Clean your old eyeglasses with a piece of soft cloth after you have taken them off permanently. You should not just hand over the glasses to any charity. It is better to clean them properly before giving them away.
If you have managed to keep the original packaging of the glasses since you bought them, it will be great to hand them to a charity in that packaging. Or else, you can use a good leather pouch to put the glasses. You can also use a cloth bag.
You can find a charitable organization or an NGO in your country that collects old sunglasses and then makes arrangements for delivering them to the needy people in different countries. Make sure you choose a charity that specifically works for the cause of eyes care.
While delivering your old glasses to a charity of your choice, request for a receipt from them. This can help you get some compensation in taxes. You might also request the charity to make sure that they deliver the glasses to someone in need. Some charitable organizations just collect old stuff and then sell them. This cannot help delivery of the glasses to the needy, and they might end up being wasted at a charity shop.
Donate To Someone You Know
It is possible nowadays that you know someone through your friends or any other way in need of charitable products. You might know of someone from your relatives who can make an effective use of these glasses. You will have to search for such a person.