Two things are happening here. One, the hormones in birth control pills can actually alter your vision. Two, you are experienceing dry eye which could be effected by the pills. Simple solution for the dry eye... Flax Seed Oil. You can take it in a liquid form (add it to smooties, etc.), buy bread, like Orowheat, that contains flax, or you can buy flax seed pills. If you take the pills, make sure they are organic. Best thing is to get them from your whole foods store. Take one in the morning and one at night. I promise you will notice a huge difference within a day or two. The key is the Omega 3 Fatty acids which lubricate your eyes, joints, and skin from the inside out. This is a key element for your health.
I had Lasik surgery on my eyes a few years back. WONDERFUL experience except for the dry eye I experienced after, which became painful. In my quest to figure out a way away from eye drops forever, I discovered the flax oil and it worked!