> compliance ensures your ophthalmic product is safe, high-quality and market-ready for a global patient population.