Dry eye syndrome examination, past and present (Agenda series Part.04)

“Test for dry eye syndrome”

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

In the last post, we looked at how to test for dry eye symptoms (OSDI questionnaire).

We emphasized that dry eye syndrome is a disease in which symptoms are the key.

Today, we are going to learn about the ophthalmic examination method for dry eye syndrome in earnest.

Recently, new diagnostic technologies are emerging day by day.

However, what is certain is that there is no way to know for sure at once whether or not dry eye syndrome is present.


The past of dry eye examination

With the advent of new diagnostic methods

Many of the low-accuracy and poorly reproducible inspection methods of the past are obsolete.

However, the two essential test methods based on the argument that dry eye syndrome is mainly caused by insufficient tear secretion and excessive evaporation of tears are still widely used due to their simplicity and low cost.

“Shimmer Test” to measure the degree of tear secretion

It will be the “tear film destruction time” that measures the evaporation of tears .


Shimmer test

The Schirmer test or Schirmer test is a test method created in 1903 by Schirmer, a German ophthalmologist.

It’s a very intuitive and easy way to test if you’re making the right amount of tears .

Dry Eye Test - Shimmer Test
Shimmer test

As shown in the figure, a fixed length of filter paper (paper) is hung on the lower eyelid to measure the amount of tears secreted for 5 minutes .

Shimmer test results
Shimmer test results

As shown in the picture, you can measure the length of the wet part of the measuring paper to know the degree of tear secretion, right?

It is widely used as a very simple and intuitive test method, but it has the disadvantage that the test results do not match or show different results depending on the inspector .

Also, there is a point that it may include tear secretion caused by stimulation of the test strip rather than natural tear secretion.

However, it is a widely used test method with various modifications such as testing after using eye drops anesthetic.


Tear film breakdown time (TBUT)

This is a method of measuring Tear Film Break Up Time in English, that is , the time at which the tear film is broken.

I explained that the tear film consists of three layers .

Dry eye syndrome examination, past and present (Agenda series Part.04)
tear layer

If the oil layer on the most surface does not do its job, the tears evaporate quickly and the tear film is destroyed .

Measurement of tear film break-up time is an easy way to test if you have a special dye and an ophthalmic microscope .

Measurement of tear film breakdown time
Measurement of tear film breakdown time

The picture above is a test strip with a fluorescent substance (dye) called “fluorescein” .

There is a method to drop the solution directly into the eye, but there is also a method to moisten the test strip and apply it to the eye as shown in the picture.

After that, blink your eyes and the dye will spread evenly across the cornea.

VARPA Group
tear film break time

When observed under special light under a microscope, the dye will turn green.

As shown in the picture on the left, if the tears evaporate after a certain period of time in a state in which the corneal surface is stained evenly , empty spaces with staining are visible as shown in the picture on the right .

The method to measure the time between these times is “Measurement of tear film breakage time”.

Normally, it takes about 15 to 34 seconds , but in dry eyes, the tear film is destroyed in less than 10 seconds .

Dry Eye Test - Severe Dry Eye TBUT
Severe dry eye syndrome TBUT

In the case of severe dry eye syndrome, you can see that the tear film is destroyed in a very irregular shape within a few seconds as shown in the picture.

However, this test is also not an accurate test because the results may vary depending on the tester and the amount of dye added.


The shimmer test measures the amount of tears secreted and can diagnose tear-deficient dry eye syndrome .

The TBUT test is a good method for diagnosing evaporative dry eye syndrome by measuring the time the tears evaporate.

Although both have the disadvantage of being unreliable, they are still widely used methods because they are cheap and very convenient .


Current status of dry eye examination

Recently, there are many different test methods for dry eye syndrome.

There are two major types of imaging tests and tear component analysis.

Let’s take a look at the typical inspections.

  • radiology examination

    -Anterior segment optical coherence tomography (AS-OCT)

    – Corneal topography

    -Meibomian gland morphology test

  • tear component analysis

    -osmotic pressure test

    -Measurement of inflammatory components (MMP-9)

osmotic pressure test

We explained that the increase in tear osmotic pressure is an important factor in dry eye syndrome.

Through a vicious cycle, the water content of tears decreases and the osmotic pressure increases.

If so, can you easily know if you have dry eye syndrome by measuring the osmotic pressure of your tears?

In the past, measuring tear osmotic pressure was a difficult method, but now it can be measured with a very simple method.

Dry Eye Test - Tear Osmosis Measurement
tear osmotic pressure measurement

It is a tool that can check the osmotic pressure by simply bringing the tip of a pen-like tool to the tears.

It’s like measuring blood sugar, isn’t it?

If the tear osmolarity is higher than 308, it can be thought to be due to dry eye syndrome .

Or, even if the two eyes show a significant difference, you may be suspicious.

Osmolarity measurement of tears is a useful test tool due to its high accuracy and reproducibility (similar results even if repeated) .


Inflammatory component measurement (MMP-9)

Dry eye syndrome is a disease caused by various factors, so it is necessary to examine various factors .

