Dry Eye Syndrome Causes and Classification (Agenda Series Part.02-1)

“The cause of dry eye syndrome”

Hello, this is easy-to-understand ophthalmology story.

This time, the second part of the agenda series.

Let’s look at the causes and classification of dry eye syndrome .

Appropriate classification and treatment are different depending on the cause.

For this reason, it is necessary to know the cause and classification for optimal treatment for each patient.

What is dry eye syndrome?

Before examining the causes and classification of dry eye syndrome

Let’s go through the definition of what exactly dry eye syndrome is .

With advances in medicine and science, the concept and definition of dry eye syndrome has changed.


Dry eye syndrome was defined as follows.

“Insufficient tears and tear film disorders due to excessive evaporation of tears”

early 2000’s

“Diseases of the tear film and the ocular surface due to various causes” were defined as the main factors, especially increased osmotic pressure of tears and inflammation of the ocular surface .


Recently, it has been defined as “ocular surface disorders due to instability of the tear film due to various causes” , emphasizing the role of tears, that is, the tear film , in dry eye syndrome.

Causes of dry eye syndrome - tear film
tear film

The tear film refers to the layer of tears present on the surface of the eye, as above.

Tears are not just structures made up of water.

  1. oil layer

    Prevents the evaporation of tears from the most surface

  2. moisture layer

    It exists under the oil layer and provides moisture.

  3. mucin layer

    It is located between the cornea and the water layer.
    Make sure it adheres well to the cornea.

Dry eye syndrome is a disease in which the tear film differs from normal due to various causes .

Let’s see what could be the cause.

Causes of dry eye

Various tissues of the eye play a role to form a normally stable tear film .

  • lacrimal gland
  • eyelid
  • meibomian gland
  • conjunctiva
  • cornea

Even one problem can cause dryness, and most have multiple causes.

lacrimal gland

The lacrimal gland is the tissue that lies under the skin on the outer part of the upper eyelid.

lacrimal gland - dry eye
lacrimal tract

It is the tissue that produces the component of the water layer in the tear film.

If the lacrimal glands are damaged, tears cannot form and dry eyes occur.

Lacrimal gland tissue can be damaged during chemotherapy (radiation) or autoimmune disease (Sjogren’s).


The eyelids clean and lubricate the ocular surface by blinking .

Eyelashes act to block dust and foreign substances from the outside.

As you age or the shape of your eyelids changes due to trauma, you may not be able to protect the surface of your eyes normally, resulting in dry eye syndrome .

Valvavar and valgus- Causes of dry eye syndrome
ptosis and valgus valgus

Typically, there are valgus where the eyelids are rolled inward, and valgus valgus , where the eyelids are rolled outward.

Normally, an average of 15 to 20 blinks per minute is required .

Dry Eye Syndrome Causes and Classification (Agenda Series Part.02-1)

Concentrating on the screen, such as working on a computer or reading , involuntarily reduces blinking .

Blinks less frequently and can lead to dry eyes.

Maybom Line

This is a rather unfamiliar word.

It is a kind of oil gland (sebaceous gland) that exists in the eyelid along the hair root where eyelashes grow.

Meibomian gland - causes of dry eye syndrome
Maybom Line

The meibomian gland secretes an oil component called meibum .


Meibom constitutes the oil layer, which is the most surface of the tear film.

Meibom and the tear layer
Meibom and the tear layer

It is secreted with blinking, and the top of the tear layer is coated with oil as shown in the picture above.

Just like oily cosmetics that keep moisture for a long time

It helps the tears spread evenly on the surface of the eyeball and prevents them from evaporating quickly.

If the meibomian gland is blocked or inflamed and the secretion of oil is not smooth, dry eye syndrome occurs.

unhealthy meibomian gland
unhealthy meibomian gland

It is also the most common cause of dry eye syndrome .


The conjunctiva is a thin, opaque membrane overlying the white part .


As shown above, it is a part of the opaque conjunctiva that can be seen when the eyelid is turned upside down.

The conjunctiva contains cells called “goblet cells” .

Here, “mucin”, the innermost component of the tear layer, is secreted to keep the tear layer evenly attached to the surface of the eyeball .

Like a primer to apply before makeup?

When goblet cells are reduced, mucin secretion is reduced and dry eye syndrome can occur.

Typically, contact lenses or vitamin A deficiency are the causes of goblet cell reduction .


The cornea is the most important tissue in the symptoms of black pupil transparent dry eye syndrome.

The cornea, the only transparent tissue in our body [Link]


After all, the eyelids, tears, and conjunctiva exist to make the corneal surface smooth and smooth.

The cornea is a very sensitive tissue with innervation several hundred times that of the skin.

Due to this sensitive innervation of the cornea, appropriate tears are always secreted to maintain moisture in the cornea.

However , viral keratitis, severe diabetes, and prolonged use of eye drops blunt the cornea.

“Herpes keratitis”, click if you want to know more – Keratitis Part 3 [Link]

The cornea loses sensation , which reduces tear production and even reduces blinking, which can lead to dry eye syndrome .

vicious circle

I found out that dry eye syndrome can be caused by so many different causes .

The problem is that when one of the above problems occurs, other problems occur one after another .

In the end, we fall into a vicious cycle that is difficult to get out of once we enter, and it continues to aggravate and improve, tormenting us.

The vicious cycle of dry eye syndrome
The vicious cycle of dry eye syndrome

Dry eye syndrome can begin at any point in the gastric cycle.

Dry Eye Syndrome Causes and Classification (Agenda Series Part.02-1)

Above is a graph showing the progression of dry eye syndrome.

The first vicious cycle begins and until the asymptomatic threshold is crossed, there are no symptoms and no action is taken and it is left unattended.

But at some point, symptoms start and get worse.

Putting out the fire urgently with acute treatment according to the cause,

Dry eye syndrome can be controlled to some extent by properly controlling symptoms with maintenance treatment.

Unfortunately, dry eye syndrome is a disease that cannot be cured and must be managed for life .


So far, we have looked at the various causes of dry eye syndrome.

Originally, I was going to post a classification according to the cause, but it got too long, so I will cover the classification in the next post .

through this post

I hope that you feel that dry eye syndrome is such a complex disease and that you need correct treatment according to the cause.

Thanks for reading this long post,

Please use the community .

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