If your eyes seem strained at the end of a long day or after staring at your computer screen too long, don't be alarmed. During pregnancy your body is retaining more water (which explains the swollen ankles and belly bloat you may have), and this fluid retention can also cause the outer layer of your eyes to thicken slightly, resulting in blurred vision. Some women notice vision changes as early as 10 weeks into pregnancy, and the blurriness can last as long as six weeks postpartum. Although most vision changes are normal, doctors agree that you should have your eyes examined to confirm that the blurriness is pregnancy-related and not caused by some vision impairment. There's no need to change your prescription, since your vision will eventually recover. This fluid retention can also make wearing contact lenses uncomfortable, so you may want to stick to your favorite frames if your lenses are bothering you.
However, if the blurriness comes on suddenly, or you see spots in your eyes, let your doctor know right away. These could be signs of uncontrolled diabetes or preeclampsia (a form of pregnancy high blood pressure).