There are three types of ptosis: mild, moderate and severe. Moderate to severe ptosis affects vision and is easily detected and corrected. Mild ptosis, on the other hand, does not affect vision and often goes unnoticed by the patient. We occasionally encounter mild ptosis prior to blepharoplasty, and most patients come in with a request for blepharoplasty, which is only diagnosed after careful examination (including an upper eyelid muscle strength measurement) and thorough communication with the patient. This is often overlooked by inexperienced surgeons, resulting in a missed diagnosis. If the surgery is performed as a conventional blepharoplasty, it is difficult to create a smooth blepharoplasty line, whether it is buried or incised, resulting in an unnatural shape. The surgeon has his hands full during surgery or over-trims the orbicularis oculi at the inner and outer canthus. The focus is on diagnosis. As long as the diagnosis of single lid with mild ptosis can be confirmed, treatment is not a problem. This ptosis is often masked by a single lid and the levator muscle strength is mostly above 8 mm, which can be corrected with an upper lid lift folding procedure. Patients and young plastic surgeons are reminded that it is important to carefully examine and fully communicate before blepharoplasty to see if there is unequal size between the two eyes, and thus find out if the corneal exposure is the same on both sides and confirm the diagnosis of mild ptosis.