I am an ophthalmic tech so see a lot of this. As a general rule, the name brand doesn't mean a lot. Systane is a good brand and so is Refresh. If the drops aren't doing enough, try the gel drops. They are thicker but they will blur your vision (because it's a thicker substance). I love the gels, they feel so good.
They also make artificial tear ointments which are best used before bed because they are so thick. You might have to ask the pharmecist where they are because they aren't as common but they are over the counter. If you are having to use regular tears more than 4-6 times per day, you should switch the the preservatice free tears in the vials.
If you are still bothered, you should talk to your ophthalmologist (if you don't have one, look for a cornea specialist). There are several options they can do. Restasis is a medication but it takes a long time to take effect and they are expensive. They can do a dry eye test with paper strips called a shirmer test which will measure just how dry your eyes are. I would ask the doctor about the test, it only takes 5 minutes.
If they are really dry, they can put in punctal plugs which everyone described up above. If they work well, they can permanently close the holes.
Also, someone mentioned above taking fish oil supplements. I worked for a cornea specialist and he was a huge fan of the fish oil vitamins for dry eyes (to the point where I started taking it myself)
The tears won't cause macular degeneration. Genetics, age, and UV exposure will. I've never heard of any medications contributing to it it but couldn't say for sure.