Most of the roadie using glasses with TT helmet do it because of Oakley/other glasses company sponsorship. Any TT that is made with a visor will have worse aero drag without the visor. The Lazer Tardiz is one of the rare tt helmet that is designed for glasses that I can think of. Instead check for helmets that comes with multiple visors.In example the Kask bambino come with a mirrored visor and a clear one, other options are available seperate.