Since it seemed like several people in this thread mentioned issues with dry eyes, I figure I'd throw some options out there. I'm a 3rd year medical student, and I just spent a month on an ophthalmology rotation. I also live in Nevada which is the dry eye capital of the world so I've seen pretty severe cases and have probably seen most of the available treatment options.
If you've had LASIK, PRK, or LASEK in the past year, I would stick with the preservative free tears that come in the single use disposable vials. If they aren't working for you I'd consult with the doctor who performed your surgery before adding any other type of over the counter tears.
There are a lot of over the counter tears that you can use which most patients find solve their problems. Optive is the newest and seems to work well from the patients I've talked to. Systane is also a popular one. Everybody is slightly different and it's good to try different brands to see what works for you. Most people find that using them 3-4 times a day is enough, some may need more applications and some may need less. They can be used as many times as you like, but if you find yourself using them more than 5 times a day it can become tedious, and that's when most patients try to find an alternative. If you want a more longer lasting drop, there's Refresh Liquigel that is more thick and viscous. It lasts longer but it also can blur your vision for a few minutes after you use it. It's probably best to use it before you go to bed at night or right when you wake up. I would stay away from Visine or Murine as they are only useful for cosmetic purposes to decrease redness. They work by constricting the vessels in your eye and if used too often can cause a rebound effect by making your eyes even worse than you started.
If OTC tears aren't working or you find them too inconvenient, another solution is punctal plugs. Your tears are produced by the lacrimal gland and drain through the superior and inferior canaliculus down to the nasolacrimal duct into your nose. A silicone plug can be inserted into the cnnaliculi to prevent drainage and keep your tears in your eye. It's a painless procedure and literally takes less than a minute to peform. The plugs can always be removed if you find them irritating, and they make temporary plugs made out of collagen that only last a few days before they dissolve. Some patients like to try these as a test run to see how well it works or to see if it causes them discomfort.
There is only one prescription treatment that actually both increases tear production and improves the quality or tears called Restasis. They've started running TV advertisements that you may have seen recently. Restasis is a topical Cyclosporine drop that needs to be administered twice a day. Most people use it when the wake up and before they go to bed. It's safe to use an OTC topical drop like Optive or Systane during the day in addition to Restasis. I believe about 85% of people find it improves their dry eye condition. The downsides are that it takes a long time for it to work, sometimes it stings for 10-15 seconds, and it's also somewhat expensive. It comes in single use disposable droppers but if you save them, they can usually last for 2 days or 4 applications. Some people are apprehensive about using it because Cyclosporine was originally used as an immunosuppressant agent for transplant patients and if you google Cyclosporine, you find that it can have some severe systemic side effects. With Restasis you don't have to worry about those because you're using it topically and you also get extremely small amounts of it in comparison to the quantity you'd have to take to experience side effects.
Unless you have extremely severe dry eye syndrome, you should be able to get relief with any one or combination of solutions I've mentioned above. If you're using tears, plugs, and Restasis without any success, the last option I know of is an OTC oral pill called BioTears. You have to order it directly from the website of the manufacturer, Biosyntrx. Your tears have a lipid, aqueous, and mucus component and BioTears basically is a mix of fatty acids and other miscellaneous ingredients that in theory should help with tear quality. It's kind of a long shot and any improvement is minimal at best, but it doesn't contain anything that could cause harm and I've met some patients that claimed it helped. I Caps is multivitamin that works along the same principle, just with a different formulation.
That basically covers most of what's out there. As I mentioned before, I'm just a student and these were what I saw being used at the practice where I worked. Your eye doctor may have a different strategy for treatment. I would highly recommend talking with your ophthalmologist about if your dry eyes if OTC tears aren't cutting it. You would need to see him/her anyways if you wanted plugs or a prescription for Restasis. Hope that helps and if there are further questions for anything, feel free to ask.