What is a double eyelid and what is a single eyelid
A double eyelid is an upper eyelid with a visible crease between the lash line and the brow. The crease forms where fibres from the levator muscle, the muscle that lifts the lid, pass through the orbicularis muscle and attach to the skin. When the eye opens, the levator pulls that attachment inwards and the skin above it folds over.
A monolid has no such attachment, or one that sits so low that the fold is hidden, so the eyelid skin drapes smoothly from the brow to the lashes. Monolids are not a defect and need no treatment, being one of several normal patterns described below. The full guide to this concern is at Double eyelids, and the options for creating or restoring a crease are compared at Double eyelid surgery in Singapore.
Monolids vs double eyelids, eyes with no crease
A monolid, also called a single eyelid, has no crease at all when the eye is open. Studies of East Asian populations put the proportion at roughly 40 to 50 per cent, with wide variation between individuals and families. Monolids tend to have a fuller upper lid because the orbital fat sits lower and the skin is thicker, and the lashes often point downwards because the lid skin rests on them.
Features that commonly accompany a monolid are a lower lash line that is partly hidden when the eye is open, a flatter brow bone, and an epicanthal fold, the web of skin at the inner corner that covers part of the tear duct. None of these need treatment, but they decide which surgical method is likely to hold.
Hidden double eyelid or inner double eyelid
A hidden double eyelid, sometimes called an inner double or a low crease, is a crease that exists but is covered by the skin above it when the eye is open. Looking down or closing the eye reveals it. Many people with an inner double eyelid describe their eyes as “sometimes double, sometimes single”, because the crease shows when the lids are rested and disappears when they are puffy or tired.
This pattern is the one most likely to change through life. The attachment is weak and the fold sits only 1 to 3 mm from the lash line, so a small amount of extra skin or fat is enough to hide it. People with this type who want a defined fold usually need the least surgery, because the attachment already exists and only needs raising or reinforcing.
Tapered double eyelid
A tapered fold, also called a nasally tapered or “in-fold” crease, runs parallel to the lash line on the outer two-thirds of the eye and then narrows and merges with the epicanthal fold at the inner corner. It is the commonest natural double eyelid pattern in East Asian eyes and the one most surgeons produce by default because it sits within the existing anatomy.
A tapered fold looks softer and more rounded than a parallel one. It suits an eye with a visible epicanthal fold, because the crease disappears into that fold rather than ending against it.
Parallel double eyelid
A parallel fold, also called an “out-fold”, keeps the same distance from the lash line along its full length and stays visible at the inner corner. It is the natural pattern in most European eyes and in a minority of East Asian eyes, usually those without a strong epicanthal fold.
Creating a parallel fold on an eye that has an epicanthal fold usually requires an epicanthoplasty, a second small procedure that releases the inner-corner web. Without it, the crease is forced to end in a sharp triangle at the inner corner, which is the main reason some surgical results look unnatural. The fold shape is therefore a design choice to settle before surgery, not after.
Double eyelid fold height and crease width
Fold height is the distance from the lash line to the crease when the eye is open, measured in millimetres. Low folds of 3 to 5 mm read as subtle, 5 to 7 mm is the range most Asian patients and surgeons describe as natural, and above 8 mm the fold starts to look surgical on an East Asian face. Above 10 mm it can look like a European lid transplanted onto an Asian one.
Crease width is a related but different measurement, the amount of skin that shows between lash line and fold with the eye open. Two people with the same fold height can show different widths depending on how far the brow sits over the lid. Fold height alone is therefore a poor way to choose a target, and a surgeon should measure both with the patient looking straight ahead.
Hooded eyes vs double eyelid, hooding is not the same as no crease
Hooded eyes have a crease, but the skin above it hangs down and covers it, often reaching the lashes. The problem is excess skin, sometimes with descended brow fat, rather than a missing attachment. Hooding is mostly age-related and becomes common after 45, but some people are born with heavy lids.
The distinction matters because a crease-forming operation does nothing for hooding, since the extra skin simply folds over the new crease. Hooded lids need an upper blepharoplasty that removes skin, which is a different operation with different downtime and a visible scar in the crease. The two are often combined in older patients. Hooding that has reached the point of blocking the upper field of vision is a medical rather than a cosmetic problem, and in Singapore may be MediSave-claimable after a visual field test.
Asymmetric double eyelids
One eye double and one single, or two creases at different heights, is common and often inherited. Roughly a third of people have measurable asymmetry. Causes include a weaker attachment on one side, an uneven epicanthal fold, a slight difference in brow position, or early ptosis on one side.
Asymmetry that appears in adulthood, especially if the lower-looking eye also seems smaller or sleepier, points to ptosis rather than to a crease difference. That needs assessment of the levator muscle before any cosmetic surgery, because tightening the crease on a ptotic lid makes the droop more obvious.
Why double eyelids disappear with age or ptosis
A crease that was present in youth and fades in the thirties or forties is usually loss of the levator-to-skin attachment. The fibres stretch, the lid skin thins and loosens, and fat descends over the crease. Contact lens wear for many years, eye rubbing from allergies and heavy eyelid make-up removal all accelerate this.
Ptosis is different. In ptosis the levator muscle or its tendon has stretched or detached from the tarsal plate, the stiff cartilage inside the lid, so the whole lid sits lower and the eye looks smaller. The crease often rises to an unnaturally high position or doubles up. The signs are a lid margin that covers more than 2 mm of the coloured iris when looking straight ahead, a raised eyebrow on the affected side from compensating, and a tired look that does not improve with sleep. Ptosis needs a ptosis correction, which is covered on Double eyelid surgery in Singapore, not a suture crease.
