If you use your laptop for long hours does it have any effects on eye sight/vision?

Not really: There is no specific danger with using laptops or computer monitors. With any prolonged near work, whether it be computer work or reading, the eyes can be fatigued from prolonged focusing. Taking intermittent breaks and varying the distance of the near work can help avoid eye strain. Sometimes low powered reading glasses might be needed, but not usually until a person is in their 40's.

Yes: The eye surface can become dry making the eyes scratchy, red, blurry, and tear. Use artificial tears and/or take breaks. It may also cause accommodative strain. This would be a tight or tension type pain/headache in the forehead. You may also experience difficulty readjusting for distance vision for a short time. No permanent harm though.