I heard about double eye lid cosmetic surgery. Will this affect my eye health?

No. This is a common cosmetic procedure performed on asian eyes to create an extra horizontal lid crease and make the eye more western looking in appearance. If done by an experienced surgeon, it should not affect your eye health.
Should not. If are a good candidate for this surgery and surgery goes well and you follow all directions after surgery, your "eye health" should remain the same. However, no surgery is without risks. Talk to your surgeon.
Probably not! Since loose skin is removed and your eyes are more open and refreshed in appearance, there can be more tear evaporation, dry or irritated eyes, and other potential issues. But well-performed blepharoplasty (2 or 4 lids) by an abps-certified plastic surgeon after proper evaluation and careful measurements can yield wonderful results and no problems with your eye health at all--you just look better!