No, as far as i know, the poor eyesight won't cause nausea. They have no connection. Poor vision usually caused by many vision problems or eye diseases. Vision problems such as myopia, presbyopia, and astigmatism are the reasons of poor vision. Besides, eye diseases such as cataracts or glaucoma can contribute to poor eyesight. But these problem have no connection to our stomach. So, i if you suffer nausea, you'd better consult a doctor.
Yep, it could be. And you may do something to improve this situation. Rest your eyes every an hour so that your eyes can get fresh air and will not get dehydrated. Your eyes can get tired easily, especially when you also suffer from nearsightedness or myopia. You really need to be very cautious whenever it is in relation with your eyes. If I didn' t remember wrong. I remember that eye strain usually comes along with a headache, blurry eyes and sickness. Maybe you just need more rest. Try doing some eye exercises when it is convinent for you.