Healthy guinea pigs secrete a white, milky liquid from their eyes which is used to both lubricate the eyes and clean their skin. After the "eye soap" is secreted, a piggy will use their front feet to spread it around their face with a washing motion. This is one of several reasons that guinea pigs don't require regular bathing, they're clever enough to do it themselves.
This is something we've seen many times but have never had the opportunity to photograph before. Thank you, Olly, for waiting for us to run and grab a camera before continuing with your daily grooming routine