There is an interesting relationship between altmetrics and open access. One could even refer to altmetrics as open metrics. This is mainly due to the fact that altmetrics data uses open sources.
"For decades, the most common metric for evaluating research impact has been the number of times a research article is cited by other articles. This metric is sometimes represented by the raw count of citations received by the specific article in question or sometimes through an impact-by-association proxy – the number of citations received by the journal that published the article, summarized using a formula called the journal impact factor.
Citations are not the only way to represent the impact of a research article. A few alternative indicators have been the subjects of webometrics and bibliometrics research for years, including download counts and mentions in patents. However, as scholarly communication moves increasingly online, more indicators have become available: how many times an article has been bookmarked, blogged about, cited in Wikipedia and so on. These metrics can be considered altmetrics – alternative metrics of impact. (Appropriately enough, the term altmetrics was first proposed in a tweet [https:/twitter.com/asnpriem/status/25844968813].)" Heather Piwowar
Heather Piwowar is a postdoc at Duke University, studying the adoption and use of open research data. She is also a co-founder of ImpactStory (http://impactstory.org/), an open-source web tool that helps scholars track and report the broader impacts of their research. @researchremix