Studies suggest that individuals who take often lutein have a lower risk of suffering cataracts and macular degeneration. So lutein is a safe supplement for general eye health, but you should check with your doctor how much lutein you should take for your eye health.
Yes. An appropriate dose of lutein is safe for general eye health. But if you already have a high intake of lutein in your diet, you may need a small amount of supplement or even you don't need them at all. Whether you should take lutein supplement for your eye health should consult your doctor.
Yes, it's absolutely safe, but don't expect too much from it unless you want to prevent/treat eye illnesses related to age (such as macular degeneration) or other retinal disorders .
If your problem is just eye-strain or you'd like to improve your eyesight, lutein will be useless.