Who is at risk for open-angle glaucoma?

See other answer. Technically everyone, and as you age the risk gets higher. But family history is a factor, certain ethnicities have increased prevalence, some genetic or environmental factors can make a difference as well. Having an eye exam will find any other risk factors.
Risk factors are... Family/ethnicity are important. Those at highest risk for open-angle glaucoma have a sibling with glaucoma; or a parent. African-americans and hispanics are at higher risk than caucasians. Asians have a higher risk for angle-closure disease (e.g., chinese); others are at for risk low-pressure glaucoma (japanese.) other risks include a serious eye injury, or long exposure to Prednisone therapy.
Many Factors. Many studies have examined this. Risk factors are elevated intraocular pressure, thin corneas, suspicious appearing optic nerves and positive family history. People of african descent may be more likely than others to develop glaucoma. The older you are, the greater the risk. The best way to determine your risk is to have a complete eye examination.
Also hispanics. In addition to the excellent answer given there is also an apparent increased incidence in hispanics.