Can you use filler on the inner upper eyelid?

Yes, filler can safely be injected in the upper eyelid hollows.  See manuscript I have published on this topic in the link below. Also see before/after photos.

You are correct that this technique has been described in the literature as an off-label method to correct mild amounts lid retraction in certain patients. It involves flipping the eyelid and placing the filler "transconjunctivally" (just underneath the thin layer of tissue lining the inner aspect of the lid) and just above the "tarsal plate" (the rigid framework of the lid). The filler basically acts as a weight, pushing the lid downward. The reported benefits of this technique are that it is reversible (hyaluronic acid filler can be dissolved), not permanent, and can be precisely placed by an experienced injector to achieve the desired lid height and contour. Since it is not permanent, however, the results don't last forever, and additional treatments are needed. The more permanent option to correct upper lid retraction involves different surgical procedures. Although the recovery from these procedures is a bit more involved, in the hands of a good eyelid surgeon, you should see good results, which are longer-lasting.The bottom line is that good results can be obtained via multiple approaches as long as you are being treated by the right surgeon.My advice would be to see an experienced oculoplastic surgeon well-versed in both of these treatment methods who will do a thorough exam and determine the safest option(s) for you. 

That being said, it is an unusual request to hear of someone wanting filler in the inner corner of their eyelid. What is the reason for the upper eyelid exposure? Did you previously have surgery? In general, we use filler to volumize and area that has lost volume or we wish to be fuller. If the exposure is from scar tissue or over resection of eyelid skin previously, you are best off with a surgical scar release and/or replacement with that which was lost (ie. Skin). Fat can certainly be use to fill regions, however, I would not recommend it for an eyelid as the area needs to be treated very delicately. Sometimes it can be difficult to control placement of very small aliquots of fat. Additionally, you don't normally have a lot of fat in your eyelids, so no reason to put more there. 

Small amounts of a hyaluronic acid dermal filler can carefully be placed in the upper eyelid area.A skilled injector should do this treatment to minimize treatment swelling, bruising and to insure proper placement.This may be considered an Off-Label treatment.