Monolids (Epicanthal Folds) Anatomy and Causes

“Monolids” is a colloquial way to describe eyes that appear to have one eyelid fold rather than a double lid. Also called epicanthal folds, they are common in people of East Asian heritage.

Monolids are formed by a piece of skin on the eyelid that runs from the nose to the eyebrow and gives the eyelid the appearance of having no crease. In some cases, it can make the eyelid more prominent, creating a more narrow appearance in the eye.

Monolids are normal and do not affect vision on their own. If a monolid is caused by a medical condition like Down syndrome, it could be linked with other eye troubles.

This article explains how monolids appear, genetic causes, and possible ways to minimize the appearance of monolids.

Anatomy

To understand monolids, it’s helpful to know a bit about eye anatomy. Human eyes have both upper and lower eyelids. The upper and lower eyelids meet at the corners of the eyes, an area known as the canthus. Most people have a visible crease in the upper lid, which gives the upper eyelid the appearance of having two sections. This is known as a double lid.

People who have a monolid have an epicanthal fold. This piece of skin covers the inner corner of the eye, reducing or eliminating the appearance of an eyelid crease. Monolids can make the upper eyelid appear puffier or give the appearance of narrow eyes.

Asian Descent

About 50% of people of Asian descent have a monolid. This type of eye shape is most common in people of East Asian descent.

Particularly, monolids are common among those who hail from these countries:

• China
• Korea
• Mongolia
• Japan

The epicanthal fold is caused by a genetic variation in the chromosomal make-up of people who originate from these regions, When East Asians do have an eyebrow crease, it’s often less prevalent than the eyebrow crease of Caucasians.

Scientists don’t fully understand why Asian people developed monolids. There is a theory that the monolid gave people an adaptive advantage when ancient Asians were living in cold and windy climates like Mongolia. The monolids may have offered people better eye protection. However, this is a theory; scientists don’t know for sure if this is why Asians have a monolid.

Medical Conditions

Monolids may affect non-Asian people. However, it's rare and is most specifically related to a medical condition. Medical conditions that can cause a monolid in people of any ethnicity include the following.

Down Syndrome

Also known as trisomy 21, this is a genetic disorder in which a person is born with an extra full or partial chromosome 21. Symptoms of Down syndrome can include a variety of physical characteristics, which often include monolids. It also may lead to medical conditions such as heart conditions or intellectual and developmental disabilities.

Fetal Alcohol Syndrome

Fetal alcohol syndrome occurs when a fetus is exposed to alcohol in utero. The effects can cause a wide range of medical problems and mental disabilities. It can also cause facial and physical abnormalities. The formation of epicanthal folds, in these instances, is considered abnormal.

Turner Syndrome

Turner syndrome is a genetic condition in which genetic females do not have a complete pair of chromosomes in some or all of their body cells. This causes physical characteristics such as very short stature and may result in monolids.

PKU Syndrome

As a genetic disorder, PKU is passed down from both parents to children. It manifests as a metabolic disorder in which the body cannot completely break down the protein (amino acid) phenylalanine. Thus, people with PKU must follow a special diet to avoid severe complications. Those born with the condition may have monolids or other identifiable physical characteristics.

Blepharophimosis

Known as BPES, blepharophimosis is a rare developmental disorder. Prominent facial features are usually present. In addition to monolids, these include narrow eyes, skin in the lower eyelids, and widely set eyes.

Williams Syndrome

Williams Syndrome is a genetic disorder that can cause developmental delays, heart problems, low muscle tone, and attention disorders. People with Williams Syndrome also tend to have unique facial traits such as a flat nasal bridge, prominent lips, and epicanthal folds.

Noonan Syndrome 

With this rare disorder, a person's eyes may slant downward and appear to wrap around the sides of the face. Monolids are also common. Noonan syndrome results from four genetic abnormalities and affects a person in more ways than physical appearance.

Zellweger Syndrome 

Zellweger syndrome is a rare metabolic disorder that is inherited. It affects almost all cells in the body, which can lead to various medical complications. Those affected by the syndrome may have facial abnormalities such as high foreheads and flattened brows. They may also have epicanthal folds.

Other Conditions

In addition to genetic conditions and inherited traits, other conditions can affect eyelids. While they may seem similar to epicanthal folds, they are different. These conditions include:

Ptosis: Ptosis refers to a condition in which the upper eyelids droop over the eye. It may be congenital (present at birth) or it might come about due to injury or aging.

Hooded eyes: Known as dermatochalasis, this is a condition in which excess skin bags down over the eyelid. It can cause some vision obstruction. It may be inherited, but it also occurs naturally with aging.

Creating a Crease

There is nothing wrong with having a monolid, and many people embrace this eye shape. But some others want eyes that appear to have a double lid and wider eyes. This can be done with makeup, adhesives, or surgery. If you are unhappy with your eye shape, you can try these, but remember that monolid eyes are beautiful just as they are.

Makeup

Asian makeup artists have their own tips and tricks to make monolid eyes look bigger or give the appearance of a crease. Eyeshadows and eyeliner can be used to draw attention to the eyes, making them more of a focal point on the face, even if they are narrow. Using bright colors, particularly on the inner eye, can help make a monolid eye pop, makeup artists say.

Tape or Glue

Some people with monolids choose to use tape or glue to give the appearance of having a double lid. The adhesives are meant to create an artificial crease in the eye temporarily, giving it the appearance of a double lid or wider eye.

Some people find eyelid tape or glue difficult to use and uncomfortable. The tape can make it more difficult to blink and affect tear production, all of which can have an impact on eye health.

Surgery (Blepharoplasty)

In order to permanently change the look of a monolid, some people opt for surgery to create a double lid. This type of surgery is known as blepharoplasty. The specific type of procedure most often used for people with monolids is double eyelid surgery.

During a blepharoplasty to change the appearance of a monolid, a doctor will create a crease in the eyelid, giving it the double lid appearance, and remove excess skin on the eyelid. This can be combined with a procedure known as ptosis surgery, which strengthens the eyelid muscle, giving a more wide-eyed appearance.

Summary

Monolids are part of the normal variation of human appearance. They are usually caused by your genetics but can also be caused by medical conditions. This eye shape doesn't impact your vision and is an example of a beautiful facial trait. In some instances and cultures, though, monolids are not preferred. In these cases, individuals may opt to lessen the appearance of a monolid with make-up or adhesives. There are also surgical ways to create a crease for the eye.

A Word From Verywell

It’s natural to be uncomfortable with a part of your body. If you dislike your monolid eyes, try to remember that having an eyelid with no crease is entirely normal and beautiful. Of course, that’s not always easy when there is an emphasis on Caucasian beauty standards.

If you want to change the appearance of your eyes, temporarily or permanently, be sure to consider the medical and emotional benefits and drawbacks. Ultimately, you’re the only one who can decide how comfortable you are with your eye shape and whether embracing it or changing it is right for you.