Cheap sunglasses do not block 100% of harmful UV rays and are therefore not recommended. More info in this Sunglasses Article
If you are allergic to metal frames, consider these 3 alternatives:
1. Plastic frame
2. Titanium frame
3. Apply clear nail polish to the temples of your metal frame.
Unlike bifocal and trifocal glasses, there are no lines in progressives lenses.
Bifocal and trifocal glasses have lines running across the lens. Therefore, they are not the best options if you value aesthetics.
Bifocal lenses are not recommended when using a computer, because no part of the lens is allowing you to see intermediate distance.