Each of these needs a different approach, and each has many pricey products that you can go out and buy in your local chemists or pharmacy which work well – but here are some simple and everyday solutions :
For the lens : The most important thing is to be gentle with any chemicals/detergents or rubbing agents. If the glass is just dirty, and not covered in grease from when you adjusted your glasses with the hand that just managed the ingestion of your cheeseburger – then the classic slow but steady breath onto the lens followed swiftly by a gentle massage with a good quality linen or cotton cloth still works well. When you have transferred remnants of your lunch to the lens however, some chemical introduction coupled with temperature takes it to the next level.
For normal glass or plastic lenses, a quick dunk in a pool of warm water with a couple of drops of washing detergent will usually do the trick to break through the grease. Of course if warm water isn’t available, a quick spray with a commercial/domestic window cleaner also does well. Be Careful however if you have an anti-reflection coating on your lenses – which is common on glasses that have been prescribed for night driving – as the surface of these lenses have been treated and washing up liquid or detergents will often smudge the lens even more and just make the situation worse. For this situation, you are better off with an optical spray and a nice clean cloth. The tip here is that it doesn’t have to be a glasses spray from the opticians – any optical spray (for cameras for example) will work just fine.
For the nosepads : The surface of the nosepads are generally quite resistant to dirt and natural oils. They are usually made form a type of plastic or acetate -and so are not prone to reactions with the skin. Dirt can easily get lodged however between the nosepads and their mounts or the frame itself – so a warm soak for a couple of hours overnight will soften the residue – which can then be gently brushed away with an old soft bristle brush or toothbrush.
For the frame : Many frame materials can form a greenish hue over time due to reactions with the skins natural acidity – and in the worst cases can actually corrode. The best resolution to this is to not let the glasses touch the face in the first place. If you can feel the frame touching the skin, then gently adjust the nosepads inwards to raise the glasses from the face. Once the green is on the frame, it is almost impossible to remove I’m afraid.
Finally – the best way to keep your glasses or spectacles in tip top condition is to regularly rinse them in warm water, shake off most of the water and then dry gently. If you can stop dirt from building up in the first place, things don’t get to a crisis point !