Eyelid Terminology and Measurements
The palpebral fissure refers to the normal exposed area between upper and lower eyelids.
It is measured between the margin of the lower eyelid to the margin of the upper eyelid.
The normal palpebral fissure height (sometimes abbreviated PFH) is 8-11 mm. This is a key measurement that you need when assessing for ptosis (droopy eyelid).