Miracle Glue will repair
a lot of sunglasses but not all. Some are made of particular
types of plastics that won't glue (polypropylene/polyethylene).
Usually, the higher end glasses are made of a higher quality plastic
and will bond better. Also, plastics are definitely a different
kettle of fish and some just take longer to bond. Where Miracle
Glue will bond most things in several seconds some plastics will take
a few minutes but will then bond well.