I'm sure your dermatologist is doing a great job. When it comes to the eyelids, the lower eyelid is an extremely common site for basas cell carcinoma (possible the number 1 or 2 most common site.) I see them all the time. Basically, you need an ophthalmologist to look at the lesion with the slit lamp and if it looks suspicious, he can perform a biopsy and excision if needed. If it is a significant lesion - you may need a oculo-plastic surgeon. Dermatologist don't usually work on the eyelids. I think it's important to get it checked out by an ophthalmologist.
Thank you for the information it helps me make the decision I have been putting off.