What Are Monolid Eyes?

Introduction

Monolids are one shape of the upper eyelid where there is no crease. It is most commonly seen in those of East Asian descent, although it can affect other ethnicities and is a common feature in some genetic disorders. A majority of people have what is referred to as double eyelids, where there is a crease in the eyelid. It is important to understand that monolids usually have no adverse health effects and are not any less beautiful than other eye shapes. Many methods have been developed to artificially create the crease, but these are for purely aesthetic purposes. Regardless of eye shape, it is important to maintain good eye hygiene practices to prevent any eye infections.

Anatomy of the eyelid

The eyelid is the thinnest skin of the whole body, less than 1mm thick. Underneath this delicate, thin layer of skin, the eye is protected by tissue, fat, and muscle. Within these layers there are glands and hair follicles from where the eyelashes grow. All these different components help keep the eye protected from outside debris.¹ 

The crease on the top of the eyelid is referred to as the superior palpebral sulcus and often lies 8-11mm above the rim of the upper eyelid. What determines where this crease lies depends on how long the levator aponeurosis fibres (a tissue that connects the levator palpebrae superioris muscle to the connective tissue of the eyelid, causing the muscle to lift the upper eyelid) are.¹ 

Causes of monolids

Monolids are mostly caused by genetics related to ethnic descent. Just as genetics determines your hair or eye colour, genetics often dictates the shape of your eyes and eyelids. While not exclusive to East Asian people, monolids are a common feature amongst people of East Asian descent, occurring in around 50% of the population.² 

Monolids are also common in infants whose nose bridges have yet to rise and fully develop.³ 

Some factors that contribute to the appearance of monolids include:

• Muscular differences - depending on the prominence or configuration of the main muscle that lifts the eyelid, the appearance of the crease can go unnoticed
• Fat distribution - fat distribution of the upper eyelid can control the appearance of the eyes. With less fat, it can give an appearance of sunken eyes and, for some people with monolids, an even distribution of fat across the lid can contribute to the appearance
• Epicanthic folds - a fold on the upper eyelid that covers the inner corner of the eye and is associated with having monolids³
• Genetic factors - genetics can play a role in two ways, a trait that is passed down through ethnic heritage, or through inherited conditions or genetic mutations 

There are some conditions that can cause one to have monolids regardless of their ethnic descent. These include:

• Down Syndrome
• Fetal alcohol syndrome
• Blepharophimosis-ptosis-epicanthus inversus syndrome (BPES)
• Rubinstein-Taybi syndrome
• Noonan syndrome
• Williams syndrome
• Phenylketonuria

BPES is a condition where there is a deformation of the eyelids. One gene specifically, FOXL2, is known to influence BPES. In the general population, BPES statistically occurs once in every 50,000 people. There are two main types of BPES, type I expresses more symptoms of primary ovarian insufficiency and type II exclusively manifests as eyelid malformations.⁴ 

Effect of monolids on vision and health

Most people with monolids do not have any issues with vision. However, some cases lacking an eyelid crease can result in what is called a hooded eyelid – where part of the eyelid folds over and blocks your vision. In these cases, there is nothing wrong with the eye itself, but the eyelid obstructs your view, and decreases your visual field or peripheral perception.⁵ 

People with monolids are no more likely to have eye infections than any other eye shape. Eye infections and dirt accumulation can happen with any eye shape and depend mostly on hygiene, environment, and lifestyle. 

Regardless of eyelid shape, you should always practice good eyelid hygiene to avoid infections. This includes: 

• Washing your eyelids with a gentle cleanser 
• Drying eyes with a clean towel 
• Avoiding rubbing your eyes 
• Removing makeup before bed 
• Avoiding sharing eye makeup

Monolids vs hooded eyes

Hooded eyelids are often confused with monolids but they differ in a few key parts. While hooded eyelids can also be attributed to genetics, they can also occur with age. Hooded eyelids are where there is a fold that covers the entire eyelid. It can also droop to block the person’s vision.

Surgery

Although not a medical necessity, some people choose to get aesthetic cosmetic surgery to create double eyelids, called blepharoplasty. In Asia, it is the most common cosmetic surgery.² 

This surgery dates back as far as 1896 in Japanese medical literature. Over time, the parameters of surgery changed based on the Western influence of the standard of beauty. As the decades progressed, the techniques developed to also give the patient deeper-set eyes along with the double eyelid shape.² 

There are many methods of creating the double eyelid, and cosmetic surgeons can recommend many options depending on the initial eyelid condition and shape, and the desired shape. This includes: 

• Suture fixation - the surgeon uses sutures (also called stitches) in the eyelid to encourage the eyelid to create a crease in response to the scarring. Often sutures are left for less than a week but some current methods use permanent sutures. This technique is often used for the short recovery time and because it is a less invasive option
• Skin-levator-skin incision - in this technique, a suture is placed in the tissue (levator aponeurosis) that connects the muscle (levator muscle) to the connective tissue in the upper eyelid to create a small crease
• Levator aponeurosis border to inferior subcutaneous plane incision - in this technique, a suture is placed from the muscle responsible for opening the eye to the fat under the eyelid to create a deeper crease²

Incisional techniques are believed to create longer-lasting results.²

There are other less permanent ways to create the illusion of a double eyelid using makeup or adhesives, for example:

• Eyeliners or eyeshadows - used to give the illusion of a crease when a darker shade is used at the desired area for the crease
• Special eyelid tape - a thin, crescent-shaped sliver of tape that goes on the eyelid to make the skin crease at that position
• Eyelid/eyelash glue - using this glue causes the skin to become tacky and “glue” the skin into the fold. 

These methods are not for everyone, especially those with sensitive skin. It is important that if you do use these methods to maintain proper eye hygiene before and after using them, and to make sure to use products specific for the eyelid. 

In most cases, monolids do not cause any health issues, and many embrace their eyelid shapes and even highlight them with different styles of makeup. All eye shapes are beautiful and unique with no superiority of one shape over the other.

Summary

Monolids are a type of eyelid shape where there is no visible crease of the upper eyelid. Largely associated with those of Asian descent, monolids are a common feature of approximately 50% of the East Asian population, however, this eye shape can appear in any ethnic group. There are also a number of conditions, such as Down syndrome, foetal alcohol syndrome, and noonan syndrome that have monolids as a characteristic feature. Monolids do not affect the health of the person and are a common eyelid shape — however, at times this shape can be associated with impaired vision, from the eyelid folding over the eye. While not a medical necessity, surgery to create a double fold is the most popular aesthetic cosmetic surgery in Asia. There are a number of surgical procedures that will create a double fold. For some less permanent and invasive ways to create the double crease look, makeup and adhesives can be used just to create the illusion of a crease. While there are these techniques to create an eyelid crease, do not feel pressured to conform to them if you do not wish to. There is no superior eyelid shape to others and all eye and eyelid shapes are beautiful and should be embraced!