Eyelid Ptosis Explained: Causes, Diagnosis, and Treatment

Eyelid ptosis (눈꺼풀 하수, nunkkeoppul hasu — literally “eyelid drooping”) is the medical term for an upper eyelid that sits lower than its normal position due to weakness or dysfunction of the levator palpebrae superioris — the primary muscle responsible for lifting the eyelid. In mild cases, ptosis looks like persistent tiredness or asymmetry between the two eyes. In moderate-to-severe cases, the drooping lid partially covers the pupil and restricts vision.

Three structural causes account for most cases: congenital ptosis (the levator muscle does not develop fully before birth, more prevalent in East Asian patients), aponeurotic ptosis (the fibrous tendon connecting the levator muscle to the eyelid — the levator aponeurosis — gradually stretches or detaches, typically from ageing or prolonged contact lens wear), and neurogenic ptosis (disruption to the nerve controlling the levator — rare and requiring separate neurological evaluation before any surgical planning).

How Ptosis Is Diagnosed at Korean Clinics

A structured consultation at a Korean plastic surgery clinic measures two values central to ptosis diagnosis.

Marginal reflex distance (MRD) is the distance in millimetres from the centre of the pupil’s light reflex to the upper lid margin when the patient looks straight ahead in natural light. A normal MRD sits between 3.5mm and 4.5mm. An MRD below 3mm is consistent with ptosis; below 2mm indicates clinically significant ptosis with potential visual field involvement.¹

Levator function measures how far the upper lid travels from full downward gaze to full upward gaze while the surgeon holds the brow still to prevent brow-raising compensation. Excursion above 10mm indicates good levator function — consistent with aponeurotic ptosis and a favourable prognosis for levator advancement surgery. Excursion below 4mm indicates poor levator function — consistent with congenital ptosis and pointing toward a frontalis sling procedure.¹

Brow position is assessed alongside lid measurements. Many patients with mild-to-moderate ptosis unconsciously raise their brows to widen the eye opening, which masks the true severity of lid drooping during a casual examination. Surgeons at clinics registered with 대한성형외과학회 (Daehan Seonghyeong Oegwa Haghoe — the Korean Society of Plastic and Reconstructive Surgeons, KSPRS) are trained to perform this full assessment protocol as part of routine eyelid consultations.¹

Ptosis and Double Eyelid Surgery: Why Order Matters

쌍꺼풀 수술 (ssangkkeopul susul — double eyelid surgery) creates a visible upper eyelid crease by connecting the skin to the underlying levator aponeurosis or tarsus (the firm cartilage-like plate inside the eyelid). The crease becomes visible because the lid skin folds at the attachment point when the eye opens.

The problem with uncorrected ptosis is mechanical: if the levator is weak or the aponeurosis is detached, the lid does not open to its full height. The extra skin above the lid margin has nowhere to fold upward — instead, it folds downward over the crease and buries it. The result is a crease that is shallow, asymmetric, or invisible within months of surgery. The eye continues to look heavy despite the operative intervention.¹

Correcting ptosis at the same time as double eyelid surgery eliminates this problem. Because full-incision double eyelid surgery exposes the levator aponeurosis through the upper eyelid incision, the surgeon can advance and re-attach the aponeurosis in the same operative field without additional incisions or surgical time. The crease is then formed at the corrected lid height, producing a result that reflects the actual post-correction anatomy rather than the pre-correction droop.

A surgeon who does not assess levator function before proceeding with double eyelid surgery is operating without complete anatomical information — the crease design and height will be based on incorrect assumptions about how the lid will behave after healing.¹

Ptosis Correction Techniques in Korea

Levator advancement (aponeurotic ptosis): The upper eyelid is opened through the planned double eyelid incision line. The levator aponeurosis — which has stretched or partially detached from the tarsus — is identified, advanced downward, and sutured back to the tarsal plate at a position that raises the lid margin to the target MRD. The amount of advancement is calibrated intraoperatively: most surgeons perform this procedure under local anaesthesia so the patient can open their eyes on request during the procedure, allowing the surgeon to judge lid height and symmetry in real time. Recovery overlaps with double eyelid surgery recovery — swelling, bruising, and temporary lid stiffness for two to four weeks.¹

Frontalis sling (congenital ptosis with poor levator function): When levator excursion is below 4mm, the levator cannot reliably hold the correction. A sling — made from autologous fascia (tissue taken from the patient’s own thigh) or a synthetic material — is anchored to the frontalis muscle in the brow and looped under the lid, transferring the brow muscle’s lifting force to the upper eyelid. This allows the patient to open the eye by raising the brow. The frontalis sling is a more complex reconstruction with a longer recovery and is reserved for cases where levator advancement would be insufficient.¹

Self-Assessment: Signs You May Have Ptosis

The following signs suggest ptosis may be present. None replaces a clinical measurement, but each is worth noting at consultation.

• One eye appears smaller or more hooded than the other in photographs taken from straight ahead — asymmetric lid height is one of the most consistent visible signs.
• You habitually raise your eyebrows when trying to look alert or when photographs are taken — this is the compensatory brow raise masking the lid droop.
• Previous double eyelid surgery produced a shallow or disappearing crease — especially if the crease was visible immediately after surgery but faded within months.
• Eye fatigue or forehead headaches without a refractive (glasses) explanation — both result from sustained brow muscle contraction used to compensate for lid drooping.
• Head tilting back to improve the line of sight, particularly when reading or using screens.
• Asymmetric eye opening in video calls or photographs — lid asymmetry is often more obvious in still images than in the mirror, where compensatory movement is automatic.

If three or more of these apply, raise them at consultation and request that levator function be measured formally. Do not assume a surgeon will perform the assessment unprompted — request it by name.¹

Sources

¹ Korean Society of Plastic and Reconstructive Surgeons — Board Certification Registry. Board certification requirements, public registry, and legal requirements for plastic surgery practice in Korea. KSPRS, 2024. https://www.plasticsurgery.or.kr/