This happens when they touch an area of themselves that has a herpes sore, and then they rub their eyes. Consistent condom use will greatly decrease the likelihood of spreading herpes but there is no such thing as no risk. Sexual contact should be completely avoided when a person is having an outbreak of the sores. Hand washing after using the toilet or touching a sore will prevent infection in the eyes. If you are infected with herpes, it is your job to do your best to prevent others from getting herpes from you.
Most people consider it their duty to warn people about their herpes infection before having sex.