Amongst East Asians (Chinese, Japanese and Korean), unequal double eyelids appear to be common in the normal population. Most cases are caused by poor attachment between the skin and the levator muscle in one of the eye. A study performed in Korea showed a prevalence of unequal double eyelids (in which one eye had double eyelid and the other without) is about 10.9%.
Song WC; Kim SJ et al. Asymmetry of the palpebral fissure and upper eyelid crease in Koreans. Journal of Plastic, Reconstructive & Aesthetic Surgery (2007); 60, 251-255
The eye without the double eyelid tends to appear smaller because of the eyelid skin hanging over the lid margin. This may sometimes be misdiagnosed as droopy eyelid. Treatment is to create a double eyelid similar in height to the eye with the double eyelid.
This patient was born with absent right upper skin crease. Over the year, she had been using glue and tape to create a double eyelid but find it time-consuming. She wanted a right double eyelid with minimal down time. I performed a DST (double suture twisting technique), the result appears satisfactory at one week follow-up without noticeable swelling.
Right double eyelid creation using DST.