Particulate matter is composed of mobile, randomly sourced foreign substances (excluding bubbles), which cannot be quantitatively analyzed through chemical analysis due to their small quantity and uneven composition. Ophthalmic solutions should be essentially free of particles visible to the naked eye. The experiment described in this article is a physical test conducted to list foreign particles within a specific size range.

Unless otherwise specified in individual monographs, each ophthalmic solution shall comply with the particle limit specified in the test used. If higher limits are applicable, they will be specified in a separate monograph. As with medical devices, ophthalmic preparations as suspensions, emulsions or gel are not subject to these requirements. When testing applicability issues arise, please refer to specific monographs.

The photoresist method and microscopic counting method used to determine particulate matter in ophthalmic solutions are the same as those used for particle testing in injections; Therefore, in appropriate circumstances, andUSPGeneral Testing Chapter<788> Particulate Matter in InjectionsIt is mutually referenced. The testing method provided in this chapter is divided into two stages. Ophthalmic solutions are first processed using the photoresist procedure (Section)1Conduct testing during the stage. If the specified limit is not reached, a microscopic counting procedure must be performed (Section)2Stage) and its testing limits. If, due to technical reasons, it is not possible to test ophthalmic solutions using the photoresist method, only microscopic counting method can be used for testing. Documents are required to prove that the photoresist method cannot test ophthalmic solutions or produces invalid results.

It is expected that most samples will only meet the requirements based on photoresist testing; However, it may be necessary to conduct optical resistance tests first, followed by microscopic counting tests to obtain satisfactory conclusions. When analyzed using the photoresist counting method, any product that is not a pure solution and has transparency and viscosity close to water may provide incorrect data. This type of material can be analyzed by microscopic counting method. In some cases, the viscosity of the material to be tested may be high enough that it cannot be analyzed by any testing method. In this case, appropriate diluents can be used for quantitative dilution as needed to reduce viscosity for analysis.

In the experiments described below, the results obtained by examining individual units or groups of particles cannot be extrapolated to other untested units. Therefore, in order to draw effective inferences from observational data to characterize the levels of particulate matter in a large number of devices, a sampling plan must be developed based on known operational factors. The sampling plan needs to consider product volume and historyThe number of particles, size distribution of particles, and variability of particle counts between units compared to the limit value.