The eyes‘ adaptation to darkness is a long process which can take up to 30 minutes. However, the mesopic vision test of the Binoptometer® 4P is performed under mesopic light, i.e. twilight conditions, so partial dark adaptation is sufficient. Usually this is achieved within 5 minutes. Most young people, and others with very good contrast vision, are able to see the optotypes of the mesopic vision test after only one minute.