Anatomy of Asian Eyelids

Often, the skin of a single (fold) eyelid overhangs the eyelashes, thus making them appear shorter.  With double eyelid surgery, the excess skin overhanging the eyelash is either pushed into the new crease and/or removed so much more of the eyelashes can be seen, thus making them appear longer.  (Also, you will get less mascara smudges onto your eyelid skin since the skin will not be overhanging and pressing onto the eyelashes).

The amount of excess "skin" covering the eyelashes will depend on each person's anatomy, such as the quanitity of orbital fat, height of levator insertion onto overlying skin, etc.

That's an accurate observation.  The lashes do not always point down in patients with no double eyelid crease but they usually do.  Typically the lashes are elevated after anchoring technique Asian eyelid surgery via an incision technique.  Suture technique usually can create a crease but won't help lash position.This is genetic in as much as your anatomy is genetic.  It's also common to see lash ptosis (lashes pointing down) in the aging Asian eyelid or in cases where a patient has hyperelastic skin and soft tissues.  In these cases a patient may have a crease (that is usually poorly defined) but the anterior lamella (skin and orbiculares muscle) are loose the the lashes simply tilt downward.  Some of the angle of the lashes is also simply due to how your follicles are oriented so the surgeons ability to raise the lash angle can be limited in some cases.Hope that helpsChase Lay MD Asian eyelid surgery specialist

The Asian eyelid anatomy is different in few fronts but the major difference is absence of the skin attachment of the elevator mechanism which opens the eyes. There are also difference in the fat distribution that makes traditional eyelid surgery used in Caucasian eyelids different to Asian eyelids. These two major reasons combined can be part of the reason why the skin touches the eye lashes much much earlier and why their eyes (50%) seem much puffier in the morning because of edema/fluid. Very interesting anatomical differences. 
Wish you the best in your journey,
Dr Leo Kim, Specialist Plastic Surgeon in Sydney

You have made a good observation in that a person without double eyelids will have eyelashes that are aiming down. Also, not only would the eyelashes be aiming down, but if there is excess upper eyelid skin pushing down against the eyelashes, then it can also cause irritation to the cornea or irritation in sensation. However, by having a double eyelid surgery the eyelashes move up. One can think of the mechanism as a blanket that is just hanging versus somebody pushing that blanket in. Then what happens is that the bottom part of the blanket would elevate in height but still would want to touch the ground due to gravity. Just like this, when a crease is made on the eyelid, the eyelashes that are aiming down move up about 90 degrees. This is just a pure physical mechanism of a surface area that is being pushed in a concave manner. 

Your observation about the change in eyelid length has to do with their relative length. In before and after photos where the eyelashes appear to grow longer, the change is actually due to the fact that the extra skin pushing against and hiding a part of the eyelashes is either pulled upwards or removed during the course of double eyelid surgery. This allows you to see the full length of the eyelashes, and so they appear much longer.