If you have the option for "blind and low vision" checked in OWA (Settings (gear icon), Mail, Light version, "Use the light version of Outlook"), you will automatically be logged into the light version of OWA.
If you have the option for "blind and low vision" checked in OWA (Settings (gear icon), Mail, Light version, "Use the light version of Outlook"), you will automatically be logged into the light version of OWA.