Can ptosis surgery in one eye have an opposite effect of Herring’s law and lift lid on uncorrected eye?

The other surgeons in this section have given an excellent explanation of what Herring's law is and how a droopy eyelid may not look droopy until after the opposite droopy side is operated upon (and corrected). They have also explained the logic behind one-sided or two-sided surgery very well.
The common questions we have come across regarding one-sided ptosis over the years are as follows:
1. If I have a droopy eyelid on one side, should I have surgery on one side or both sides?2. If I have surgery on one side because the Herring's test did not show my "good" eyelid coming down, is there still a chance that the lid would become lower after one-sided surgery?3. What is the best option for me?4. When should one-sided droop of an eyelid be repaired? Should I wait until both sides droop?
As we get these questions frequently, it will be helpful to others to go over our experience and results.
Q1. If I have a droopy eyelid on one side, should I have surgery on one side or both sides?
A1. When the Herring's is positive, it makes sense to operate upon both upper eyelids at the same time. It should be remembered that when the Herring's test is done (by lifting the droopy lid and watching the "normal" eyelid for drooping), the relaxation of the "normal" side may not always be obvious or dramatic. Subtle changes can be easily missed. So a careful, and, if necessary, a repeat examination is vital to help make a decision.
Q2. If I have surgery on one side because the Herring's test did not show my "good" eyelid coming down, is there still a chance that the lid would become lower after one-sided surgery?
A2. Absolutely. The preoperative Herring's law test is usually predictive, but there can be a mild ptosis on the unaffected side which can become manifest after unilateral surgery. Swelling, bruising, etc after surgery will make the operated eyelid look persistently droopy for some days (even weeks) and therefore, it is important to give the body a chance to heal and the neurological responses (Herring's in other words) to manifest themselves. We will generally not make any judgement about the final lid height for at least two months after surgery, sometimes longer.
Q3. What is the best option for me?
A3. How many different shades of grey are there? Horses for courses. One should not just assess the eyelids. The relationship of the eyelids to the brows (depending upon racial characteristics, sun exposure, contact lens wear, age, etc) has to be considered. Asymmetry of the face (we all have asymmetric faces) becomes slowly-but-surely more apparent as we age and this applies to the periorbital area and eyelids as well. People forget to look at the position of the lower eyelids when addressing a droopy eyelid or eyelids. We will all have one lower lid a little different (lower, fuller, etc) when compared to the other. So, after an assessment of all these factors, and with the help of a full-face photograph, options can be discussed. I am not making it more difficult than it is: it is just important for the surgeon to consider all these factors as in my experience, everyone cares about how they look and how they turn out after surgery.
Q4. When should one-sided droop of an eyelid be repaired? Should I wait until both sides droop?
A4. This is simple. If a slightly droopy eyelid does not bother you functionally or cosmetically, leave it well alone. Have a look at all your family and friends: they all have one eyelid a tad lower than the other. And nobody, even in this age of Insta-bloody-gram, looks at us as closely as one might think. If it does bother you, then consider the details outlined in answer number 3 above.
Finally, and I know most of the surgeons who have replied here would be examples of the types of surgeons you should be seeking: the surgeon needs to pay just as much attention after surgery and watch you clinically and photographically and do what is right if any "adjustments" need to be made. Plastic surgery is an art, not a pure science and adjustments should be considered the norm and aim to give us better results.
I shall add examples of patients who underwent one-sided or two-sided surgery for you to review and understand the above.
bckp

With Herring's law, when one ptotic lid is elevated, the "normal" lid will then fall.   The non-operated lid will not elevate on its' own. 

Your question is a good but challenging one! Ptosis ("toe-sis") is a drooping of the eyelid due to a weakness of the eyelid muscle. Ptosis surgery is very technical and requires great precision to have a natural, beautiful outcome.  Few surgeons are masters at this condition. Even in the best hands this surgery can be quite tough to achieve symmetry. You need an in-person consultation with a board-certified, fellowship-trained Oculofacial Plastic Surgeon with extensive experience in ptosis repair and eyelid surgery. Only then can the surgeon determine if it would be best to operate on one or both eyelids. Hering's law (one r) can only be determined in person with a proper clinical examination. Many patients travel great distances to see me for this sort of expertise. You must avoid any doctors that perform ptosis or eyelid surgery part time, they cannot help you. Unless ptosis is extremely severe it is not a medically covered procedure, and rarely is this covered in my practice unless the patients are very elderly -- it is considered cosmetic plastic surgery by insurance companies who set strict guidelines. Blepharoplasty (removing excess skin from the eyelid) is often performed at the same time as Ptosis repair. Please look at my before and after gallery here to see the results i strive to achieve. Best of luck to you.
Damon B. Chandler, MD
Harvard-Penn Trained Oculofacial Plastic Surgeon

Likely the effect of ptosis repair might in fact cause more obvious drooping of the opposite eye .  That is the reason that bilateral ptosis repair is done even when only one lid appears to be ptotic

By definition Herring’s law is that, when the ptotic eyelid is lifted the other one that was normal drops down and create ptosis. So there is no such thing as fixing ptosis on one side and a ptosis of the other side would  correct itself !

When an eyelid is droopy your brain notices the fact that it is drooping and works extra hard to lift the droopy eyelid.  However when that happens the opposite eye is often lifted as well.  After ptosis surgery for the droopy eyelid your brain can stop working so hard to lift the previously droopy upper eyelid.  However that "relaxation" can cause the opposite eye to sit a little lower as well.  That is Herring's law.  The opposite effect does not happen.