Traditionally, ocular irritation testing has been conducted using rabbits. One purpose of this test is to evaluate any opacity caused by the test substance in the cornea of the eye and to measure it. Any disruption to the pigmented iris surrounding the pupil, which is deeper within the eye than the cornea, is also measured, and the conjunctiva or tissue surrounding the eye is evaluated for redness, chemosis and discharge. Different designations are used to classify the various physiological responses—i.e., Draize, European Union (EU), Globally Harmonized System (GHS), US Environmental Protection Agency (EPA), Hazardous Materials Identification System (HMIS), Federal Hazardous Substances Act (FHSA), etc.; using the same animal data but with different weights given to the various responses measured, as well as different overall approaches to statistical analysis.
Ocular irritation is distinguished from ocular corrosion based on reversibility. If, after 14 days, there is still an irritant response, the substance is classified as corrosive, but if the effect has reversed, the substance is classified as an irritant. The irritancy classification systems described above typically include substances that are corrosive within their most severe class—i.e., GHS and EPA “Cat I” or EPA “R41.” Ocular irritation is generally considered a less severe class, i.e., GHS “Cat 2A” and “Cat 2B”; EPA “Cat II” and “Cat III”; and EU “R36.” Nonirritant classes are listed as GHS “NC”, EPA “Cat IV” and EU “NC”.
The testing of personal care products for ocular irritancy ensures their safety, proper labeling and consumer satisfaction. In relation, there is a current demand for animal-alternative tests. Thus, described here is a method using synthetic tissue to test for mild, moderate and severe ocular irritation, including data validating this method as an effective means to screen products.
This content is adapted from an article in GCI Magazine. The original version can be found here.