When buying a sunglasses case, you must first determine the primary purpose of the case. If you are simply looking for one in which you can store your sunglasses and protect their lenses from being scratched, a simple pocket-style case may be all that you need.
A pocket-style case is soft and typically made out of a stiff cloth. This type is easy to use because one end is typically open, making it convenient to remove and replace the sunglasses when not in use. The disadvantage of this type of sunglasses case, however, is that it provides very little protection against breakage.
If you need a case that will protect your sunglasses from becoming broken, you will need to purchase a hard sunglasses case. This type is typically hinged on one end and does not have an opening. Rather, you will need to flip the top portion up in order to retrieve your sunglasses. The hard shell protects your sunglasses from becoming broken, even if you accidentally sit on the case or drop it.
If you are going to purchase a hard-shell sunglasses case, it is important to be sure your sunglasses fit inside properly. If the case is too large, your sunglasses will rattle around inside the case and may still become damaged. Similarly, one that's too small can cause your sunglasses to become smashed when shutting the case.
Ideally, your case should be designed specifically for the shape and size of your sunglasses. Typically, higher-end quality sunglasses come with their own case that is included with the price of purchase. If one is not automatically included with the purchase of a new pair of sunglasses, it is worthwhile to inquire about one that will fit your specific style of sunglasses correctly.
You might also have the opportunity to select from a variety of colors and styles when shopping for a sunglasses case. The color and look of the one you purchase is entirely up to your own personal taste. Since others do not typically see the case on a regular basis, it shouldn’t be considered a part of your wardrobe and you don't need to worry about it clashing with your outfits. If this is a concern for you, however, you should purchase a case in a neutral color or purchase several different cases to suit a variety of outfits.