Mesh part translucent

Hi,

I have a problem with translucent material : I have a gas mask with glasses, and I need to have the gas mask opaque and the glasses translucent. With no translucency ( masked material ), I have the correct gas mask but no translucency ( obviously ) :

With a translucent material, I got the correct glasses but the rest of the gas mask goes wrong :

My opacity mask is pure white for the gas mask with grey circles for the glasses.
What can I do to have the material working properly please ?

2 options:

Option 1: Use 2 materials on the character. 1 for the glass, one for all the other stuff.

Option 2: Use dithered opacity masking which is available in 4.12. It fakes translucency using a dither pattern which is then softened by temporal anti-aliasing. But option 1 is probably better in this case.

Thank you !