In addition to the rise in tear osmotic pressure, one of the main factors is the presence or absence of inflammation .

There are various inflammatory components that can detect inflammation of the ocular surface, but “MMP-9 ” is a substance that is easy to measure and shows the inflammatory state well.

MMP-9 levels increase in dry eye syndrome, causing instability of the tear film and reducing the barrier function of the cornea .

Therefore , the presence or absence of dry eye syndrome can be determined by measuring the concentration of MMP-9 in tears .

MMP-9 Measurement
MMP-9 Measurement

You can easily find out the concentration of MMP-9 by using a stomach test kit that looks like a pregnancy test.

Dry eye syndrome examination, past and present (Agenda series Part.04)
MMP-9 negative and positive

Although it is not possible to know the exact number, you can know whether it is above or below the standard concentration of 40 ng/ml as shown in the above result.

As such, knowing the presence or absence of inflammation in dry eye syndrome has very important significance not only in diagnosis but also in the direction of treatment .

As I will post later, it is because it decides whether to use anti-inflammatory treatment or not .


Anterior segment optical coherence tomography

Optical coherence tomography is easily expressed as eye CT, and the main examination instrument is a detailed examination of the retina, the tissue behind the original eye.

However, it is also used to test for dry eye syndrome because the anterior segment of the eye, such as tears, eyelids, and cornea, can be observed in high resolution.

tear strip height
tear strip height

It is to check the height of the tear duct.

As shown in the figure above, the tear band refers to the height of the tears pooling at the point where the eyelids and cornea meet.

If there are not enough tears, the height of the tear strip will also be lowered.

Measurement of tear striae height using OCT
Measurement of tear striae height using OCT

As shown in the figure, using eye CT, the height of the lacrimal striae can be accurately measured.


meibomian gland morphology

This is a test to see if there is a problem with the meibomian gland, which is the main cause of evaporative dry eye syndrome.

meibom gland
meibom gland

Meibomian glands are located on the upper and lower eyelids and are a kind of oil gland that forms the oil film of the tear layer .

Insufficient oil formation results in evaporative dry eye syndrome, in which tears dry quickly.

The existing evaluation method for meibomian glands was to directly observe the entrance to the gland to see if there was any blockage or inflammation.

meibomian gland disorder
meibomian gland disorder

Meibography is a machine that can directly observe the shape or structure of meibomian glands.

normal meibomian gland
normal meibomian gland

Normal meibomian glands seen through meibography are densely arranged along the eyelids as shown in the figure.

meibomian gland disorder
meibomian gland disorder

Meibomian glands may be blocked due to drainage disorders, causing swelling of the meibomian glands, or even loss of meibomian glands due to severe inflammation.

As such, the morphology test is useful because it allows you to directly see the current state of the meibomian gland, but the functional part is unknown, so it needs to be interpreted like other tests .

Meibomian glands can be tested using a variety of machines.

Dry eye examination - meibography using infrared and OCT
Meibography using infrared and OCT

Typically, the examination can be performed using the infrared method on the left and the eye CT (right) described above.

It can also be seen through the corneal topography, which will be described later.


corneal topography

The corneal topography test is literally an instrument for examining the topography and shape of the cornea.

However , it is a good device that does not irritate the eyes by using infrared rays and can test tear film destruction time, tear striae height, and meibomian gland morphology .

Dry Eye Test - K5M
Corneal Topography Checker

As shown in the figure, it is a type of inspection device composed of several concentric circles.

A typical example is the keratograph 5M, or K5M for short.

TBUT measurement
TBUT measurement

Tear film breakdown time (TBUT) can be measured as above.

Unlike conventional TBUT measurement, there is less stimulation and no bright light is required for the examination, so the examination can be performed in a more comfortable state for the patient. The results will also be more reliable.

Lacrimal gland height and meibomian gland test
Lacrimal gland height and meibomian gland test

In addition, it has the advantage of being able to test the eye waterline (TMH) and meibomian glands described above with one machine .


Imaging inspection using the latest equipment is meaningful in that it overcomes the limitations of the previously unreliable inspection methods to some extent.

The shimmer test to see the tear secretion is a tear band height test.

TBUT that sees evaporation is a method using an imaging device from a method through a dye..

Nevertheless, since there is no perfect and definitive test method, it is necessary to comprehensively judge the results of various tests focusing on the patient’s symptoms .


concluding

We learned about the past and present of abnormal dry eye examination.

Are there many different types of tests?

It is not necessary to do all the tests described.

When you look at your patients, each doctor develops a diagnosis that he or she prefers and believes in.

This is why different doctors and hospitals have slightly different methods of diagnosing dry eye syndrome.

It can be said that there is no definitive diagnostic method for dry eye syndrome, that is, the Gold Standard Test.

In the next post, we will learn about “treatment of dry eye syndrome” in earnest.

Treatment has also undergone numerous revisions, and new drugs and new treatments are still in progress.

Thanks for reading this long post,

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