How to tell which double eyelid type you have
- Face a mirror in daylight and look straight ahead. If no crease is visible, go to step 2. If a crease is visible, go to step 3.
- Close the eye gently and look down. A faint line that appears 1 to 3 mm above the lashes is a hidden or inner double eyelid. No line means a monolid.
- Follow the crease towards the nose. If it narrows and runs into the inner-corner skin, it is tapered. If it stays at the same height and remains visible at the inner corner, it is parallel.
- Lift the brow with a finger and note whether the crease becomes clearer. If a lot of skin lifts away and the crease was hidden under it, the main issue is hooding rather than fold type.
- With the brow held still, check whether the lid edge covers more of the iris on one side than the other. If it does, ptosis should be assessed medically before any cosmetic procedure is decided.
What makes a double eyelid less visible
Puffiness from salt, alcohol, crying or poor sleep thickens the lid and hides a low crease. Allergies and eye rubbing stretch the skin. Weight gain increases lid fat. Years of eyelid tape or glue can leave the skin lax, although the reported cases are few. Ageing of the brow pushes skin down over the fold. None of these change the underlying type, but they explain why an inner double eyelid can look like a monolid on some days.
Which treatment suits which eyelid type
| Eyelid type | What is usually recommended | Read more |
|---|---|---|
| Monolid, thin skin, little fat | Suture (DST) method | Double eyelid surgery in Singapore |
| Monolid, thick skin or heavy fat | Partial or full incision with fat removal | Double eyelid surgery in Singapore |
| Hidden or inner double eyelid | Suture method to raise and fix the crease | Double eyelid surgery in Singapore |
| Tapered fold wanting a parallel fold | Incision with epicanthoplasty | Double eyelid surgery in Singapore |
| Hooded lids with excess skin | Upper blepharoplasty (skin excision) | Double eyelid surgery in Singapore |
| Crease lost with a droopy lid | Ptosis correction, then crease | Double eyelid surgery in Singapore |
| Any type, not ready for surgery | Tape or glue for occasional use | Double eyelid surgery in Singapore |
Related concerns that often appear with eyelid questions are covered at Eye bags and Sunken-looking eyes.
Frequently asked questions
What percentage of Asians have monolids?
Published surveys of East Asian populations report that between 40 and 50 per cent of adults have no visible upper-eyelid crease. The figure varies by region and family, and many of the remainder have a low or hidden crease rather than a prominent one.
Can a monolid become a double eyelid naturally?
Yes, in some people. The levator attachment can strengthen during adolescence, and loss of lid fat with age sometimes reveals a crease that was hidden. The reverse, a crease that disappears, is more common after 35.
What is the most natural double eyelid height?
For East Asian eyes, 5 to 7 mm above the lash line with a tapered or gently parallel shape is the range most patients and surgeons describe as natural. Above 8 mm is where results start to look operated.
Is a hidden double eyelid the same as a monolid?
No. A hidden or inner double eyelid has a crease that shows when the eye looks down or closes, whereas a monolid has none. The distinction matters because a hidden crease can usually be raised with the suture method alone.
Why does my double eyelid disappear when I am tired?
Fluid and fat swelling thicken the lid and cover a low crease. This is normal for an inner double eyelid. A crease that is gone most of the time, together with a lid that sits lower on the iris, suggests ptosis and should be checked.
General information, not medical advice. A registered medical practitioner should be consulted before any treatment. Dark Eye Circles Singapore does not sell treatments and is not a clinic.
Sources and price references (checked 5 October 2026)
- Jeong S, et al. The Asian upper eyelid: an anatomical study with comparison to the Caucasian eyelid. Arch Ophthalmol. 1999;117(7):907-912. doi:10.1001/archopht.117.7.907 (PMID 10408455) — Cadaver study; levator-septum fusion and fat position explain crease presence and height https://doi.org/10.1001/archopht.117.7.907
- Saonanon P. Update on Asian eyelid anatomy and clinical relevance. Curr Opin Ophthalmol. 2014;25(5):436-442. doi:10.1097/ICU.0000000000000075 (PMID 24852200) — Narrative review; crease types, epicanthus, fat and skin thickness https://doi.org/10.1097/ICU.0000000000000075
- Wang Q, et al. DNA-based eyelid trait prediction in Chinese Han population. Int J Legal Med. 2021;135(5):1743-1752. doi:10.1007/s00414-021-02570-7 (PMID 33969445) — Chinese Han cohort; single vs double eyelid frequency and heritability https://doi.org/10.1007/s00414-021-02570-7
- Lew DH, et al. Surgical correction of multiple upper eyelid folds in East Asians. Plast Reconstr Surg. 2011;127(3):1323-1331. doi:10.1097/PRS.0b013e318205f32b (PMID 21364433) — Case series; multiple-fold anatomy and correction https://doi.org/10.1097/PRS.0b013e318205f32b
- Wang S, et al. The Medial Canthus Fibrous Band's Impact on Epicanthal Fold Severity and Classification in Asians: Implications for Epicanthoplasty. Aesthet Surg J. 2024;44(6):580-587. doi:10.1093/asj/sjae004 (PMID 38198214) — Anatomical/clinical study; epicanthal fold grading for surgical planning https://doi.org/10.1093/asj/sjae004
- Fakhro A, et al. The Evolution of Looks and Expectations of Asian Eyelid and Eye Appearance. Semin Plast Surg. 2015;29(3):135-144. doi:10.1055/s-0035-1556847 (PMID 26306080, PMC4536060) — Review; cultural context and crease preferences, not outcome data https://doi.org/10.1055/s-0035-1556847