I think Bolle Ransom 115/25 can be the best choice for the men over 50, it's pretty cool, then make people look young and energetic.
Lot of celebrated brands provide classic sunglasses for men and women. Or you can buy some fashion sunglasses to make your uncle more fashionable.
There's a website, www.smartbuyglasses.co.uk, provide lots of designer sunglasses for discount. You can try to choose a pair sunglasses on that web.
As your uncle aged 50, declining vision and other eye diseases, such as presbyopia,cataract, glaucoma should take into account. So how about bifocal sunglasses that prescribed to people with presbyopia. bifocal sunglasses can both help to correct myopia hyperopia, astigmatism and protect eyes from harmful UV rays. Besides, there are also many other choices, and you can consider multifocal sunglasses that can ensure you enjoy seeing objects without any occurrence of image jump,which is also a perfect choice for senior citizens.
Both of bifocal and multifocal sunglasses have various colours and frames, and I think you can choose a suitable pair for your uncle.